[PATCH v13] Make int4 and int8 operations more efficent

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[PATCH v13] Make int4 and int8 operations more efficent
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* [PATCH v13] Make int4 and int8 operations more efficent
@ 2019-09-15 07:06  David Fetter <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: David Fetter @ 2019-09-15 07:06 UTC (permalink / raw)


- Output routines now do more digits per iteration, and
- Add code which determines the number of decimal digits in an int4/int8 efficiently
- Split off pg_ultoa_n from pg_ltoa
- Use same to make other functions shorter
- Change some of the functions to take only unsigned so they don't have to branch for negative numbers

diff --git a/src/backend/access/common/printsimple.c b/src/backend/access/common/printsimple.c
index 651ade14dd..5c5b6d33b2 100644
--- a/src/backend/access/common/printsimple.c
+++ b/src/backend/access/common/printsimple.c
@@ -112,7 +112,7 @@ printsimple(TupleTableSlot *slot, DestReceiver *self)
 			case INT8OID:
 				{
 					int64		num = DatumGetInt64(value);
-					char		str[23];	/* sign, 21 digits and '\0' */
+					char		str[MAXINT8LEN + 1];
 
 					pg_lltoa(num, str);
 					pq_sendcountedtext(&buf, str, strlen(str), false);
diff --git a/src/backend/utils/adt/datetime.c b/src/backend/utils/adt/datetime.c
index e38bd93054..9fb03d4fbc 100644
--- a/src/backend/utils/adt/datetime.c
+++ b/src/backend/utils/adt/datetime.c
@@ -391,9 +391,9 @@ AppendSeconds(char *cp, int sec, fsec_t fsec, int precision, bool fillzeros)
 	Assert(precision >= 0);
 
 	if (fillzeros)
-		cp = pg_ltostr_zeropad(cp, Abs(sec), 2);
+		cp = pg_ultostr_zeropad(cp, Abs(sec), 2);
 	else
-		cp = pg_ltostr(cp, Abs(sec));
+		cp = pg_ultostr(cp, Abs(sec));
 
 	/* fsec_t is just an int32 */
 	if (fsec != 0)
@@ -433,7 +433,7 @@ AppendSeconds(char *cp, int sec, fsec_t fsec, int precision, bool fillzeros)
 		 * which will generate a correct answer in the minimum valid width.
 		 */
 		if (value)
-			return pg_ltostr(cp, Abs(fsec));
+			return pg_ultostr(cp, Abs(fsec));
 
 		return end;
 	}
@@ -3834,20 +3834,20 @@ EncodeTimezone(char *str, int tz, int style)
 
 	if (sec != 0)
 	{
-		str = pg_ltostr_zeropad(str, hour, 2);
+		str = pg_ultostr_zeropad(str, hour, 2);
 		*str++ = ':';
-		str = pg_ltostr_zeropad(str, min, 2);
+		str = pg_ultostr_zeropad(str, min, 2);
 		*str++ = ':';
-		str = pg_ltostr_zeropad(str, sec, 2);
+		str = pg_ultostr_zeropad(str, sec, 2);
 	}
 	else if (min != 0 || style == USE_XSD_DATES)
 	{
-		str = pg_ltostr_zeropad(str, hour, 2);
+		str = pg_ultostr_zeropad(str, hour, 2);
 		*str++ = ':';
-		str = pg_ltostr_zeropad(str, min, 2);
+		str = pg_ultostr_zeropad(str, min, 2);
 	}
 	else
-		str = pg_ltostr_zeropad(str, hour, 2);
+		str = pg_ultostr_zeropad(str, hour, 2);
 	return str;
 }
 
@@ -3864,40 +3864,40 @@ EncodeDateOnly(struct pg_tm *tm, int style, char *str)
 		case USE_ISO_DATES:
 		case USE_XSD_DATES:
 			/* compatible with ISO date formats */
-			str = pg_ltostr_zeropad(str,
+			str = pg_ultostr_zeropad(str,
 									(tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);
 			*str++ = '-';
-			str = pg_ltostr_zeropad(str, tm->tm_mon, 2);
+			str = pg_ultostr_zeropad(str, tm->tm_mon, 2);
 			*str++ = '-';
-			str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
+			str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
 			break;
 
 		case USE_SQL_DATES:
 			/* compatible with Oracle/Ingres date formats */
 			if (DateOrder == DATEORDER_DMY)
 			{
-				str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
+				str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
 				*str++ = '/';
-				str = pg_ltostr_zeropad(str, tm->tm_mon, 2);
+				str = pg_ultostr_zeropad(str, tm->tm_mon, 2);
 			}
 			else
 			{
-				str = pg_ltostr_zeropad(str, tm->tm_mon, 2);
+				str = pg_ultostr_zeropad(str, tm->tm_mon, 2);
 				*str++ = '/';
-				str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
+				str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
 			}
 			*str++ = '/';
-			str = pg_ltostr_zeropad(str,
+			str = pg_ultostr_zeropad(str,
 									(tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);
 			break;
 
 		case USE_GERMAN_DATES:
 			/* German-style date format */
-			str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
+			str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
 			*str++ = '.';
-			str = pg_ltostr_zeropad(str, tm->tm_mon, 2);
+			str = pg_ultostr_zeropad(str, tm->tm_mon, 2);
 			*str++ = '.';
-			str = pg_ltostr_zeropad(str,
+			str = pg_ultostr_zeropad(str,
 									(tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);
 			break;
 
@@ -3906,18 +3906,18 @@ EncodeDateOnly(struct pg_tm *tm, int style, char *str)
 			/* traditional date-only style for Postgres */
 			if (DateOrder == DATEORDER_DMY)
 			{
-				str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
+				str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
 				*str++ = '-';
-				str = pg_ltostr_zeropad(str, tm->tm_mon, 2);
+				str = pg_ultostr_zeropad(str, tm->tm_mon, 2);
 			}
 			else
 			{
-				str = pg_ltostr_zeropad(str, tm->tm_mon, 2);
+				str = pg_ultostr_zeropad(str, tm->tm_mon, 2);
 				*str++ = '-';
-				str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
+				str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
 			}
 			*str++ = '-';
-			str = pg_ltostr_zeropad(str,
+			str = pg_ultostr_zeropad(str,
 									(tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);
 			break;
 	}
@@ -3942,9 +3942,9 @@ EncodeDateOnly(struct pg_tm *tm, int style, char *str)
 void
 EncodeTimeOnly(struct pg_tm *tm, fsec_t fsec, bool print_tz, int tz, int style, char *str)
 {
-	str = pg_ltostr_zeropad(str, tm->tm_hour, 2);
+	str = pg_ultostr_zeropad(str, tm->tm_hour, 2);
 	*str++ = ':';
-	str = pg_ltostr_zeropad(str, tm->tm_min, 2);
+	str = pg_ultostr_zeropad(str, tm->tm_min, 2);
 	*str++ = ':';
 	str = AppendSeconds(str, tm->tm_sec, fsec, MAX_TIME_PRECISION, true);
 	if (print_tz)
@@ -3987,16 +3987,16 @@ EncodeDateTime(struct pg_tm *tm, fsec_t fsec, bool print_tz, int tz, const char
 		case USE_ISO_DATES:
 		case USE_XSD_DATES:
 			/* Compatible with ISO-8601 date formats */
-			str = pg_ltostr_zeropad(str,
+			str = pg_ultostr_zeropad(str,
 									(tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);
 			*str++ = '-';
-			str = pg_ltostr_zeropad(str, tm->tm_mon, 2);
+			str = pg_ultostr_zeropad(str, tm->tm_mon, 2);
 			*str++ = '-';
-			str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
+			str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
 			*str++ = (style == USE_ISO_DATES) ? ' ' : 'T';
-			str = pg_ltostr_zeropad(str, tm->tm_hour, 2);
+			str = pg_ultostr_zeropad(str, tm->tm_hour, 2);
 			*str++ = ':';
-			str = pg_ltostr_zeropad(str, tm->tm_min, 2);
+			str = pg_ultostr_zeropad(str, tm->tm_min, 2);
 			*str++ = ':';
 			str = AppendTimestampSeconds(str, tm, fsec);
 			if (print_tz)
@@ -4007,23 +4007,23 @@ EncodeDateTime(struct pg_tm *tm, fsec_t fsec, bool print_tz, int tz, const char
 			/* Compatible with Oracle/Ingres date formats */
 			if (DateOrder == DATEORDER_DMY)
 			{
-				str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
+				str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
 				*str++ = '/';
-				str = pg_ltostr_zeropad(str, tm->tm_mon, 2);
+				str = pg_ultostr_zeropad(str, tm->tm_mon, 2);
 			}
 			else
 			{
-				str = pg_ltostr_zeropad(str, tm->tm_mon, 2);
+				str = pg_ultostr_zeropad(str, tm->tm_mon, 2);
 				*str++ = '/';
-				str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
+				str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
 			}
 			*str++ = '/';
-			str = pg_ltostr_zeropad(str,
+			str = pg_ultostr_zeropad(str,
 									(tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);
 			*str++ = ' ';
-			str = pg_ltostr_zeropad(str, tm->tm_hour, 2);
+			str = pg_ultostr_zeropad(str, tm->tm_hour, 2);
 			*str++ = ':';
-			str = pg_ltostr_zeropad(str, tm->tm_min, 2);
+			str = pg_ultostr_zeropad(str, tm->tm_min, 2);
 			*str++ = ':';
 			str = AppendTimestampSeconds(str, tm, fsec);
 
@@ -4046,16 +4046,16 @@ EncodeDateTime(struct pg_tm *tm, fsec_t fsec, bool print_tz, int tz, const char
 
 		case USE_GERMAN_DATES:
 			/* German variant on European style */
-			str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
+			str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
 			*str++ = '.';
-			str = pg_ltostr_zeropad(str, tm->tm_mon, 2);
+			str = pg_ultostr_zeropad(str, tm->tm_mon, 2);
 			*str++ = '.';
-			str = pg_ltostr_zeropad(str,
+			str = pg_ultostr_zeropad(str,
 									(tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);
 			*str++ = ' ';
-			str = pg_ltostr_zeropad(str, tm->tm_hour, 2);
+			str = pg_ultostr_zeropad(str, tm->tm_hour, 2);
 			*str++ = ':';
-			str = pg_ltostr_zeropad(str, tm->tm_min, 2);
+			str = pg_ultostr_zeropad(str, tm->tm_min, 2);
 			*str++ = ':';
 			str = AppendTimestampSeconds(str, tm, fsec);
 
@@ -4081,7 +4081,7 @@ EncodeDateTime(struct pg_tm *tm, fsec_t fsec, bool print_tz, int tz, const char
 			*str++ = ' ';
 			if (DateOrder == DATEORDER_DMY)
 			{
-				str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
+				str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
 				*str++ = ' ';
 				memcpy(str, months[tm->tm_mon - 1], 3);
 				str += 3;
@@ -4091,16 +4091,16 @@ EncodeDateTime(struct pg_tm *tm, fsec_t fsec, bool print_tz, int tz, const char
 				memcpy(str, months[tm->tm_mon - 1], 3);
 				str += 3;
 				*str++ = ' ';
-				str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
+				str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
 			}
 			*str++ = ' ';
-			str = pg_ltostr_zeropad(str, tm->tm_hour, 2);
+			str = pg_ultostr_zeropad(str, tm->tm_hour, 2);
 			*str++ = ':';
-			str = pg_ltostr_zeropad(str, tm->tm_min, 2);
+			str = pg_ultostr_zeropad(str, tm->tm_min, 2);
 			*str++ = ':';
 			str = AppendTimestampSeconds(str, tm, fsec);
 			*str++ = ' ';
-			str = pg_ltostr_zeropad(str,
+			str = pg_ultostr_zeropad(str,
 									(tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);
 
 			if (print_tz)
diff --git a/src/backend/utils/adt/int8.c b/src/backend/utils/adt/int8.c
index 0ff9394a2f..6230807906 100644
--- a/src/backend/utils/adt/int8.c
+++ b/src/backend/utils/adt/int8.c
@@ -27,8 +27,6 @@
 #include "utils/builtins.h"
 
 
-#define MAXINT8LEN		25
-
 typedef struct
 {
 	int64		current;
diff --git a/src/backend/utils/adt/numutils.c b/src/backend/utils/adt/numutils.c
index 70138feb29..27d6f3aacb 100644
--- a/src/backend/utils/adt/numutils.c
+++ b/src/backend/utils/adt/numutils.c
@@ -20,6 +20,68 @@
 
