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[PATCH v18 1/8] Row pattern recognition patch for raw parser.
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* [PATCH v18 1/8] Row pattern recognition patch for raw parser.
@ 2024-05-11 07:11 Tatsuo Ishii <ishii@postgresql.org>
  0 siblings, 0 replies; 647+ messages in thread

From: Tatsuo Ishii @ 2024-05-11 07:11 UTC (permalink / raw)

---
 src/backend/parser/gram.y       | 221 ++++++++++++++++++++++++++++++--
 src/include/nodes/parsenodes.h  |  67 ++++++++++
 src/include/parser/kwlist.h     |   8 ++
 src/include/parser/parse_node.h |   1 +
 4 files changed, 285 insertions(+), 12 deletions(-)

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index e8b619926e..c09a0f7e4f 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -680,6 +680,21 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 				json_object_constructor_null_clause_opt
 				json_array_constructor_null_clause_opt
 
+%type <target>	row_pattern_measure_item
+				row_pattern_definition
+%type <node>	opt_row_pattern_common_syntax
+				opt_row_pattern_skip_to
+				row_pattern_subset_item
+				row_pattern_term
+%type <list>	opt_row_pattern_measures
+				row_pattern_measure_list
+				row_pattern_definition_list
+				opt_row_pattern_subset_clause
+				row_pattern_subset_list
+				row_pattern_subset_rhs
+				row_pattern
+%type <boolean>	opt_row_pattern_initial_or_seek
+				first_or_last
 
 /*
  * Non-keyword token types.  These are hard-wired into the "flex" lexer.
@@ -723,7 +738,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	CURRENT_TIME CURRENT_TIMESTAMP CURRENT_USER CURSOR CYCLE
 
 	DATA_P DATABASE DAY_P DEALLOCATE DEC DECIMAL_P DECLARE DEFAULT DEFAULTS
-	DEFERRABLE DEFERRED DEFINER DELETE_P DELIMITER DELIMITERS DEPENDS DEPTH DESC
+	DEFERRABLE DEFERRED DEFINE DEFINER DELETE_P DELIMITER DELIMITERS DEPENDS DEPTH DESC
 	DETACH DICTIONARY DISABLE_P DISCARD DISTINCT DO DOCUMENT_P DOMAIN_P
 	DOUBLE_P DROP
 
@@ -739,7 +754,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
 	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
-	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
+	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIAL INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
 
@@ -752,7 +767,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	LEADING LEAKPROOF LEAST LEFT LEVEL LIKE LIMIT LISTEN LOAD LOCAL
 	LOCALTIME LOCALTIMESTAMP LOCATION LOCK_P LOCKED LOGGED
 
-	MAPPING MATCH MATCHED MATERIALIZED MAXVALUE MERGE MERGE_ACTION METHOD
+	MAPPING MATCH MATCHED MATERIALIZED MAXVALUE MEASURES MERGE MERGE_ACTION METHOD
 	MINUTE_P MINVALUE MODE MONTH_P MOVE
 
 	NAME_P NAMES NATIONAL NATURAL NCHAR NESTED NEW NEXT NFC NFD NFKC NFKD NO
@@ -764,9 +779,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	ORDER ORDINALITY OTHERS OUT_P OUTER_P
 	OVER OVERLAPS OVERLAY OVERRIDING OWNED OWNER
 
-	PARALLEL PARAMETER PARSER PARTIAL PARTITION PARTITIONS PASSING PASSWORD PATH
-	PERIOD PLACING PLAN PLANS POLICY
-
+	PARALLEL PARAMETER PARSER PARTIAL PARTITION PARTITIONS PASSING PASSWORD PAST
+	PATH PATTERN_P PERIOD PERMUTE PLACING PLAN PLANS POLICY
 	POSITION PRECEDING PRECISION PRESERVE PREPARE PREPARED PRIMARY
 	PRIOR PRIVILEGES PROCEDURAL PROCEDURE PROCEDURES PROGRAM PUBLICATION
 
@@ -777,12 +791,13 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
-	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
+	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SEEK SELECT
 	SEQUENCE SEQUENCES
+
 	SERIALIZABLE SERVER SESSION SESSION_USER SET SETS SETOF SHARE SHOW
 	SIMILAR SIMPLE SKIP SMALLINT SNAPSHOT SOME SPLIT SOURCE SQL_P STABLE STANDALONE_P
 	START STATEMENT STATISTICS STDIN STDOUT STORAGE STORED STRICT_P STRING_P STRIP_P
-	SUBSCRIPTION SUBSTRING SUPPORT SYMMETRIC SYSID SYSTEM_P SYSTEM_USER
+	SUBSCRIPTION SUBSET SUBSTRING SUPPORT SYMMETRIC SYSID SYSTEM_P SYSTEM_USER
 
