Subject: [PATCH v20260912 1/4] Refactor float8out_internval for better performance

From: Andy Fan <[email-masked]>
Date: Wed, 11 Sep 2024 12:19:57 +0800

Some users like cube, geo needs calls float8out_internval to get a
string, and then copy them into its own StringInfo. In this commit,
we would let the user provide a buffer to float8out_internal so that it
can put the data to buffer directly. This commit also reuse the existing
string length to avoid another strlen call in appendStringInfoString.
---
 contrib/cube/cube.c             | 17 +++++++++++++++--
 src/backend/utils/adt/float.c   | 14 ++++++++------
 src/backend/utils/adt/geo_ops.c | 34 ++++++++++++++++++++++-----------
 src/include/catalog/pg_type.h   |  1 +
 src/include/utils/float.h       |  2 +-
 5 files changed, 48 insertions(+), 20 deletions(-)

diff --git a/contrib/cube/cube.c b/contrib/cube/cube.c
index 77263ab277f..a143690092b 100644
--- a/contrib/cube/cube.c
+++ b/contrib/cube/cube.c
@@ -12,6 +12,7 @@
 
 #include "access/gist.h"
 #include "access/stratnum.h"
+#include "catalog/pg_type.h"
 #include "cubedata.h"
 #include "libpq/pqformat.h"
 #include "utils/array.h"
@@ -299,26 +300,38 @@ cube_out(PG_FUNCTION_ARGS)
 	StringInfoData buf;
 	int			dim = DIM(cube);
 	int			i;
+	int str_len;
 
 	initStringInfo(&buf);
 
 	appendStringInfoChar(&buf, '(');
+
+	/* 3 for ", " and 1 for '\0'. */
+	enlargeStringInfo(&buf, (MAXFLOAT8LEN + 4) * dim);
 	for (i = 0; i < dim; i++)
 	{
 		if (i > 0)
 			appendStringInfoString(&buf, ", ");
-		appendStringInfoString(&buf, float8out_internal(LL_COORD(cube, i)));
+		float8out_internal(LL_COORD(cube, i), buf.data + buf.len, &str_len);
+		buf.len += str_len;
+		buf.data[buf.len] = '\0';
 	}
 	appendStringInfoChar(&buf, ')');
 
 	if (!cube_is_point_internal(cube))
 	{
 		appendStringInfoString(&buf, ",(");
+
+		/* 3 for ", " and 1 for '\0'. */
+		enlargeStringInfo(&buf, (MAXFLOAT8LEN + 4) * dim);
 		for (i = 0; i < dim; i++)
 		{
 			if (i > 0)
 				appendStringInfoString(&buf, ", ");
-			appendStringInfoString(&buf, float8out_internal(UR_COORD(cube, i)));
+
+			float8out_internal(UR_COORD(cube, i), buf.data + buf.len, &str_len);
+			buf.len += str_len;
+			buf.data[buf.len] = '\0';
 		}
 		appendStringInfoChar(&buf, ')');
 	}
diff --git a/src/backend/utils/adt/float.c b/src/backend/utils/adt/float.c
index 362c29ab803..13ceade129e 100644
--- a/src/backend/utils/adt/float.c
+++ b/src/backend/utils/adt/float.c
@@ -571,22 +571,24 @@ float8out(PG_FUNCTION_ARGS)
  * float8out_internal - guts of float8out()
  *
  * This is exposed for use by functions that want a reasonably
- * platform-independent way of outputting doubles.
- * The result is always palloc'd.
+ * platform-independent way of outputting doubles, output the
+ * string length to *len;
  */
 char *
-float8out_internal(double num)
+float8out_internal(double num, char *ascii, int *len)
 {
-	char	   *ascii = (char *) palloc(32);
 	int			ndig = DBL_DIG + extra_float_digits;
 
+	if (ascii == NULL)
+		ascii = (char *) palloc(MAXFLOAT8LEN);
+
 	if (extra_float_digits > 0)
 	{
-		double_to_shortest_decimal_buf(num, ascii);
+		*len = double_to_shortest_decimal_buf(num, ascii);
 		return ascii;
 	}
 