 #include "common/int.h"
 #include "utils/builtins.h"
+#include "port/pg_bitutils.h"
+
+/*
+ * A table of all two-digit numbers. This is used to speed up decimal digit
+ * generation by copying pairs of digits into the final output.
+ */
+static const char DIGIT_TABLE[200] =
+"00" "01" "02" "03" "04" "05" "06" "07" "08" "09"
+"10" "11" "12" "13" "14" "15" "16" "17" "18" "19"
+"20" "21" "22" "23" "24" "25" "26" "27" "28" "29"
+"30" "31" "32" "33" "34" "35" "36" "37" "38" "39"
+"40" "41" "42" "43" "44" "45" "46" "47" "48" "49"
+"50" "51" "52" "53" "54" "55" "56" "57" "58" "59"
+"60" "61" "62" "63" "64" "65" "66" "67" "68" "69"
+"70" "71" "72" "73" "74" "75" "76" "77" "78" "79"
+"80" "81" "82" "83" "84" "85" "86" "87" "88" "89"
+"90" "91" "92" "93" "94" "95" "96" "97" "98" "99";
+
+/*
+ * Adapted from http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog10
+ */
+static inline int
+decimalLength32(const uint32 v)
+{
+	int			t;
+	static uint32	PowersOfTen[] =
+	{1,                10,                100,
+	 1000,             10000,             100000,
+	 1000000,          10000000,          100000000,
+	 1000000000};
+	/*
+	 * Compute base-10 logarithm by dividing the base-2 logarithm
+	 * by a good-enough approximation of the base-2 logarithm of 10
+	 */
+	t = (pg_leftmost_one_pos32(v) + 1)*1233/4096;
+	return t + (v >= PowersOfTen[t]);
+}
+
+static inline int
+decimalLength64(const uint64 v)
+{
+	int			t;
+	static uint64	PowersOfTen[] = {
+		UINT64CONST(1),                   UINT64CONST(10),
+		UINT64CONST(100),                 UINT64CONST(1000),
+		UINT64CONST(10000),               UINT64CONST(100000),
+		UINT64CONST(1000000),             UINT64CONST(10000000),
+		UINT64CONST(100000000),           UINT64CONST(1000000000),
+		UINT64CONST(10000000000),         UINT64CONST(100000000000),
+		UINT64CONST(1000000000000),       UINT64CONST(10000000000000),
+		UINT64CONST(100000000000000),     UINT64CONST(1000000000000000),
+		UINT64CONST(10000000000000000),   UINT64CONST(100000000000000000),
+		UINT64CONST(1000000000000000000), UINT64CONST(10000000000000000000)
+	};
+
+	/*
+	 * Compute base-10 logarithm by dividing the base-2 logarithm
+	 * by a good-enough approximation of the base-2 logarithm of 10
+	 */
+	t = (pg_leftmost_one_pos64(v) + 1)*1233/4096;
+	return t + (v >= PowersOfTen[t]);
+}
 
 /*
  * pg_atoi: convert string to integer
@@ -276,116 +338,196 @@ pg_itoa(int16 i, char *a)
 }
 
 /*
- * pg_ltoa: converts a signed 32-bit integer to its string representation
+ * pg_ultoa_n: converts an unsigned 32-bit integer to its string representation,
+ * not NUL-terminated, and returns the length of that string representation
  *
- * Caller must ensure that 'a' points to enough memory to hold the result
- * (at least 12 bytes, counting a leading sign and trailing NUL).
+ * Caller must ensure that 'a' points to enough memory to hold the result (at
+ * least 10 bytes)
+ */
+int
+pg_ultoa_n(uint32 value, char *a)
+{
+	int		olength, i = 0;
+
+	/* Degenerate case */
+	if (value == 0)
+	{
+		*a = '0';
+		return 1;
+	}
+
+	olength = decimalLength32(value);
+
+	/* Compute the result string. */
+	while (value >= 10000)
+	{
+		const	uint32 c = value - 10000 * (value / 10000);
+		const	uint32 c0 = (c % 100) << 1;
+		const	uint32 c1 = (c / 100) << 1;
+
+		char *pos = a + olength - i;
+
+		value /= 10000;
+
+		memcpy(pos - 2, DIGIT_TABLE + c0, 2);
+		memcpy(pos - 4, DIGIT_TABLE + c1, 2);
+		i += 4;
+	}
+	if (value >= 100)
+	{
+		const uint32 c = (value % 100) << 1;
+
+		char *pos = a + olength - i;
+
+		value /= 100;
+
+		memcpy(pos - 2, DIGIT_TABLE + c, 2);
+		i += 2;
+	}
+	if (value >= 10)
+	{
+		const uint32 c = value << 1;
+
+		char *pos = a + olength - i;
+		memcpy(pos - 2, DIGIT_TABLE + c, 2);
+	}
+	else
+	{
+		*a = (char) ('0' + value);
+	}
+
+	return olength;
+}
+
+/*
+ * NUL-terminate the output of pg_ultoa_n.
+ *
+ * It is the caller's responsibility to ensure that a is at least 12 bytes long,
+ * which is enough room to hold a minus sign, a maximally long int32, and the
+ * above terminating NUL.
  */
 void
 pg_ltoa(int32 value, char *a)
 {
-	char	   *start = a;
-	bool		neg = false;
 
-	/*
-	 * Avoid problems with the most negative integer not being representable
-	 * as a positive integer.
-	 */
-	if (value == PG_INT32_MIN)
+	uint32	uvalue = (uint32)value;
+	int		len;
+	if (value < 0)
 	{
-		memcpy(a, "-2147483648", 12);
-		return;
-	}
-	else if (value < 0)
-	{
-		value = -value;
-		neg = true;
-	}
-
-	/* Compute the result string backwards. */
-	do
-	{
-		int32		remainder;
-		int32		oldval = value;
-
-		value /= 10;
-		remainder = oldval - value * 10;
-		*a++ = '0' + remainder;
-	} while (value != 0);
-
-	if (neg)
+		uvalue = (uint32)0 - uvalue;
 		*a++ = '-';
+	}
+	len = pg_ultoa_n(uvalue, a);
+	a[len] = '\0';
+}
+
+/*
+ * Get the decimal representation, not NUL-terminated, and return the length of
+ * same.  Caller must ensure that a points to at least MAXINT8LEN bytes.
+ */
+int
+pg_ulltoa_n(uint64 value, char *a)
+{
+	int	olength, i = 0;
+	uint32 value2;
+
+
+	/* Degenerate case */
+	if (value == 0)
+	{
+		*a = '0';
+		return 1;
+	}
+
+	olength = decimalLength64(value);
+
+	/* Compute the result string. */
+	while (value >= 100000000)
+	{
+		const	uint64 q = value / 100000000;
+		uint32	value2 = (uint32) (value - 100000000 * q);
+
+		const uint32 c = value2 % 10000;
+		const uint32 d = value2 / 10000;
+		const uint32 c0 = (c % 100) << 1;
+		const uint32 c1 = (c / 100) << 1;
+		const uint32 d0 = (d % 100) << 1;
+		const uint32 d1 = (d / 100) << 1;
+
+		char *pos = a + olength - i;
+
+		value = q;
 
-	/* Add trailing NUL byte, and back up 'a' to the last character. */
-	*a-- = '\0';
+		memcpy(pos - 2, DIGIT_TABLE + c0, 2);
+		memcpy(pos - 4, DIGIT_TABLE + c1, 2);
+		memcpy(pos - 6, DIGIT_TABLE + d0, 2);
+		memcpy(pos - 8, DIGIT_TABLE + d1, 2);
+		i += 8;
+	}
+
+	/* Switch to 32-bit for speed */
+	value2 = (uint32) value;
+
+	if (value2 >= 10000)
+	{
+		const	uint32 c = value2 - 10000 * (value2 / 10000);
+		const	uint32 c0 = (c % 100) << 1;
+		const	uint32 c1 = (c / 100) << 1;
+
+		char *pos = a + olength - i;
+
+		value2 /= 10000;
 
-	/* Reverse string. */
-	while (start < a)
+		memcpy(pos - 2, DIGIT_TABLE + c0, 2);
+		memcpy(pos - 4, DIGIT_TABLE + c1, 2);
+		i += 4;
+	}
+	if (value2 >= 100)
+	{
+		const uint32 c = (value2 % 100) << 1;
+		char *pos = a + olength - i;
+
+		value2 /= 100;
+
+		memcpy(pos - 2, DIGIT_TABLE + c, 2);
+		i += 2;
+	}
+	if (value2 >= 10)
 	{
-		char		swap = *start;
+		const uint32 c = value2 << 1;
+		char *pos = a + olength - i;
 
-		*start++ = *a;
-		*a-- = swap;
+		memcpy(pos - 2, DIGIT_TABLE + c, 2);
 	}
+	else
+		*a = (char) ('0' + value2);
+
+	return olength;
 }
 
 /*
  * pg_lltoa: convert a signed 64-bit integer to its string representation
  *
  * Caller must ensure that 'a' points to enough memory to hold the result
- * (at least MAXINT8LEN+1 bytes, counting a leading sign and trailing NUL).
+ * (at least MAXINT8LEN + 1 bytes, counting a leading sign and trailing NUL).
  */
 void
 pg_lltoa(int64 value, char *a)
 {
-	char	   *start = a;
-	bool		neg = false;
-
-	/*
-	 * Avoid problems with the most negative integer not being representable
-	 * as a positive integer.
-	 */
-	if (value == PG_INT64_MIN)
+	int len;
+	uint64 uvalue = value;
+	if (value < 0)
 	{
-		memcpy(a, "-9223372036854775808", 21);
-		return;
-	}
-	else if (value < 0)
-	{
-		value = -value;
-		neg = true;
-	}
-
-	/* Compute the result string backwards. */
-	do
-	{
-		int64		remainder;
-		int64		oldval = value;
-
-		value /= 10;
-		remainder = oldval - value * 10;
-		*a++ = '0' + remainder;
-	} while (value != 0);
-
-	if (neg)
 		*a++ = '-';
-
-	/* Add trailing NUL byte, and back up 'a' to the last character. */
-	*a-- = '\0';
-
-	/* Reverse string. */
-	while (start < a)
-	{
-		char		swap = *start;
-
-		*start++ = *a;
-		*a-- = swap;
+		uvalue = (uint64)0 - uvalue;
 	}
+	len = pg_ulltoa_n(uvalue, a);
+	a[len] = 0;
 }
 
 
 /*
- * pg_ltostr_zeropad
+ * pg_ultostr_zeropad
  *		Converts 'value' into a decimal string representation stored at 'str'.
  *		'minwidth' specifies the minimum width of the result; any extra space
  *		is filled up by prefixing the number with zeros.
@@ -407,62 +549,25 @@ pg_lltoa(int64 value, char *a)
  * result.
  */
 char *
-pg_ltostr_zeropad(char *str, int32 value, int32 minwidth)
+pg_ultostr_zeropad(char *str, uint32 value, int32 minwidth)
 {
-	char	   *start = str;
-	char	   *end = &str[minwidth];
-	int32		num = value;
+	int			len;
 
 	Assert(minwidth > 0);
 
-	/*
-	 * Handle negative numbers in a special way.  We can't just write a '-'
-	 * prefix and reverse the sign as that would overflow for INT32_MIN.
-	 */
-	if (num < 0)
+	if (value < 100 && minwidth == 2) /* Short cut for common case */
 	{
-		*start++ = '-';
-		minwidth--;
-
-		/*
-		 * Build the number starting at the last digit.  Here remainder will
-		 * be a negative number, so we must reverse the sign before adding '0'
-		 * in order to get the correct ASCII digit.
-		 */
-		while (minwidth--)
-		{
-			int32		oldval = num;
-			int32		remainder;
-
-			num /= 10;
-			remainder = oldval - num * 10;
-			start[minwidth] = '0' - remainder;
-		}
-	}
-	else
-	{
-		/* Build the number starting at the last digit */
-		while (minwidth--)
-		{
-			int32		oldval = num;
-			int32		remainder;
-
-			num /= 10;
-			remainder = oldval - num * 10;
-			start[minwidth] = '0' + remainder;
-		}
+		memcpy(str, DIGIT_TABLE + value * 2, 2);
+		return str + 2;
 	}
 
-	/*
-	 * If minwidth was not high enough to fit the number then num won't have
-	 * been divided down to zero.  We punt the problem to pg_ltostr(), which
-	 * will generate a correct answer in the minimum valid width.
-	 */
-	if (num != 0)
-		return pg_ltostr(str, value);
+	len = pg_ultoa_n(value, str);
+	if (len >= minwidth)
+		return str + len;
 
-	/* Otherwise, return last output character + 1 */
-	return end;
+	memmove(str + minwidth - len, str, len);
+	memset(str, '0', minwidth-len);
+	return str + minwidth;
 }
 