 	TABLE TABLES TABLESAMPLE TABLESPACE TARGET TEMP TEMPLATE TEMPORARY TEXT_P THEN
 	TIES TIME TIMESTAMP TO TRAILING TRANSACTION TRANSFORM
@@ -891,6 +906,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %nonassoc	UNBOUNDED NESTED /* ideally would have same precedence as IDENT */
 %nonassoc	IDENT PARTITION RANGE ROWS GROUPS PRECEDING FOLLOWING CUBE ROLLUP
 			SET KEYS OBJECT_P SCALAR VALUE_P WITH WITHOUT PATH
+			MEASURES AFTER INITIAL SEEK PATTERN_P
 %left		Op OPERATOR		/* multi-character ops and user-defined operators */
 %left		'+' '-'
 %left		'*' '/' '%'
@@ -16333,7 +16349,8 @@ over_clause: OVER window_specification
 		;
 
 window_specification: '(' opt_existing_window_name opt_partition_clause
-						opt_sort_clause opt_frame_clause ')'
+						opt_sort_clause opt_row_pattern_measures opt_frame_clause
+						opt_row_pattern_common_syntax ')'
 				{
 					WindowDef  *n = makeNode(WindowDef);
 
@@ -16341,10 +16358,12 @@ window_specification: '(' opt_existing_window_name opt_partition_clause
 					n->refname = $2;
 					n->partitionClause = $3;
 					n->orderClause = $4;
+					n->rowPatternMeasures = $5;
 					/* copy relevant fields of opt_frame_clause */
-					n->frameOptions = $5->frameOptions;
-					n->startOffset = $5->startOffset;
-					n->endOffset = $5->endOffset;
+					n->frameOptions = $6->frameOptions;
+					n->startOffset = $6->startOffset;
+					n->endOffset = $6->endOffset;
+					n->rpCommonSyntax = (RPCommonSyntax *)$7;
 					n->location = @1;
 					$$ = n;
 				}
@@ -16368,6 +16387,31 @@ opt_partition_clause: PARTITION BY expr_list		{ $$ = $3; }
 			| /*EMPTY*/								{ $$ = NIL; }
 		;
 
+/*
+ * ROW PATTERN_P MEASURES
+ */
+opt_row_pattern_measures: MEASURES row_pattern_measure_list	{ $$ = $2; }
+			| /*EMPTY*/								{ $$ = NIL; }
+		;
+
+row_pattern_measure_list:
+			row_pattern_measure_item
+					{ $$ = list_make1($1); }
+			| row_pattern_measure_list ',' row_pattern_measure_item
+					{ $$ = lappend($1, $3); }
+		;
+
+row_pattern_measure_item:
+			a_expr AS ColLabel
+				{
+					$$ = makeNode(ResTarget);
+					$$->name = $3;
+					$$->indirection = NIL;
+					$$->val = (Node *) $1;
+					$$->location = @1;
+				}
+		;
+
 /*
  * For frame clauses, we return a WindowDef, but only some fields are used:
  * frameOptions, startOffset, and endOffset.
@@ -16527,6 +16571,143 @@ opt_window_exclusion_clause:
 			| /*EMPTY*/				{ $$ = 0; }
 		;
 