-	(void) pg_strfromd(ascii, 32, ndig, num);
+	*len = pg_strfromd(ascii, 32, ndig, num);
 	return ascii;
 }
 
diff --git a/src/backend/utils/adt/geo_ops.c b/src/backend/utils/adt/geo_ops.c
index cc5ce013d0f..212faf08a50 100644
--- a/src/backend/utils/adt/geo_ops.c
+++ b/src/backend/utils/adt/geo_ops.c
@@ -29,6 +29,7 @@
 #include <float.h>
 #include <ctype.h>
 
+#include "catalog/pg_type.h"
 #include "libpq/pqformat.h"
 #include "miscadmin.h"
 #include "nodes/miscnodes.h"
@@ -203,10 +204,12 @@ single_decode(char *num, float8 *x, char **endptr_p,
 static void
 single_encode(float8 x, StringInfo str)
 {
-	char	   *xstr = float8out_internal(x);
+	int str_len;
+	enlargeStringInfo(str, MAXFLOAT8LEN + 1);
+	float8out_internal(x, str->data + str->len, &str_len);
 
-	appendStringInfoString(str, xstr);
-	pfree(xstr);
+	str->len += str_len;
+	str->data[str->len] = '\0';
 }								/* single_encode() */
 
 static bool
@@ -255,12 +258,20 @@ fail:
 static void
 pair_encode(float8 x, float8 y, StringInfo str)
 {
-	char	   *xstr = float8out_internal(x);
-	char	   *ystr = float8out_internal(y);
+	int data_len;
+	/* the additional 2 is for ',' and '\0' */
+	enlargeStringInfo(str, MAXFLOAT8LEN * 2 + 2);
 
-	appendStringInfo(str, "%s,%s", xstr, ystr);
-	pfree(xstr);
-	pfree(ystr);
+	float8out_internal(x, str->data + str->len, &data_len);
+	str->len += data_len;
+
+	str->data[str->len] = ',';
+	str->len++;
+
+	float8out_internal(y, str->data + str->len, &data_len);
+	str->len += data_len;
+
+	str->data[str->len] = '\0';
 }
 
 static bool
@@ -1041,9 +1052,10 @@ Datum
 line_out(PG_FUNCTION_ARGS)
 {
 	LINE	   *line = PG_GETARG_LINE_P(0);
-	char	   *astr = float8out_internal(line->A);
-	char	   *bstr = float8out_internal(line->B);
-	char	   *cstr = float8out_internal(line->C);
+	int datalen;
+	char	   *astr = float8out_internal(line->A, NULL, &datalen);
+	char	   *bstr = float8out_internal(line->B, NULL, &datalen);
+	char	   *cstr = float8out_internal(line->C, NULL, &datalen);
 
 	PG_RETURN_CSTRING(psprintf("%c%s%c%s%c%s%c", LDELIM_L, astr, DELIM, bstr,
 							   DELIM, cstr, RDELIM_L));
diff --git a/src/include/catalog/pg_type.h b/src/include/catalog/pg_type.h
index 74183ec5a2e..b3858188131 100644
--- a/src/include/catalog/pg_type.h
+++ b/src/include/catalog/pg_type.h
@@ -348,6 +348,7 @@ MAKE_SYSCACHE(TYPENAMENSP, pg_type_typname_nsp_index, 64);
 
 #endif							/* EXPOSE_TO_CLIENT_CODE */
 
+#define MAXFLOAT8LEN 32
 
 extern ObjectAddress TypeShellMake(const char *typeName,
 								   Oid typeNamespace,
diff --git a/src/include/utils/float.h b/src/include/utils/float.h
index ffa743d6273..69661a7071f 100644
--- a/src/include/utils/float.h
+++ b/src/include/utils/float.h
@@ -43,7 +43,7 @@ extern float8 float8in_internal(char *num, char **endptr_p,
 extern float4 float4in_internal(char *num, char **endptr_p,
 								const char *type_name, const char *orig_string,
 								struct Node *escontext);
-extern char *float8out_internal(float8 num);
+extern char *float8out_internal(float8 num, char *ascii, int *len);
 extern int	float4_cmp_internal(float4 a, float4 b);
 extern int	float8_cmp_internal(float8 a, float8 b);
 
-- 
2.43.0

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 filename=v20260912-0002-Continue-to-remove-some-unnecesary-strlen-.patch