 /*
@@ -484,64 +589,10 @@ pg_ltostr_zeropad(char *str, int32 value, int32 minwidth)
  * result.
  */
 char *
-pg_ltostr(char *str, int32 value)
+pg_ultostr(char *str, uint32 value)
 {
-	char	   *start;
-	char	   *end;
-
-	/*
-	 * Handle negative numbers in a special way.  We can't just write a '-'
-	 * prefix and reverse the sign as that would overflow for INT32_MIN.
-	 */
-	if (value < 0)
-	{
-		*str++ = '-';
-
-		/* Mark the position we must reverse the string from. */
-		start = str;
-
-		/* Compute the result string backwards. */
-		do
-		{
-			int32		oldval = value;
-			int32		remainder;
-
-			value /= 10;
-			remainder = oldval - value * 10;
-			/* As above, we expect remainder to be negative. */
-			*str++ = '0' - remainder;
-		} while (value != 0);
-	}
-	else
-	{
-		/* Mark the position we must reverse the string from. */
-		start = str;
-
-		/* Compute the result string backwards. */
-		do
-		{
-			int32		oldval = value;
-			int32		remainder;
-
-			value /= 10;
-			remainder = oldval - value * 10;
-			*str++ = '0' + remainder;
-		} while (value != 0);
-	}
-
-	/* Remember the end+1 and back up 'str' to the last character. */
-	end = str--;
-
-	/* Reverse string. */
-	while (start < str)
-	{
-		char		swap = *start;
-
-		*start++ = *str;
-		*str-- = swap;
-	}
-
-	return end;
+	int		len = pg_ultoa_n(value, str);
+	return str + len;
 }
 
 /*
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index 937ddb7ef0..f5cba27db6 100644
--- a/src/include/utils/builtins.h
+++ b/src/include/utils/builtins.h
@@ -18,6 +18,8 @@
 #include "nodes/nodes.h"
 #include "utils/fmgrprotos.h"
 
+/* Sign + the most decimal digits an 8-byte number could have */
+#define MAXINT8LEN 20
 
 /* bool.c */
 extern bool parse_bool(const char *value, bool *result);
@@ -46,10 +48,12 @@ extern int32 pg_atoi(const char *s, int size, int c);
 extern int16 pg_strtoint16(const char *s);
 extern int32 pg_strtoint32(const char *s);
 extern void pg_itoa(int16 i, char *a);
+int pg_ultoa_n(uint32 l, char *a);
+int pg_ulltoa_n(uint64 l, char *a);
 extern void pg_ltoa(int32 l, char *a);
 extern void pg_lltoa(int64 ll, char *a);
-extern char *pg_ltostr_zeropad(char *str, int32 value, int32 minwidth);
-extern char *pg_ltostr(char *str, int32 value);
+extern char *pg_ultostr_zeropad(char *str, uint32 value, int32 minwidth);
+extern char *pg_ultostr(char *str, uint32 value);
 extern uint64 pg_strtouint64(const char *str, char **endptr, int base);
 
 /* oid.c */


^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH v1 1/2] Report wait event for cost-based vacuum delay
@ 2020-03-21 01:47  Justin Pryzby <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Justin Pryzby @ 2020-03-21 01:47 UTC (permalink / raw)

---
 doc/src/sgml/monitoring.sgml    | 2 ++
 src/backend/commands/vacuum.c   | 2 ++
 src/backend/postmaster/pgstat.c | 3 +++
 src/include/pgstat.h            | 3 ++-
 4 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 5bffdcce10..46c99a55b7 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -1507,6 +1507,8 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
           (<filename>pg_wal</filename>, archive or stream) before trying
           again to retrieve WAL data, at recovery.
          </entry>
+         <entry><literal>VacuumDelay</literal></entry>
+         <entry>Waiting in a cost-based vacuum delay point.</entry>
         </row>
         <row>
          <entry morerows="68"><literal>IO</literal></entry>
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index d625d17bf4..59731d687f 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -2019,7 +2019,9 @@ vacuum_delay_point(void)
 		if (msec > VacuumCostDelay * 4)
 			msec = VacuumCostDelay * 4;
 
+		pgstat_report_wait_start(WAIT_EVENT_VACUUM_DELAY);
 		pg_usleep((long) (msec * 1000));
+		pgstat_report_wait_end();
 
 		VacuumCostBalance = 0;
 
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index d29c211a76..742ec07b59 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -3824,6 +3824,9 @@ pgstat_get_wait_timeout(WaitEventTimeout w)
 		case WAIT_EVENT_RECOVERY_RETRIEVE_RETRY_INTERVAL:
 			event_name = "RecoveryRetrieveRetryInterval";
 			break;
+		case WAIT_EVENT_VACUUM_DELAY:
+			event_name = "VacuumDelay";
+			break;
 			/* no default case, so that compiler will warn */
 	}
 
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 851d0a7246..4db40e23cc 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -848,7 +848,8 @@ typedef enum
 	WAIT_EVENT_BASE_BACKUP_THROTTLE = PG_WAIT_TIMEOUT,
 	WAIT_EVENT_PG_SLEEP,
 	WAIT_EVENT_RECOVERY_APPLY_DELAY,
-	WAIT_EVENT_RECOVERY_RETRIEVE_RETRY_INTERVAL
+	WAIT_EVENT_RECOVERY_RETRIEVE_RETRY_INTERVAL,
+	WAIT_EVENT_VACUUM_DELAY,
 } WaitEventTimeout;
 
 /* ----------
-- 
2.17.0


--9jxsPFA5p3P2qPhR
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
 filename="v1-0002-vacuum-to-report-time-spent-in-cost-based-delay.patch"



^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH v4 5/6] Handle pg_get_expr default args in system_functions.sql
@ 2025-12-09 19:17  Mark Wong <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Mark Wong @ 2025-12-09 19:17 UTC (permalink / raw)

Modernize pg_get_expr to use proargdefaults to handle the optional
pretty argument.  That also means any direct function calls now needs to
set the pretty parameter.
---
 src/backend/commands/tablecmds.c  |  5 +++--
 src/backend/utils/adt/ruleutils.c | 17 -----------------
 src/include/catalog/pg_proc.dat   |  7 +++----
 3 files changed, 6 insertions(+), 23 deletions(-)

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index b04b0dbd2a0..a523a512949 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -17477,8 +17477,9 @@ decompile_conbin(HeapTuple contup, TupleDesc tupdesc)
 	if (isnull)
 		elog(ERROR, "null conbin for constraint %u", con->oid);
 
-	expr = DirectFunctionCall2(pg_get_expr, attr,
-							   ObjectIdGetDatum(con->conrelid));
+	expr = DirectFunctionCall3(pg_get_expr, attr,
+							   ObjectIdGetDatum(con->conrelid),
+							   BoolGetDatum(false));
 	return TextDatumGetCString(expr);
 }
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 03550f0d80b..a70807e84ca 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -2574,23 +2574,6 @@ decompile_column_index_array(Datum column_index_array, Oid relId,
  */
 Datum
 pg_get_expr(PG_FUNCTION_ARGS)
-{
-	text	   *expr = PG_GETARG_TEXT_PP(0);
-	Oid			relid = PG_GETARG_OID(1);
-	text	   *result;
-	int			prettyFlags;
-
-	prettyFlags = PRETTYFLAG_INDENT;
-
-	result = pg_get_expr_worker(expr, relid, prettyFlags);
-	if (result)
-		PG_RETURN_TEXT_P(result);
-	else
-		PG_RETURN_NULL();
-}
-
-Datum
-pg_get_expr_ext(PG_FUNCTION_ARGS)
 {
 	text	   *expr = PG_GETARG_TEXT_PP(0);
 	Oid			relid = PG_GETARG_OID(1);
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 1d1b24a8f4c..69c1e5bb264 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -3987,9 +3987,6 @@
 { oid => '1662', descr => 'trigger description',
   proname => 'pg_get_triggerdef', provolatile => 's', prorettype => 'text',
   proargtypes => 'oid', prosrc => 'pg_get_triggerdef' },
-{ oid => '1716', descr => 'deparse an encoded expression',
-  proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid', prosrc => 'pg_get_expr' },
 { oid => '1665', descr => 'name of sequence for a serial column',
   proname => 'pg_get_serial_sequence', provolatile => 's', prorettype => 'text',
   proargtypes => 'text text', prosrc => 'pg_get_serial_sequence' },
@@ -8531,7 +8528,9 @@
 { oid => '2509',
   descr => 'deparse an encoded expression with pretty-print option',
   proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid bool', prosrc => 'pg_get_expr_ext' },
+  proargtypes => 'pg_node_tree oid bool',
+  proargnames => '{expr,relation,pretty}', proargdefaults => '{false}',
+  prosrc => 'pg_get_expr' },
 { oid => '2510', descr => 'get the prepared statements for this session',
   proname => 'pg_prepared_statement', prorows => '1000', proretset => 't',
   provolatile => 's', proparallel => 'r', prorettype => 'record',
-- 
2.43.0


--eEEy3EHc57lA8spa
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0006-Handle-pg_get_triggerdef-default-args-in-system_f.patch"



^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH v5 5/6] Handle pg_get_expr default args in system_functions.sql
@ 2025-12-09 19:17  Mark Wong <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Mark Wong @ 2025-12-09 19:17 UTC (permalink / raw)

Modernize pg_get_expr to use proargdefaults to handle the optional
pretty argument.  That also means any direct function calls now needs to
set the pretty parameter.
---
 src/backend/commands/tablecmds.c  |  5 +++--
 src/backend/utils/adt/ruleutils.c | 17 -----------------
 src/include/catalog/pg_proc.dat   |  7 +++----
 3 files changed, 6 insertions(+), 23 deletions(-)

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 0ce2e81f9c2..fad4202b1ff 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -17694,8 +17694,9 @@ decompile_conbin(HeapTuple contup, TupleDesc tupdesc)
 	if (isnull)
 		elog(ERROR, "null conbin for constraint %u", con->oid);
 
-	expr = DirectFunctionCall2(pg_get_expr, attr,
-							   ObjectIdGetDatum(con->conrelid));
+	expr = DirectFunctionCall3(pg_get_expr, attr,
+							   ObjectIdGetDatum(con->conrelid),
+							   BoolGetDatum(false));
 	return TextDatumGetCString(expr);
 }
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 1afa2531f30..972f89eafbc 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -2932,23 +2932,6 @@ decompile_column_index_array(Datum column_index_array, Oid relId,
  */
 Datum
 pg_get_expr(PG_FUNCTION_ARGS)
-{
-	text	   *expr = PG_GETARG_TEXT_PP(0);
-	Oid			relid = PG_GETARG_OID(1);
-	text	   *result;
-	int			prettyFlags;
-
-	prettyFlags = PRETTYFLAG_INDENT;
-
-	result = pg_get_expr_worker(expr, relid, prettyFlags);
-	if (result)
-		PG_RETURN_TEXT_P(result);
-	else
-		PG_RETURN_NULL();
-}
-
-Datum
-pg_get_expr_ext(PG_FUNCTION_ARGS)
 {
 	text	   *expr = PG_GETARG_TEXT_PP(0);
 	Oid			relid = PG_GETARG_OID(1);
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index e148b1ad8e3..f36f4625e50 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -4000,9 +4000,6 @@
 { oid => '1662', descr => 'trigger description',
   proname => 'pg_get_triggerdef', provolatile => 's', prorettype => 'text',
   proargtypes => 'oid', prosrc => 'pg_get_triggerdef' },
-{ oid => '1716', descr => 'deparse an encoded expression',
-  proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid', prosrc => 'pg_get_expr' },
 { oid => '1665', descr => 'name of sequence for a serial column',
   proname => 'pg_get_serial_sequence', provolatile => 's', prorettype => 'text',
   proargtypes => 'text text', prosrc => 'pg_get_serial_sequence' },
@@ -8595,7 +8592,9 @@
 { oid => '2509',
   descr => 'deparse an encoded expression with pretty-print option',
   proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid bool', prosrc => 'pg_get_expr_ext' },
+  proargtypes => 'pg_node_tree oid bool',
+  proargnames => '{expr,relation,pretty}', proargdefaults => '{false}',
+  prosrc => 'pg_get_expr' },
 { oid => '2510', descr => 'get the prepared statements for this session',
   proname => 'pg_prepared_statement', prorows => '1000', proretset => 't',
   provolatile => 's', proparallel => 'r', prorettype => 'record',
-- 
2.52.0


--m23X5uHFNxthGTU3
Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment;
	filename=v5-0006-Handle-pg_get_triggerdef-default-args-in-system_f.patch



^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH v7 5/6] Handle pg_get_expr default args in system_functions.sql
@ 2025-12-09 19:17  Mark Wong <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Mark Wong @ 2025-12-09 19:17 UTC (permalink / raw)

Modernize pg_get_expr to use proargdefaults to handle the optional
pretty argument.  That also means any direct function calls now needs to
set the pretty parameter.
---
 src/backend/commands/tablecmds.c  |  5 +++--
 src/backend/utils/adt/ruleutils.c | 17 -----------------
 src/include/catalog/pg_proc.dat   |  9 ++++-----
 3 files changed, 7 insertions(+), 24 deletions(-)

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index eec09ba1ded..73eb6322daf 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -17695,8 +17695,9 @@ decompile_conbin(HeapTuple contup, TupleDesc tupdesc)
 	if (isnull)
 		elog(ERROR, "null conbin for constraint %u", con->oid);
 
-	expr = DirectFunctionCall2(pg_get_expr, attr,
-							   ObjectIdGetDatum(con->conrelid));
+	expr = DirectFunctionCall3(pg_get_expr, attr,
+							   ObjectIdGetDatum(con->conrelid),
+							   BoolGetDatum(false));
 	return TextDatumGetCString(expr);
 }
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 2d39bce7fd7..707f83d4310 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -2932,23 +2932,6 @@ decompile_column_index_array(Datum column_index_array, Oid relId,
  */
 Datum
 pg_get_expr(PG_FUNCTION_ARGS)
-{
-	text	   *expr = PG_GETARG_TEXT_PP(0);
-	Oid			relid = PG_GETARG_OID(1);
-	text	   *result;
-	int			prettyFlags;
-
-	prettyFlags = PRETTYFLAG_INDENT;
-
-	result = pg_get_expr_worker(expr, relid, prettyFlags);
-	if (result)
-		PG_RETURN_TEXT_P(result);
-	else
-		PG_RETURN_NULL();
-}
-
-Datum
-pg_get_expr_ext(PG_FUNCTION_ARGS)
 {
 	text	   *expr = PG_GETARG_TEXT_PP(0);
 	Oid			relid = PG_GETARG_OID(1);
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 39139fd9e3b..855529509de 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -4006,9 +4006,6 @@
 { oid => '1662', descr => 'trigger description',
   proname => 'pg_get_triggerdef', provolatile => 's', prorettype => 'text',
   proargtypes => 'oid', prosrc => 'pg_get_triggerdef' },
-{ oid => '1716', descr => 'deparse an encoded expression',
-  proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid', prosrc => 'pg_get_expr' },
 { oid => '1665', descr => 'name of sequence for a serial column',
   proname => 'pg_get_serial_sequence', provolatile => 's', prorettype => 'text',
   proargtypes => 'text text', prosrc => 'pg_get_serial_sequence' },
@@ -8638,9 +8635,11 @@
   pronargdefaults => '1', proargdefaults => '{NULL}',
   prosrc => 'pg_get_database_ddl' },
 { oid => '2509',
-  descr => 'deparse an encoded expression with pretty-print option',
+  descr => 'deparse an encoded expression',
   proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid bool', prosrc => 'pg_get_expr_ext' },
+  proargtypes => 'pg_node_tree oid bool',
+  proargnames => '{expr,relation,pretty}', proargdefaults => '{false}',
+  prosrc => 'pg_get_expr' },
 { oid => '2510', descr => 'get the prepared statements for this session',
   proname => 'pg_prepared_statement', prorows => '1000', proretset => 't',
   provolatile => 's', proparallel => 'r', prorettype => 'record',
-- 
2.52.0


--GzYugJnip6WHHvTk
Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment;
	filename=v7-0006-Handle-pg_get_triggerdef-default-args-in-system_f.patch



^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH v8 5/6] Handle pg_get_expr default args in system_functions.sql
@ 2025-12-09 19:17  Mark Wong <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Mark Wong @ 2025-12-09 19:17 UTC (permalink / raw)

Modernize pg_get_expr to use proargdefaults to handle the optional
pretty argument.  That also means any direct function calls now needs to
set the pretty parameter.
---
 src/backend/commands/tablecmds.c  |  5 +++--
 src/backend/utils/adt/ruleutils.c | 17 -----------------
 src/include/catalog/pg_proc.dat   |  9 ++++-----
 3 files changed, 7 insertions(+), 24 deletions(-)

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index a1845240a98..f063f744f6d 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -17730,8 +17730,9 @@ decompile_conbin(HeapTuple contup, TupleDesc tupdesc)
 	if (isnull)
 		elog(ERROR, "null conbin for constraint %u", con->oid);
 
-	expr = DirectFunctionCall2(pg_get_expr, attr,
-							   ObjectIdGetDatum(con->conrelid));
+	expr = DirectFunctionCall3(pg_get_expr, attr,
+							   ObjectIdGetDatum(con->conrelid),
+							   BoolGetDatum(false));
 	return TextDatumGetCString(expr);
 }
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index d83be8cf77d..e60478677e0 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -2932,23 +2932,6 @@ decompile_column_index_array(Datum column_index_array, Oid relId,
  */
 Datum
 pg_get_expr(PG_FUNCTION_ARGS)
-{
-	text	   *expr = PG_GETARG_TEXT_PP(0);
-	Oid			relid = PG_GETARG_OID(1);
-	text	   *result;
-	int			prettyFlags;
-
-	prettyFlags = PRETTYFLAG_INDENT;
-
-	result = pg_get_expr_worker(expr, relid, prettyFlags);
-	if (result)
-		PG_RETURN_TEXT_P(result);
-	else
-		PG_RETURN_NULL();
-}
-
-Datum
-pg_get_expr_ext(PG_FUNCTION_ARGS)
 {
 	text	   *expr = PG_GETARG_TEXT_PP(0);
 	Oid			relid = PG_GETARG_OID(1);
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 7e452aa8c27..71bd2aaf3d9 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -4006,9 +4006,6 @@
 { oid => '1662', descr => 'trigger description',
   proname => 'pg_get_triggerdef', provolatile => 's', prorettype => 'text',
   proargtypes => 'oid', prosrc => 'pg_get_triggerdef' },
-{ oid => '1716', descr => 'deparse an encoded expression',
-  proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid', prosrc => 'pg_get_expr' },
 { oid => '1665', descr => 'name of sequence for a serial column',
   proname => 'pg_get_serial_sequence', provolatile => 's', prorettype => 'text',
   proargtypes => 'text text', prosrc => 'pg_get_serial_sequence' },
@@ -8605,9 +8602,11 @@
   proargmodes => '{i,v}', proargdefaults => '{NULL}',
   prosrc => 'pg_get_database_ddl' },
 { oid => '2509',
-  descr => 'deparse an encoded expression with pretty-print option',
+  descr => 'deparse an encoded expression',
   proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid bool', prosrc => 'pg_get_expr_ext' },
+  proargtypes => 'pg_node_tree oid bool',
+  proargnames => '{expr,relation,pretty}', proargdefaults => '{false}',
+  prosrc => 'pg_get_expr' },
 { oid => '2510', descr => 'get the prepared statements for this session',
   proname => 'pg_prepared_statement', prorows => '1000', proretset => 't',
   provolatile => 's', proparallel => 'r', prorettype => 'record',
-- 
2.53.0


--iWwo79nqhOvOs5kf
Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment;
	filename=v8-0006-Handle-pg_get_triggerdef-default-args-in-system_f.patch



^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH v8.1 5/6] Handle pg_get_expr default args in system_functions.sql
@ 2025-12-09 19:17  Mark Wong <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Mark Wong @ 2025-12-09 19:17 UTC (permalink / raw)

Modernize pg_get_expr to use proargdefaults to handle the optional
pretty argument.  That also means any direct function calls now needs to
set the pretty parameter.
---
 src/backend/commands/tablecmds.c  |  5 +++--
 src/backend/utils/adt/ruleutils.c | 17 -----------------
 src/include/catalog/pg_proc.dat   |  9 ++++-----
 3 files changed, 7 insertions(+), 24 deletions(-)

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index a1845240a98..f063f744f6d 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -17730,8 +17730,9 @@ decompile_conbin(HeapTuple contup, TupleDesc tupdesc)
 	if (isnull)
 		elog(ERROR, "null conbin for constraint %u", con->oid);
 
-	expr = DirectFunctionCall2(pg_get_expr, attr,
-							   ObjectIdGetDatum(con->conrelid));
+	expr = DirectFunctionCall3(pg_get_expr, attr,
+							   ObjectIdGetDatum(con->conrelid),
+							   BoolGetDatum(false));
 	return TextDatumGetCString(expr);
 }
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index d83be8cf77d..e60478677e0 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -2932,23 +2932,6 @@ decompile_column_index_array(Datum column_index_array, Oid relId,
  */
 Datum
 pg_get_expr(PG_FUNCTION_ARGS)
-{
-	text	   *expr = PG_GETARG_TEXT_PP(0);
-	Oid			relid = PG_GETARG_OID(1);
-	text	   *result;
-	int			prettyFlags;
-
-	prettyFlags = PRETTYFLAG_INDENT;
-
-	result = pg_get_expr_worker(expr, relid, prettyFlags);
-	if (result)
-		PG_RETURN_TEXT_P(result);
-	else
-		PG_RETURN_NULL();
-}
-
-Datum
-pg_get_expr_ext(PG_FUNCTION_ARGS)
 {
 	text	   *expr = PG_GETARG_TEXT_PP(0);
 	Oid			relid = PG_GETARG_OID(1);
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index e610a6213ec..df43469be3d 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -4006,9 +4006,6 @@
 { oid => '1662', descr => 'trigger description',
   proname => 'pg_get_triggerdef', provolatile => 's', prorettype => 'text',
   proargtypes => 'oid', prosrc => 'pg_get_triggerdef' },
-{ oid => '1716', descr => 'deparse an encoded expression',
-  proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid', prosrc => 'pg_get_expr' },
 { oid => '1665', descr => 'name of sequence for a serial column',
   proname => 'pg_get_serial_sequence', provolatile => 's', prorettype => 'text',
   proargtypes => 'text text', prosrc => 'pg_get_serial_sequence' },
@@ -8605,9 +8602,11 @@
   proargmodes => '{i,v}', proargdefaults => '{NULL}',
   prosrc => 'pg_get_database_ddl' },
 { oid => '2509',
-  descr => 'deparse an encoded expression with pretty-print option',
+  descr => 'deparse an encoded expression',
   proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid bool', prosrc => 'pg_get_expr_ext' },
+  proargtypes => 'pg_node_tree oid bool',
+  proargnames => '{expr,relation,pretty}', proargdefaults => '{false}',
+  prosrc => 'pg_get_expr' },
 { oid => '2510', descr => 'get the prepared statements for this session',
   proname => 'pg_prepared_statement', prorows => '1000', proretset => 't',
   provolatile => 's', proparallel => 'r', prorettype => 'record',
-- 
2.53.0


--AcCatzXgbvyipyEy
Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment;
	filename=v8.1-0006-Handle-pg_get_triggerdef-default-args-in-system.patch



^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH v1 5/6] Handle pg_get_expr default args in system_functions.sql
@ 2025-12-09 19:17  Mark Wong <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Mark Wong @ 2025-12-09 19:17 UTC (permalink / raw)

Modernize pg_get_expr to use CREATE OR REPLACE FUNCTION to handle the
optional pretty argument.
---
 src/backend/catalog/system_functions.sql |  7 +++++++
 src/backend/utils/adt/ruleutils.c        | 17 -----------------
 src/include/catalog/pg_proc.dat          |  5 +----
 3 files changed, 8 insertions(+), 21 deletions(-)

diff --git a/src/backend/catalog/system_functions.sql b/src/backend/catalog/system_functions.sql
index 1f89dcc7908..81d210a9c45 100644
--- a/src/backend/catalog/system_functions.sql
+++ b/src/backend/catalog/system_functions.sql
@@ -692,6 +692,13 @@ LANGUAGE INTERNAL
 PARALLEL SAFE
 AS 'pg_get_constraintdef';
 
+CREATE OR REPLACE FUNCTION
+  pg_get_expr(expr pg_node_tree, relation oid, pretty bool DEFAULT false)
+RETURNS TEXT
+LANGUAGE INTERNAL
+PARALLEL SAFE
+AS 'pg_get_expr';
+
 --
 -- The default permissions for functions mean that anyone can execute them.
 -- A number of functions shouldn't be executable by just anyone, but rather
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 416144c49f5..9effa02fa2e 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -2573,23 +2573,6 @@ decompile_column_index_array(Datum column_index_array, Oid relId,
  */
 Datum
 pg_get_expr(PG_FUNCTION_ARGS)
-{
-	text	   *expr = PG_GETARG_TEXT_PP(0);
-	Oid			relid = PG_GETARG_OID(1);
-	text	   *result;
-	int			prettyFlags;
-
-	prettyFlags = PRETTYFLAG_INDENT;
-
-	result = pg_get_expr_worker(expr, relid, prettyFlags);
-	if (result)
-		PG_RETURN_TEXT_P(result);
-	else
-		PG_RETURN_NULL();
-}
-
-Datum
-pg_get_expr_ext(PG_FUNCTION_ARGS)
 {
 	text	   *expr = PG_GETARG_TEXT_PP(0);
 	Oid			relid = PG_GETARG_OID(1);
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index a9431ea4037..10c5286bd7d 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -3977,9 +3977,6 @@
 { oid => '1662', descr => 'trigger description',
   proname => 'pg_get_triggerdef', provolatile => 's', prorettype => 'text',
   proargtypes => 'oid', prosrc => 'pg_get_triggerdef' },
-{ oid => '1716', descr => 'deparse an encoded expression',
-  proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid', prosrc => 'pg_get_expr' },
 { oid => '1665', descr => 'name of sequence for a serial column',
   proname => 'pg_get_serial_sequence', provolatile => 's', prorettype => 'text',
   proargtypes => 'text text', prosrc => 'pg_get_serial_sequence' },
@@ -8502,7 +8499,7 @@
 { oid => '2509',
   descr => 'deparse an encoded expression with pretty-print option',
   proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid bool', prosrc => 'pg_get_expr_ext' },
+  proargtypes => 'pg_node_tree oid bool', prosrc => 'pg_get_expr' },
 { oid => '2510', descr => 'get the prepared statements for this session',
   proname => 'pg_prepared_statement', prorows => '1000', proretset => 't',
   provolatile => 's', proparallel => 'r', prorettype => 'record',
-- 
2.51.2


--IRGsBYp1UN8d6WrT
Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment;
	filename=v1-0006-Handle-pg_get_triggerdef-default-args-in-system_f.patch



^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH v2 5/6] Handle pg_get_expr default args in system_functions.sql
@ 2025-12-09 19:17  Mark Wong <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Mark Wong @ 2025-12-09 19:17 UTC (permalink / raw)

Modernize pg_get_expr to use CREATE OR REPLACE FUNCTION to handle the
optional pretty argument.
---
 src/backend/catalog/system_functions.sql |  7 +++++++
 src/backend/commands/tablecmds.c         |  4 ++--
 src/backend/utils/adt/ruleutils.c        | 17 -----------------
 src/include/catalog/pg_proc.dat          |  5 +----
 4 files changed, 10 insertions(+), 23 deletions(-)

diff --git a/src/backend/catalog/system_functions.sql b/src/backend/catalog/system_functions.sql
index 1824faab231..a6f7cdf3a36 100644
--- a/src/backend/catalog/system_functions.sql
+++ b/src/backend/catalog/system_functions.sql
@@ -692,6 +692,13 @@ LANGUAGE INTERNAL
 PARALLEL SAFE
 AS 'pg_get_constraintdef';
 
+CREATE OR REPLACE FUNCTION
+  pg_get_expr(expr pg_node_tree, relation oid, pretty bool DEFAULT false)
+RETURNS TEXT
+LANGUAGE INTERNAL
+PARALLEL SAFE
+AS 'pg_get_expr';
+
 --
 -- The default permissions for functions mean that anyone can execute them.
 -- A number of functions shouldn't be executable by just anyone, but rather
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index f976c0e5c7e..12c4ce08437 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -17480,8 +17480,8 @@ decompile_conbin(HeapTuple contup, TupleDesc tupdesc)
 	if (isnull)
 		elog(ERROR, "null conbin for constraint %u", con->oid);
 
-	expr = DirectFunctionCall2(pg_get_expr, attr,
-							   ObjectIdGetDatum(con->conrelid));
+	expr = DirectFunctionCall3(pg_get_expr, attr,
+							   ObjectIdGetDatum(con->conrelid), false);
 	return TextDatumGetCString(expr);
 }
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 9faf340f0c6..305e3e80c41 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -2573,23 +2573,6 @@ decompile_column_index_array(Datum column_index_array, Oid relId,
  */
 Datum
 pg_get_expr(PG_FUNCTION_ARGS)
-{
-	text	   *expr = PG_GETARG_TEXT_PP(0);
-	Oid			relid = PG_GETARG_OID(1);
-	text	   *result;
-	int			prettyFlags;
-
-	prettyFlags = PRETTYFLAG_INDENT;
-
-	result = pg_get_expr_worker(expr, relid, prettyFlags);
-	if (result)
-		PG_RETURN_TEXT_P(result);
-	else
-		PG_RETURN_NULL();
-}
-
-Datum
-pg_get_expr_ext(PG_FUNCTION_ARGS)
 {
 	text	   *expr = PG_GETARG_TEXT_PP(0);
 	Oid			relid = PG_GETARG_OID(1);
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 96eb7baf8e0..3a0be2d4b2a 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -3986,9 +3986,6 @@
 { oid => '1662', descr => 'trigger description',
   proname => 'pg_get_triggerdef', provolatile => 's', prorettype => 'text',
   proargtypes => 'oid', prosrc => 'pg_get_triggerdef' },
-{ oid => '1716', descr => 'deparse an encoded expression',
-  proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid', prosrc => 'pg_get_expr' },
 { oid => '1665', descr => 'name of sequence for a serial column',
   proname => 'pg_get_serial_sequence', provolatile => 's', prorettype => 'text',
   proargtypes => 'text text', prosrc => 'pg_get_serial_sequence' },
@@ -8518,7 +8515,7 @@
 { oid => '2509',
   descr => 'deparse an encoded expression with pretty-print option',
   proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid bool', prosrc => 'pg_get_expr_ext' },
+  proargtypes => 'pg_node_tree oid bool', prosrc => 'pg_get_expr' },
 { oid => '2510', descr => 'get the prepared statements for this session',
   proname => 'pg_prepared_statement', prorows => '1000', proretset => 't',
   provolatile => 's', proparallel => 'r', prorettype => 'record',
-- 
2.43.0


--3/nz5wg6+DYwHsLU
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v2-0006-Handle-pg_get_triggerdef-default-args-in-system_f.patch"



^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH v3 6/7] Handle pg_get_expr default args in system_functions.sql
@ 2025-12-09 19:17  Mark Wong <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Mark Wong @ 2025-12-09 19:17 UTC (permalink / raw)

Modernize pg_get_expr to use CREATE OR REPLACE FUNCTION to handle the
optional pretty argument.
---
 src/backend/catalog/system_functions.sql |  7 +++++++
 src/backend/commands/tablecmds.c         |  4 ++--
 src/backend/utils/adt/ruleutils.c        | 17 -----------------
 src/include/catalog/pg_proc.dat          |  5 +----
 src/include/catalog/pg_retired.dat       |  3 ++-
 5 files changed, 12 insertions(+), 24 deletions(-)

diff --git a/src/backend/catalog/system_functions.sql b/src/backend/catalog/system_functions.sql
index 1824faab231..a6f7cdf3a36 100644
--- a/src/backend/catalog/system_functions.sql
+++ b/src/backend/catalog/system_functions.sql
@@ -692,6 +692,13 @@ LANGUAGE INTERNAL
 PARALLEL SAFE
 AS 'pg_get_constraintdef';
 
+CREATE OR REPLACE FUNCTION
+  pg_get_expr(expr pg_node_tree, relation oid, pretty bool DEFAULT false)
+RETURNS TEXT
+LANGUAGE INTERNAL
+PARALLEL SAFE
+AS 'pg_get_expr';
+
 --
 -- The default permissions for functions mean that anyone can execute them.
 -- A number of functions shouldn't be executable by just anyone, but rather
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index f976c0e5c7e..12c4ce08437 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -17480,8 +17480,8 @@ decompile_conbin(HeapTuple contup, TupleDesc tupdesc)
 	if (isnull)
 		elog(ERROR, "null conbin for constraint %u", con->oid);
 
-	expr = DirectFunctionCall2(pg_get_expr, attr,
-							   ObjectIdGetDatum(con->conrelid));
+	expr = DirectFunctionCall3(pg_get_expr, attr,
+							   ObjectIdGetDatum(con->conrelid), false);
 	return TextDatumGetCString(expr);
 }
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 4f2c93f1ee2..d87b361a093 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -2573,23 +2573,6 @@ decompile_column_index_array(Datum column_index_array, Oid relId,
  */
 Datum
 pg_get_expr(PG_FUNCTION_ARGS)
-{
-	text	   *expr = PG_GETARG_TEXT_PP(0);
-	Oid			relid = PG_GETARG_OID(1);
-	text	   *result;
-	int			prettyFlags;
-
-	prettyFlags = PRETTYFLAG_INDENT;
-
-	result = pg_get_expr_worker(expr, relid, prettyFlags);
-	if (result)
-		PG_RETURN_TEXT_P(result);
-	else
-		PG_RETURN_NULL();
-}
-
-Datum
-pg_get_expr_ext(PG_FUNCTION_ARGS)
 {
 	text	   *expr = PG_GETARG_TEXT_PP(0);
 	Oid			relid = PG_GETARG_OID(1);
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index ffec11c5539..4304ab220ba 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -3986,9 +3986,6 @@
 { oid => '1662', descr => 'trigger description',
   proname => 'pg_get_triggerdef', provolatile => 's', prorettype => 'text',
   proargtypes => 'oid', prosrc => 'pg_get_triggerdef' },
-{ oid => '1716', descr => 'deparse an encoded expression',
-  proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid', prosrc => 'pg_get_expr' },
 { oid => '1665', descr => 'name of sequence for a serial column',
   proname => 'pg_get_serial_sequence', provolatile => 's', prorettype => 'text',
   proargtypes => 'text text', prosrc => 'pg_get_serial_sequence' },
@@ -8518,7 +8515,7 @@
 { oid => '2509',
   descr => 'deparse an encoded expression with pretty-print option',
   proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid bool', prosrc => 'pg_get_expr_ext' },
+  proargtypes => 'pg_node_tree oid bool', prosrc => 'pg_get_expr' },
 { oid => '2510', descr => 'get the prepared statements for this session',
   proname => 'pg_prepared_statement', prorows => '1000', proretset => 't',
   provolatile => 's', proparallel => 'r', prorettype => 'record',
diff --git a/src/include/catalog/pg_retired.dat b/src/include/catalog/pg_retired.dat
index 90928a9cb00..8b5f58850f6 100644
--- a/src/include/catalog/pg_retired.dat
+++ b/src/include/catalog/pg_retired.dat
@@ -21,6 +21,7 @@
 { oid => '1573', proname => 'pg_get_ruledef' },
 { oid => '1640', proname => 'pg_get_viewdef' },
 { oid => '1641', proname => 'pg_get_viewdef' },
-{ oid => '1643', proname => 'pg_get_indexdef' }
+{ oid => '1643', proname => 'pg_get_indexdef' },
+{ oid => '1716', proname => 'pg_get_expr' }
 
 ]
-- 
2.43.0


--zd8Z8rlPOcTi77n/
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0007-Handle-pg_get_triggerdef-default-args-in-system_f.patch"



^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH v4 5/6] Handle pg_get_expr default args in system_functions.sql
@ 2025-12-09 19:17  Mark Wong <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Mark Wong @ 2025-12-09 19:17 UTC (permalink / raw)

Modernize pg_get_expr to use proargdefaults to handle the optional
pretty argument.  That also means any direct function calls now needs to
set the pretty parameter.
---
 src/backend/commands/tablecmds.c  |  5 +++--
 src/backend/utils/adt/ruleutils.c | 17 -----------------
 src/include/catalog/pg_proc.dat   |  7 +++----
 3 files changed, 6 insertions(+), 23 deletions(-)

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index b04b0dbd2a0..a523a512949 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -17477,8 +17477,9 @@ decompile_conbin(HeapTuple contup, TupleDesc tupdesc)
 	if (isnull)
 		elog(ERROR, "null conbin for constraint %u", con->oid);
 
-	expr = DirectFunctionCall2(pg_get_expr, attr,
-							   ObjectIdGetDatum(con->conrelid));
+	expr = DirectFunctionCall3(pg_get_expr, attr,
+							   ObjectIdGetDatum(con->conrelid),
+							   BoolGetDatum(false));
 	return TextDatumGetCString(expr);
 }
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 03550f0d80b..a70807e84ca 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -2574,23 +2574,6 @@ decompile_column_index_array(Datum column_index_array, Oid relId,
  */
 Datum
 pg_get_expr(PG_FUNCTION_ARGS)
-{
-	text	   *expr = PG_GETARG_TEXT_PP(0);
-	Oid			relid = PG_GETARG_OID(1);
-	text	   *result;
-	int			prettyFlags;
-
-	prettyFlags = PRETTYFLAG_INDENT;
-
-	result = pg_get_expr_worker(expr, relid, prettyFlags);
-	if (result)
-		PG_RETURN_TEXT_P(result);
-	else
-		PG_RETURN_NULL();
-}
-
-Datum
-pg_get_expr_ext(PG_FUNCTION_ARGS)
 {
 	text	   *expr = PG_GETARG_TEXT_PP(0);
 	Oid			relid = PG_GETARG_OID(1);
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 1d1b24a8f4c..69c1e5bb264 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -3987,9 +3987,6 @@
 { oid => '1662', descr => 'trigger description',
   proname => 'pg_get_triggerdef', provolatile => 's', prorettype => 'text',
   proargtypes => 'oid', prosrc => 'pg_get_triggerdef' },
-{ oid => '1716', descr => 'deparse an encoded expression',
-  proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid', prosrc => 'pg_get_expr' },
 { oid => '1665', descr => 'name of sequence for a serial column',
   proname => 'pg_get_serial_sequence', provolatile => 's', prorettype => 'text',
   proargtypes => 'text text', prosrc => 'pg_get_serial_sequence' },
@@ -8531,7 +8528,9 @@
 { oid => '2509',
   descr => 'deparse an encoded expression with pretty-print option',
   proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid bool', prosrc => 'pg_get_expr_ext' },
+  proargtypes => 'pg_node_tree oid bool',
+  proargnames => '{expr,relation,pretty}', proargdefaults => '{false}',
+  prosrc => 'pg_get_expr' },
 { oid => '2510', descr => 'get the prepared statements for this session',
   proname => 'pg_prepared_statement', prorows => '1000', proretset => 't',
   provolatile => 's', proparallel => 'r', prorettype => 'record',
-- 
2.43.0


--eEEy3EHc57lA8spa
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0006-Handle-pg_get_triggerdef-default-args-in-system_f.patch"



^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH v5 5/6] Handle pg_get_expr default args in system_functions.sql
@ 2025-12-09 19:17  Mark Wong <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Mark Wong @ 2025-12-09 19:17 UTC (permalink / raw)

Modernize pg_get_expr to use proargdefaults to handle the optional
pretty argument.  That also means any direct function calls now needs to
set the pretty parameter.
---
 src/backend/commands/tablecmds.c  |  5 +++--
 src/backend/utils/adt/ruleutils.c | 17 -----------------
 src/include/catalog/pg_proc.dat   |  7 +++----
 3 files changed, 6 insertions(+), 23 deletions(-)

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 0ce2e81f9c2..fad4202b1ff 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -17694,8 +17694,9 @@ decompile_conbin(HeapTuple contup, TupleDesc tupdesc)
 	if (isnull)
 		elog(ERROR, "null conbin for constraint %u", con->oid);
 
-	expr = DirectFunctionCall2(pg_get_expr, attr,
-							   ObjectIdGetDatum(con->conrelid));
+	expr = DirectFunctionCall3(pg_get_expr, attr,
+							   ObjectIdGetDatum(con->conrelid),
+							   BoolGetDatum(false));
 	return TextDatumGetCString(expr);
 }
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 1afa2531f30..972f89eafbc 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -2932,23 +2932,6 @@ decompile_column_index_array(Datum column_index_array, Oid relId,
  */
 Datum
 pg_get_expr(PG_FUNCTION_ARGS)
-{
-	text	   *expr = PG_GETARG_TEXT_PP(0);
-	Oid			relid = PG_GETARG_OID(1);
-	text	   *result;
-	int			prettyFlags;
-
-	prettyFlags = PRETTYFLAG_INDENT;
-
-	result = pg_get_expr_worker(expr, relid, prettyFlags);
-	if (result)
-		PG_RETURN_TEXT_P(result);
-	else
-		PG_RETURN_NULL();
-}
-
-Datum
-pg_get_expr_ext(PG_FUNCTION_ARGS)
 {
 	text	   *expr = PG_GETARG_TEXT_PP(0);
 	Oid			relid = PG_GETARG_OID(1);
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index e148b1ad8e3..f36f4625e50 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -4000,9 +4000,6 @@
 { oid => '1662', descr => 'trigger description',
   proname => 'pg_get_triggerdef', provolatile => 's', prorettype => 'text',
   proargtypes => 'oid', prosrc => 'pg_get_triggerdef' },
-{ oid => '1716', descr => 'deparse an encoded expression',
-  proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid', prosrc => 'pg_get_expr' },
 { oid => '1665', descr => 'name of sequence for a serial column',
   proname => 'pg_get_serial_sequence', provolatile => 's', prorettype => 'text',
   proargtypes => 'text text', prosrc => 'pg_get_serial_sequence' },
@@ -8595,7 +8592,9 @@
 { oid => '2509',
   descr => 'deparse an encoded expression with pretty-print option',
   proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid bool', prosrc => 'pg_get_expr_ext' },
+  proargtypes => 'pg_node_tree oid bool',
+  proargnames => '{expr,relation,pretty}', proargdefaults => '{false}',
+  prosrc => 'pg_get_expr' },
 { oid => '2510', descr => 'get the prepared statements for this session',
   proname => 'pg_prepared_statement', prorows => '1000', proretset => 't',
   provolatile => 's', proparallel => 'r', prorettype => 'record',
-- 
2.52.0


--m23X5uHFNxthGTU3
Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment;
	filename=v5-0006-Handle-pg_get_triggerdef-default-args-in-system_f.patch



^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH v7 5/6] Handle pg_get_expr default args in system_functions.sql
@ 2025-12-09 19:17  Mark Wong <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Mark Wong @ 2025-12-09 19:17 UTC (permalink / raw)

Modernize pg_get_expr to use proargdefaults to handle the optional
pretty argument.  That also means any direct function calls now needs to
set the pretty parameter.
---
 src/backend/commands/tablecmds.c  |  5 +++--
 src/backend/utils/adt/ruleutils.c | 17 -----------------
 src/include/catalog/pg_proc.dat   |  9 ++++-----
 3 files changed, 7 insertions(+), 24 deletions(-)

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index eec09ba1ded..73eb6322daf 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -17695,8 +17695,9 @@ decompile_conbin(HeapTuple contup, TupleDesc tupdesc)
 	if (isnull)
 		elog(ERROR, "null conbin for constraint %u", con->oid);
 
-	expr = DirectFunctionCall2(pg_get_expr, attr,
-							   ObjectIdGetDatum(con->conrelid));
+	expr = DirectFunctionCall3(pg_get_expr, attr,
+							   ObjectIdGetDatum(con->conrelid),
+							   BoolGetDatum(false));
 	return TextDatumGetCString(expr);
 }
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 2d39bce7fd7..707f83d4310 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -2932,23 +2932,6 @@ decompile_column_index_array(Datum column_index_array, Oid relId,
  */
 Datum
 pg_get_expr(PG_FUNCTION_ARGS)
-{
-	text	   *expr = PG_GETARG_TEXT_PP(0);
-	Oid			relid = PG_GETARG_OID(1);
-	text	   *result;
-	int			prettyFlags;
-
-	prettyFlags = PRETTYFLAG_INDENT;
-
-	result = pg_get_expr_worker(expr, relid, prettyFlags);
-	if (result)
-		PG_RETURN_TEXT_P(result);
-	else
-		PG_RETURN_NULL();
-}
-
-Datum
-pg_get_expr_ext(PG_FUNCTION_ARGS)
 {
 	text	   *expr = PG_GETARG_TEXT_PP(0);
 	Oid			relid = PG_GETARG_OID(1);
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 39139fd9e3b..855529509de 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -4006,9 +4006,6 @@
 { oid => '1662', descr => 'trigger description',
   proname => 'pg_get_triggerdef', provolatile => 's', prorettype => 'text',
   proargtypes => 'oid', prosrc => 'pg_get_triggerdef' },
-{ oid => '1716', descr => 'deparse an encoded expression',
-  proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid', prosrc => 'pg_get_expr' },
 { oid => '1665', descr => 'name of sequence for a serial column',
   proname => 'pg_get_serial_sequence', provolatile => 's', prorettype => 'text',
   proargtypes => 'text text', prosrc => 'pg_get_serial_sequence' },
@@ -8638,9 +8635,11 @@
   pronargdefaults => '1', proargdefaults => '{NULL}',
   prosrc => 'pg_get_database_ddl' },
 { oid => '2509',
-  descr => 'deparse an encoded expression with pretty-print option',
+  descr => 'deparse an encoded expression',
   proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid bool', prosrc => 'pg_get_expr_ext' },
+  proargtypes => 'pg_node_tree oid bool',
+  proargnames => '{expr,relation,pretty}', proargdefaults => '{false}',
+  prosrc => 'pg_get_expr' },
 { oid => '2510', descr => 'get the prepared statements for this session',
   proname => 'pg_prepared_statement', prorows => '1000', proretset => 't',
   provolatile => 's', proparallel => 'r', prorettype => 'record',
-- 
2.52.0


--GzYugJnip6WHHvTk
Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment;
	filename=v7-0006-Handle-pg_get_triggerdef-default-args-in-system_f.patch



^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH v8 5/6] Handle pg_get_expr default args in system_functions.sql
@ 2025-12-09 19:17  Mark Wong <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Mark Wong @ 2025-12-09 19:17 UTC (permalink / raw)

Modernize pg_get_expr to use proargdefaults to handle the optional
pretty argument.  That also means any direct function calls now needs to
set the pretty parameter.
---
 src/backend/commands/tablecmds.c  |  5 +++--
 src/backend/utils/adt/ruleutils.c | 17 -----------------
 src/include/catalog/pg_proc.dat   |  9 ++++-----
 3 files changed, 7 insertions(+), 24 deletions(-)

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index a1845240a98..f063f744f6d 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -17730,8 +17730,9 @@ decompile_conbin(HeapTuple contup, TupleDesc tupdesc)
 	if (isnull)
 		elog(ERROR, "null conbin for constraint %u", con->oid);
 
-	expr = DirectFunctionCall2(pg_get_expr, attr,
-							   ObjectIdGetDatum(con->conrelid));
+	expr = DirectFunctionCall3(pg_get_expr, attr,
+							   ObjectIdGetDatum(con->conrelid),
+							   BoolGetDatum(false));
 	return TextDatumGetCString(expr);
 }
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index d83be8cf77d..e60478677e0 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -2932,23 +2932,6 @@ decompile_column_index_array(Datum column_index_array, Oid relId,
  */
 Datum
 pg_get_expr(PG_FUNCTION_ARGS)
-{
-	text	   *expr = PG_GETARG_TEXT_PP(0);
-	Oid			relid = PG_GETARG_OID(1);
-	text	   *result;
-	int			prettyFlags;
-
-	prettyFlags = PRETTYFLAG_INDENT;
-
-	result = pg_get_expr_worker(expr, relid, prettyFlags);
-	if (result)
-		PG_RETURN_TEXT_P(result);
-	else
-		PG_RETURN_NULL();
-}
-
-Datum
-pg_get_expr_ext(PG_FUNCTION_ARGS)
 {
 	text	   *expr = PG_GETARG_TEXT_PP(0);
 	Oid			relid = PG_GETARG_OID(1);
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 7e452aa8c27..71bd2aaf3d9 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -4006,9 +4006,6 @@
 { oid => '1662', descr => 'trigger description',
   proname => 'pg_get_triggerdef', provolatile => 's', prorettype => 'text',
   proargtypes => 'oid', prosrc => 'pg_get_triggerdef' },
-{ oid => '1716', descr => 'deparse an encoded expression',
-  proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid', prosrc => 'pg_get_expr' },
 { oid => '1665', descr => 'name of sequence for a serial column',
   proname => 'pg_get_serial_sequence', provolatile => 's', prorettype => 'text',
   proargtypes => 'text text', prosrc => 'pg_get_serial_sequence' },
@@ -8605,9 +8602,11 @@
   proargmodes => '{i,v}', proargdefaults => '{NULL}',
   prosrc => 'pg_get_database_ddl' },
 { oid => '2509',
-  descr => 'deparse an encoded expression with pretty-print option',
+  descr => 'deparse an encoded expression',
   proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid bool', prosrc => 'pg_get_expr_ext' },
+  proargtypes => 'pg_node_tree oid bool',
+  proargnames => '{expr,relation,pretty}', proargdefaults => '{false}',
+  prosrc => 'pg_get_expr' },
 { oid => '2510', descr => 'get the prepared statements for this session',
   proname => 'pg_prepared_statement', prorows => '1000', proretset => 't',
   provolatile => 's', proparallel => 'r', prorettype => 'record',
-- 
2.53.0


--iWwo79nqhOvOs5kf
Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment;
	filename=v8-0006-Handle-pg_get_triggerdef-default-args-in-system_f.patch



^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH v8.1 5/6] Handle pg_get_expr default args in system_functions.sql
@ 2025-12-09 19:17  Mark Wong <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Mark Wong @ 2025-12-09 19:17 UTC (permalink / raw)

Modernize pg_get_expr to use proargdefaults to handle the optional
pretty argument.  That also means any direct function calls now needs to
set the pretty parameter.
---
 src/backend/commands/tablecmds.c  |  5 +++--
 src/backend/utils/adt/ruleutils.c | 17 -----------------
 src/include/catalog/pg_proc.dat   |  9 ++++-----
 3 files changed, 7 insertions(+), 24 deletions(-)

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index a1845240a98..f063f744f6d 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -17730,8 +17730,9 @@ decompile_conbin(HeapTuple contup, TupleDesc tupdesc)
 	if (isnull)
 		elog(ERROR, "null conbin for constraint %u", con->oid);
 
-	expr = DirectFunctionCall2(pg_get_expr, attr,
-							   ObjectIdGetDatum(con->conrelid));
+	expr = DirectFunctionCall3(pg_get_expr, attr,
+							   ObjectIdGetDatum(con->conrelid),
+							   BoolGetDatum(false));
 	return TextDatumGetCString(expr);
 }
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index d83be8cf77d..e60478677e0 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -2932,23 +2932,6 @@ decompile_column_index_array(Datum column_index_array, Oid relId,
  */
 Datum
 pg_get_expr(PG_FUNCTION_ARGS)
-{
-	text	   *expr = PG_GETARG_TEXT_PP(0);
-	Oid			relid = PG_GETARG_OID(1);
-	text	   *result;
-	int			prettyFlags;
-
-	prettyFlags = PRETTYFLAG_INDENT;
-
-	result = pg_get_expr_worker(expr, relid, prettyFlags);
-	if (result)
-		PG_RETURN_TEXT_P(result);
-	else
-		PG_RETURN_NULL();
-}
-
-Datum
-pg_get_expr_ext(PG_FUNCTION_ARGS)
 {
 	text	   *expr = PG_GETARG_TEXT_PP(0);
 	Oid			relid = PG_GETARG_OID(1);
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index e610a6213ec..df43469be3d 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -4006,9 +4006,6 @@
 { oid => '1662', descr => 'trigger description',
   proname => 'pg_get_triggerdef', provolatile => 's', prorettype => 'text',
   proargtypes => 'oid', prosrc => 'pg_get_triggerdef' },
-{ oid => '1716', descr => 'deparse an encoded expression',
-  proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid', prosrc => 'pg_get_expr' },
 { oid => '1665', descr => 'name of sequence for a serial column',
   proname => 'pg_get_serial_sequence', provolatile => 's', prorettype => 'text',
   proargtypes => 'text text', prosrc => 'pg_get_serial_sequence' },
@@ -8605,9 +8602,11 @@
   proargmodes => '{i,v}', proargdefaults => '{NULL}',
   prosrc => 'pg_get_database_ddl' },
 { oid => '2509',
-  descr => 'deparse an encoded expression with pretty-print option',
+  descr => 'deparse an encoded expression',
   proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid bool', prosrc => 'pg_get_expr_ext' },
+  proargtypes => 'pg_node_tree oid bool',
+  proargnames => '{expr,relation,pretty}', proargdefaults => '{false}',
+  prosrc => 'pg_get_expr' },
 { oid => '2510', descr => 'get the prepared statements for this session',
   proname => 'pg_prepared_statement', prorows => '1000', proretset => 't',
   provolatile => 's', proparallel => 'r', prorettype => 'record',
-- 
2.53.0


--AcCatzXgbvyipyEy
Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment;
	filename=v8.1-0006-Handle-pg_get_triggerdef-default-args-in-system.patch



^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH v2 5/6] Handle pg_get_expr default args in system_functions.sql
@ 2025-12-09 19:17  Mark Wong <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Mark Wong @ 2025-12-09 19:17 UTC (permalink / raw)

Modernize pg_get_expr to use CREATE OR REPLACE FUNCTION to handle the
optional pretty argument.
---
 src/backend/catalog/system_functions.sql |  7 +++++++
 src/backend/commands/tablecmds.c         |  4 ++--
 src/backend/utils/adt/ruleutils.c        | 17 -----------------
 src/include/catalog/pg_proc.dat          |  5 +----
 4 files changed, 10 insertions(+), 23 deletions(-)

diff --git a/src/backend/catalog/system_functions.sql b/src/backend/catalog/system_functions.sql
index 1824faab231..a6f7cdf3a36 100644
--- a/src/backend/catalog/system_functions.sql
+++ b/src/backend/catalog/system_functions.sql
@@ -692,6 +692,13 @@ LANGUAGE INTERNAL
 PARALLEL SAFE
 AS 'pg_get_constraintdef';
 
+CREATE OR REPLACE FUNCTION
+  pg_get_expr(expr pg_node_tree, relation oid, pretty bool DEFAULT false)
+RETURNS TEXT
+LANGUAGE INTERNAL
+PARALLEL SAFE
+AS 'pg_get_expr';
+
 --
 -- The default permissions for functions mean that anyone can execute them.
 -- A number of functions shouldn't be executable by just anyone, but rather
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index f976c0e5c7e..12c4ce08437 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -17480,8 +17480,8 @@ decompile_conbin(HeapTuple contup, TupleDesc tupdesc)
 	if (isnull)
 		elog(ERROR, "null conbin for constraint %u", con->oid);
 
-	expr = DirectFunctionCall2(pg_get_expr, attr,
-							   ObjectIdGetDatum(con->conrelid));
+	expr = DirectFunctionCall3(pg_get_expr, attr,
+							   ObjectIdGetDatum(con->conrelid), false);
 	return TextDatumGetCString(expr);
 }
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 9faf340f0c6..305e3e80c41 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -2573,23 +2573,6 @@ decompile_column_index_array(Datum column_index_array, Oid relId,
  */
 Datum
 pg_get_expr(PG_FUNCTION_ARGS)
-{
-	text	   *expr = PG_GETARG_TEXT_PP(0);
-	Oid			relid = PG_GETARG_OID(1);
-	text	   *result;
-	int			prettyFlags;
-
-	prettyFlags = PRETTYFLAG_INDENT;
-
-	result = pg_get_expr_worker(expr, relid, prettyFlags);
-	if (result)
-		PG_RETURN_TEXT_P(result);
-	else
-		PG_RETURN_NULL();
-}
-
-Datum
-pg_get_expr_ext(PG_FUNCTION_ARGS)
 {
 	text	   *expr = PG_GETARG_TEXT_PP(0);
 	Oid			relid = PG_GETARG_OID(1);
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 96eb7baf8e0..3a0be2d4b2a 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -3986,9 +3986,6 @@
 { oid => '1662', descr => 'trigger description',
   proname => 'pg_get_triggerdef', provolatile => 's', prorettype => 'text',
   proargtypes => 'oid', prosrc => 'pg_get_triggerdef' },
-{ oid => '1716', descr => 'deparse an encoded expression',
-  proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid', prosrc => 'pg_get_expr' },
 { oid => '1665', descr => 'name of sequence for a serial column',
   proname => 'pg_get_serial_sequence', provolatile => 's', prorettype => 'text',
   proargtypes => 'text text', prosrc => 'pg_get_serial_sequence' },
@@ -8518,7 +8515,7 @@
 { oid => '2509',
   descr => 'deparse an encoded expression with pretty-print option',
   proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid bool', prosrc => 'pg_get_expr_ext' },
+  proargtypes => 'pg_node_tree oid bool', prosrc => 'pg_get_expr' },
 { oid => '2510', descr => 'get the prepared statements for this session',
   proname => 'pg_prepared_statement', prorows => '1000', proretset => 't',
   provolatile => 's', proparallel => 'r', prorettype => 'record',
-- 
2.43.0


--3/nz5wg6+DYwHsLU
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v2-0006-Handle-pg_get_triggerdef-default-args-in-system_f.patch"



^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH v1 5/6] Handle pg_get_expr default args in system_functions.sql
@ 2025-12-09 19:17  Mark Wong <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Mark Wong @ 2025-12-09 19:17 UTC (permalink / raw)

Modernize pg_get_expr to use CREATE OR REPLACE FUNCTION to handle the
optional pretty argument.
---
 src/backend/catalog/system_functions.sql |  7 +++++++
 src/backend/utils/adt/ruleutils.c        | 17 -----------------
 src/include/catalog/pg_proc.dat          |  5 +----
 3 files changed, 8 insertions(+), 21 deletions(-)

diff --git a/src/backend/catalog/system_functions.sql b/src/backend/catalog/system_functions.sql
index 1f89dcc7908..81d210a9c45 100644
--- a/src/backend/catalog/system_functions.sql
+++ b/src/backend/catalog/system_functions.sql
@@ -692,6 +692,13 @@ LANGUAGE INTERNAL
 PARALLEL SAFE
 AS 'pg_get_constraintdef';
 
+CREATE OR REPLACE FUNCTION
+  pg_get_expr(expr pg_node_tree, relation oid, pretty bool DEFAULT false)
+RETURNS TEXT
+LANGUAGE INTERNAL
+PARALLEL SAFE
+AS 'pg_get_expr';
+
 --
 -- The default permissions for functions mean that anyone can execute them.
 -- A number of functions shouldn't be executable by just anyone, but rather
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 416144c49f5..9effa02fa2e 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -2573,23 +2573,6 @@ decompile_column_index_array(Datum column_index_array, Oid relId,
  */
 Datum
 pg_get_expr(PG_FUNCTION_ARGS)
-{
-	text	   *expr = PG_GETARG_TEXT_PP(0);
-	Oid			relid = PG_GETARG_OID(1);
-	text	   *result;
-	int			prettyFlags;
-
-	prettyFlags = PRETTYFLAG_INDENT;
-
-	result = pg_get_expr_worker(expr, relid, prettyFlags);
-	if (result)
-		PG_RETURN_TEXT_P(result);
-	else
-		PG_RETURN_NULL();
-}
-
-Datum
-pg_get_expr_ext(PG_FUNCTION_ARGS)
 {
 	text	   *expr = PG_GETARG_TEXT_PP(0);
 	Oid			relid = PG_GETARG_OID(1);
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index a9431ea4037..10c5286bd7d 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -3977,9 +3977,6 @@
 { oid => '1662', descr => 'trigger description',
   proname => 'pg_get_triggerdef', provolatile => 's', prorettype => 'text',
   proargtypes => 'oid', prosrc => 'pg_get_triggerdef' },
-{ oid => '1716', descr => 'deparse an encoded expression',
-  proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid', prosrc => 'pg_get_expr' },
 { oid => '1665', descr => 'name of sequence for a serial column',
   proname => 'pg_get_serial_sequence', provolatile => 's', prorettype => 'text',
   proargtypes => 'text text', prosrc => 'pg_get_serial_sequence' },
@@ -8502,7 +8499,7 @@
 { oid => '2509',
   descr => 'deparse an encoded expression with pretty-print option',
   proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid bool', prosrc => 'pg_get_expr_ext' },
+  proargtypes => 'pg_node_tree oid bool', prosrc => 'pg_get_expr' },
 { oid => '2510', descr => 'get the prepared statements for this session',
   proname => 'pg_prepared_statement', prorows => '1000', proretset => 't',
   provolatile => 's', proparallel => 'r', prorettype => 'record',
-- 
2.51.2


--IRGsBYp1UN8d6WrT
Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment;
	filename=v1-0006-Handle-pg_get_triggerdef-default-args-in-system_f.patch



^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH v3 6/7] Handle pg_get_expr default args in system_functions.sql
@ 2025-12-09 19:17  Mark Wong <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Mark Wong @ 2025-12-09 19:17 UTC (permalink / raw)

Modernize pg_get_expr to use CREATE OR REPLACE FUNCTION to handle the
optional pretty argument.
---
 src/backend/catalog/system_functions.sql |  7 +++++++
 src/backend/commands/tablecmds.c         |  4 ++--
 src/backend/utils/adt/ruleutils.c        | 17 -----------------
 src/include/catalog/pg_proc.dat          |  5 +----
 src/include/catalog/pg_retired.dat       |  3 ++-
 5 files changed, 12 insertions(+), 24 deletions(-)

diff --git a/src/backend/catalog/system_functions.sql b/src/backend/catalog/system_functions.sql
index 1824faab231..a6f7cdf3a36 100644
--- a/src/backend/catalog/system_functions.sql
+++ b/src/backend/catalog/system_functions.sql
@@ -692,6 +692,13 @@ LANGUAGE INTERNAL
 PARALLEL SAFE
 AS 'pg_get_constraintdef';
 
+CREATE OR REPLACE FUNCTION
+  pg_get_expr(expr pg_node_tree, relation oid, pretty bool DEFAULT false)
+RETURNS TEXT
+LANGUAGE INTERNAL
+PARALLEL SAFE
+AS 'pg_get_expr';
+
 --
 -- The default permissions for functions mean that anyone can execute them.
 -- A number of functions shouldn't be executable by just anyone, but rather
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index f976c0e5c7e..12c4ce08437 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -17480,8 +17480,8 @@ decompile_conbin(HeapTuple contup, TupleDesc tupdesc)
 	if (isnull)
 		elog(ERROR, "null conbin for constraint %u", con->oid);
 
-	expr = DirectFunctionCall2(pg_get_expr, attr,
-							   ObjectIdGetDatum(con->conrelid));
+	expr = DirectFunctionCall3(pg_get_expr, attr,
+							   ObjectIdGetDatum(con->conrelid), false);
 	return TextDatumGetCString(expr);
 }
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 4f2c93f1ee2..d87b361a093 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -2573,23 +2573,6 @@ decompile_column_index_array(Datum column_index_array, Oid relId,
  */
 Datum
 pg_get_expr(PG_FUNCTION_ARGS)
-{
-	text	   *expr = PG_GETARG_TEXT_PP(0);
-	Oid			relid = PG_GETARG_OID(1);
-	text	   *result;
-	int			prettyFlags;
-
-	prettyFlags = PRETTYFLAG_INDENT;
-
-	result = pg_get_expr_worker(expr, relid, prettyFlags);
-	if (result)
-		PG_RETURN_TEXT_P(result);
-	else
-		PG_RETURN_NULL();
-}
-
-Datum
-pg_get_expr_ext(PG_FUNCTION_ARGS)
 {
 	text	   *expr = PG_GETARG_TEXT_PP(0);
 	Oid			relid = PG_GETARG_OID(1);
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index ffec11c5539..4304ab220ba 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -3986,9 +3986,6 @@
 { oid => '1662', descr => 'trigger description',
   proname => 'pg_get_triggerdef', provolatile => 's', prorettype => 'text',
   proargtypes => 'oid', prosrc => 'pg_get_triggerdef' },
-{ oid => '1716', descr => 'deparse an encoded expression',
-  proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid', prosrc => 'pg_get_expr' },
 { oid => '1665', descr => 'name of sequence for a serial column',
   proname => 'pg_get_serial_sequence', provolatile => 's', prorettype => 'text',
   proargtypes => 'text text', prosrc => 'pg_get_serial_sequence' },
@@ -8518,7 +8515,7 @@
 { oid => '2509',
   descr => 'deparse an encoded expression with pretty-print option',
   proname => 'pg_get_expr', provolatile => 's', prorettype => 'text',
-  proargtypes => 'pg_node_tree oid bool', prosrc => 'pg_get_expr_ext' },
+  proargtypes => 'pg_node_tree oid bool', prosrc => 'pg_get_expr' },
 { oid => '2510', descr => 'get the prepared statements for this session',
   proname => 'pg_prepared_statement', prorows => '1000', proretset => 't',
   provolatile => 's', proparallel => 'r', prorettype => 'record',
diff --git a/src/include/catalog/pg_retired.dat b/src/include/catalog/pg_retired.dat
index 90928a9cb00..8b5f58850f6 100644
--- a/src/include/catalog/pg_retired.dat
+++ b/src/include/catalog/pg_retired.dat
@@ -21,6 +21,7 @@
 { oid => '1573', proname => 'pg_get_ruledef' },
 { oid => '1640', proname => 'pg_get_viewdef' },
 { oid => '1641', proname => 'pg_get_viewdef' },
-{ oid => '1643', proname => 'pg_get_indexdef' }
+{ oid => '1643', proname => 'pg_get_indexdef' },
+{ oid => '1716', proname => 'pg_get_expr' }
 
 ]
-- 
2.43.0


--zd8Z8rlPOcTi77n/
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0007-Handle-pg_get_triggerdef-default-args-in-system_f.patch"



^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





^ permalink  raw  reply  [nested|flat] 94+ messages in thread

* [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix.
@ 2026-05-12 10:27  Antonin Houska <[email protected]>
  0 siblings, 0 replies; 94+ messages in thread

From: Antonin Houska @ 2026-05-12 10:27 UTC (permalink / raw)

The fix: https://www.postgresql.org/message-id/77611.1778055944%40localhost
---
 src/backend/access/transam/xact.c             |   2 +
 src/backend/commands/repack_worker.c          |   2 +
 src/test/isolation/isolationtester.c          |   9 +-
 .../expected/repack_running_xacts.out         |  81 ++++++++++++
 .../specs/repack_running_xacts.spec           | 119 ++++++++++++++++++
 5 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/injection_points/expected/repack_running_xacts.out
 create mode 100644 src/test/modules/injection_points/specs/repack_running_xacts.spec

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5586fbe5b07..b63ee166028 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -65,6 +65,7 @@
 #include "utils/builtins.h"
 #include "utils/combocid.h"
 #include "utils/guc.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 #include "utils/relmapper.h"
@@ -2428,6 +2429,7 @@ CommitTransaction(void)
 	 * must be done _before_ releasing locks we hold and _after_
 	 * RecordTransactionCommit.
 	 */
+	INJECTION_POINT("before-end-transaction", NULL);
 	ProcArrayEndTransaction(MyProc, latestXid);
 
 	/*
diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c
index c40f8c98e06..6835626d677 100644
--- a/src/backend/commands/repack_worker.c
+++ b/src/backend/commands/repack_worker.c
@@ -26,6 +26,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/injection_point.h"
 #include "utils/memutils.h"
 
 #define REPL_PLUGIN_NAME   "pgrepack"
@@ -233,6 +234,7 @@ repack_setup_logical_decoding(Oid relid)
 	 * Neither prepare_write nor do_write callback nor update_progress is
 	 * useful for us.
 	 */
+	INJECTION_POINT("before-create-decoding-context", NULL);
 	ctx = CreateInitDecodingContext(REPL_PLUGIN_NAME,
 									NIL,
 									true,
diff --git a/src/test/isolation/isolationtester.c b/src/test/isolation/isolationtester.c
index 440c875b8ac..8f17ee412c9 100644
--- a/src/test/isolation/isolationtester.c
+++ b/src/test/isolation/isolationtester.c
@@ -216,15 +216,22 @@ main(int argc, char **argv)
 	 * exactly expect concurrent use of test tables.  However, autovacuum will
 	 * occasionally take AccessExclusiveLock to truncate a table, and we must
 	 * ignore that transient wait.
+	 *
+	 * If the session's backend is blocked, and if its background worker is
+	 * waiting on an injection point, we assume that the injection point is
+	 * the reason for the backend to be blocked. That's what we check in the
+	 * second query of the UNION. XXX Should we use a separate query for that?
 	 */
 	initPQExpBuffer(&wait_query);
 	appendPQExpBufferStr(&wait_query,
+						 "WITH blocking(res) AS ("
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
 	appendPQExpBufferStr(&wait_query, conns[1].backend_pid_str);
 	for (i = 2; i < nconns; i++)
 		appendPQExpBuffer(&wait_query, ",%s", conns[i].backend_pid_str);
-	appendPQExpBufferStr(&wait_query, "}')");
+	appendPQExpBufferStr(&wait_query, "}') UNION "
+						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked(pid, '{}') FROM pg_stat_activity WHERE leader_pid=$1) SELECT bool_or(res) FROM blocking");
 
 	res = PQprepare(conns[0].conn, PREP_WAITING, wait_query.data, 0, NULL);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
diff --git a/src/test/modules/injection_points/expected/repack_running_xacts.out b/src/test/modules/injection_points/expected/repack_running_xacts.out
new file mode 100644
index 00000000000..271fe2b97cb
--- /dev/null
+++ b/src/test/modules/injection_points/expected/repack_running_xacts.out
@@ -0,0 +1,81 @@
+Parsed test spec with 5 sessions
+
+starting permutation: repack s3_assign_xid wakeup_bcdc s4_changes s4_attach s4_commit s3_commit s5_assign_xid wakeup_bet s5_commit check
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step repack: 
+	REPACK (CONCURRENTLY) repack_test;
+ <waiting ...>
+step s3_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+
+step wakeup_bcdc: 
+	SELECT injection_points_wakeup('before-create-decoding-context');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step s4_changes: 
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+
+step s4_attach: 
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+
+injection_points_set_local
+--------------------------
+                          
+(1 row)
+
+injection_points_attach
+-----------------------
+                       
+(1 row)
+
+step s4_commit: 
+	COMMIT;
+ <waiting ...>
+step s3_commit: 
+	COMMIT;
+
+step s5_assign_xid: 
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+
+step wakeup_bet: 
+	SELECT injection_points_wakeup('before-end-transaction');
+
+injection_points_wakeup
+-----------------------
+                       
+(1 row)
+
+step repack: <... completed>
+step s4_commit: <... completed>
+step s5_commit: 
+	COMMIT;
+
+step check: 
+	TABLE repack_test;
+
+i|j
+-+-
+(0 rows)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
+injection_points_detach
+-----------------------
+                       
+(1 row)
+
diff --git a/src/test/modules/injection_points/specs/repack_running_xacts.spec b/src/test/modules/injection_points/specs/repack_running_xacts.spec
new file mode 100644
index 00000000000..1f878514046
--- /dev/null
+++ b/src/test/modules/injection_points/specs/repack_running_xacts.spec
@@ -0,0 +1,119 @@
+setup
+{
+	CREATE EXTENSION injection_points;
+	CREATE TABLE repack_test(i int PRIMARY KEY, j int);
+	CREATE TABLE aux(i int);
+}
+
+teardown
+{
+	DROP TABLE repack_test;
+	DROP TABLE aux;
+	DROP EXTENSION injection_points;
+}
+
+session s1
+setup
+{
+	SELECT injection_points_attach('before-create-decoding-context', 'wait');
+}
+step repack
+{
+	REPACK (CONCURRENTLY) repack_test;
+}
+step check
+{
+	TABLE repack_test;
+}
+teardown
+{
+	SELECT injection_points_detach('before-create-decoding-context');
+}
+
+session s2
+step wakeup_bcdc
+{
+	SELECT injection_points_wakeup('before-create-decoding-context');
+}
+step wakeup_bet
+{
+	SELECT injection_points_wakeup('before-end-transaction');
+}
+
+session s3
+step s3_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (1);
+}
+step s3_commit
+{
+	COMMIT;
+}
+
+session s4
+step s4_changes
+{
+	BEGIN;
+	INSERT INTO repack_test(i, j) VALUES (1, 1);
+}
+# Do not attach in the setup section, that would be too soon.
+step s4_attach
+{
+	SELECT injection_points_set_local();
+	SELECT injection_points_attach('before-end-transaction', 'wait');
+}
+step s4_commit
+{
+	COMMIT;
+}
+teardown
+{
+	SELECT injection_points_detach('before-end-transaction');
+}
+
+session s5
+step s5_assign_xid
+{
+	BEGIN;
+	INSERT INTO aux VALUES (2);
+}
+step s5_commit
+{
+	COMMIT;
+}
+
+permutation
+repack
+# Assign XID so that a running transaction prevents the snapshot builder from
+# reaching CONSISTENT state immediately. It will wait for this to complete
+# after having reached BUILDING_SNAPSHOT.
+s3_assign_xid
+# Let the decoding setup start.
+wakeup_bcdc
+# Likewise, the snapshot builder will wait for the s4's xact to complete after
+# having reached FULL_SNAPSHOT. This is the problematic transaction, so let it
+# do some changes.
+s4_changes
+# Attach to the 'before-end-transaction' injection point that s4 will need
+# during commit.
+s4_attach
+# Only write commit record for s4, but do not remove the xact from procarray
+# yet. Thus the snapshot builder still needs to wait.
+s4_commit
+# Let the snapshot builder proceed to FULL_SNAPSHOT.
+s3_commit
+# Start another transaction so that CONSISTENT is not reached "directly",
+# i.e. due to no running transaction. It's important here that builder->xmin
+# does not advance.
+s5_assign_xid
+# Remove s4 xact from procarray, and thus reach the CONSISTENT state. Since
+# the COMMIT appeared in WAL too early (i.e. when the snapshot builder state
+# did not allow decoding of COMMIT records yet), the snapshot builder will
+# consider s4 running. This is also due to returning from
+# SnapBuildProcessRunningXacts() too early, w/o advancing builder->xmin.
+wakeup_bet
+# s5 is not needed anymore
+s5_commit
+# Show that the data changes performed by s4 are lost.
+check
-- 
2.47.3


--=-=-=--





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2019-09-15 07:06 [PATCH v13] Make int4 and int8 operations more efficent David Fetter <[email protected]>
2020-03-21 01:47 [PATCH v1 1/2] Report wait event for cost-based vacuum delay Justin Pryzby <[email protected]>
2025-12-09 19:17 [PATCH v3 6/7] Handle pg_get_expr default args in system_functions.sql Mark Wong <[email protected]>
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2025-12-09 19:17 [PATCH v7 5/6] Handle pg_get_expr default args in system_functions.sql Mark Wong <[email protected]>
2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
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2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
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2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
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2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
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2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
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2026-05-12 10:27 [PATCH] Test to demonstrate bug in commit 0d3dba38c7 and to verify a fix. Antonin Houska <[email protected]>
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