+opt_row_pattern_common_syntax:
+opt_row_pattern_skip_to opt_row_pattern_initial_or_seek
+				PATTERN_P '(' row_pattern ')'
+				opt_row_pattern_subset_clause
+				DEFINE row_pattern_definition_list
+			{
+				RPCommonSyntax *n = makeNode(RPCommonSyntax);
+				n->rpSkipTo = ((RPCommonSyntax *)$1)->rpSkipTo;
+				n->rpSkipVariable = ((RPCommonSyntax *)$1)->rpSkipVariable;
+				n->initial = $2;
+				n->rpPatterns = $5;
+				n->rpSubsetClause = $7;
+				n->rpDefs = $9;
+				$$ = (Node *) n;
+			}
+			| /*EMPTY*/		{ $$ = NULL; }
+	;
+
+opt_row_pattern_skip_to:
+			AFTER MATCH SKIP TO NEXT ROW
+				{
+					RPCommonSyntax *n = makeNode(RPCommonSyntax);
+					n->rpSkipTo = ST_NEXT_ROW;
+					n->rpSkipVariable = NULL;
+					$$ = (Node *) n;
+			}
+			| AFTER MATCH SKIP PAST LAST_P ROW
+				{
+					RPCommonSyntax *n = makeNode(RPCommonSyntax);
+					n->rpSkipTo = ST_PAST_LAST_ROW;
+					n->rpSkipVariable = NULL;
+					$$ = (Node *) n;
+				}
+			| AFTER MATCH SKIP TO first_or_last ColId
+				{
+					RPCommonSyntax *n = makeNode(RPCommonSyntax);
+					n->rpSkipTo = $5? ST_FIRST_VARIABLE : ST_LAST_VARIABLE;
+					n->rpSkipVariable = $6;
+					$$ = (Node *) n;
+				}
+/*
+			| AFTER MATCH SKIP TO LAST_P ColId		%prec LAST_P
+				{
+					RPCommonSyntax *n = makeNode(RPCommonSyntax);
+					n->rpSkipTo = ST_LAST_VARIABLE;
+					n->rpSkipVariable = $6;
+					$$ = n;
+				}
+			| AFTER MATCH SKIP TO ColId
+				{
+					RPCommonSyntax *n = makeNode(RPCommonSyntax);
+					n->rpSkipTo = ST_VARIABLE;
+					n->rpSkipVariable = $5;
+					$$ = n;
+				}
+*/
+			| /*EMPTY*/
+				{
+					RPCommonSyntax *n = makeNode(RPCommonSyntax);
+					/* temporary set default to ST_NEXT_ROW */
+					n->rpSkipTo = ST_PAST_LAST_ROW;
+					n->rpSkipVariable = NULL;
+					$$ = (Node *) n;
+				}
+	;
+
+first_or_last:
+			FIRST_P		{ $$ = true; }
+			| LAST_P	{ $$ = false; }
+	;
+
+opt_row_pattern_initial_or_seek:
+			INITIAL			{ $$ = true; }
+			| SEEK
+				{
+					ereport(ERROR,
+							(errcode(ERRCODE_SYNTAX_ERROR),
+							 errmsg("SEEK is not supported"),
+							 errhint("Use INITIAL."),
+							 parser_errposition(@1)));
+				}
+			| /*EMPTY*/		{ $$ = true; }
+		;
+
+row_pattern:
+			row_pattern_term							{ $$ = list_make1($1); }
+			| row_pattern row_pattern_term				{ $$ = lappend($1, $2); }
+		;
+
+row_pattern_term:
+			ColId	{ $$ = (Node *) makeSimpleA_Expr(AEXPR_OP, "", (Node *)makeString($1), NULL, @1); }
+			| ColId '*'	{ $$ = (Node *) makeSimpleA_Expr(AEXPR_OP, "*", (Node *)makeString($1), NULL, @1); }
+			| ColId '+'	{ $$ = (Node *) makeSimpleA_Expr(AEXPR_OP, "+", (Node *)makeString($1), NULL, @1); }
+			| ColId '?'	{ $$ = (Node *) makeSimpleA_Expr(AEXPR_OP, "?", (Node *)makeString($1), NULL, @1); }
+		;
+
+opt_row_pattern_subset_clause:
+			SUBSET row_pattern_subset_list	{ $$ = $2; }
+			| /*EMPTY*/												{ $$ = NIL; }
+		;
+
+row_pattern_subset_list:
+			row_pattern_subset_item									{ $$ = list_make1($1); }
+			| row_pattern_subset_list ',' row_pattern_subset_item	{ $$ = lappend($1, $3); }
+			| /*EMPTY*/												{ $$ = NIL; }
+		;
+
+row_pattern_subset_item: ColId '=' '(' row_pattern_subset_rhs ')'
+			{
+				RPSubsetItem *n = makeNode(RPSubsetItem);
+				n->name = $1;
+				n->rhsVariable = $4;
+				$$ = (Node *) n;
+			}
+		;
+
+row_pattern_subset_rhs:
+			ColId								{ $$ = list_make1(makeStringConst($1, @1)); }
+			| row_pattern_subset_rhs ',' ColId	{ $$ = lappend($1, makeStringConst($3, @1)); }
+			| /*EMPTY*/							{ $$ = NIL; }
+		;
+
+row_pattern_definition_list:
+			row_pattern_definition										{ $$ = list_make1($1); }
+			| row_pattern_definition_list ',' row_pattern_definition	{ $$ = lappend($1, $3); }
+		;
+
+row_pattern_definition:
+			ColId AS a_expr
+				{
+					$$ = makeNode(ResTarget);
+					$$->name = $1;
+					$$->indirection = NIL;
+					$$->val = (Node *) $3;
+					$$->location = @1;
+				}
+		;
 
 /*
  * Supporting nonterminals for expressions.
@@ -17737,6 +17918,7 @@ unreserved_keyword:
 			| INDEXES
 			| INHERIT
 			| INHERITS
+			| INITIAL
 			| INLINE_P
 			| INPUT_P
 			| INSENSITIVE
@@ -17765,6 +17947,7 @@ unreserved_keyword:
 			| MATCHED
 			| MATERIALIZED
 			| MAXVALUE
+			| MEASURES
 			| MERGE
 			| METHOD
 			| MINUTE_P
@@ -17810,8 +17993,11 @@ unreserved_keyword:
 			| PARTITIONS
 			| PASSING
 			| PASSWORD
+			| PAST
 			| PATH
+			| PATTERN_P
 			| PERIOD
+			| PERMUTE
 			| PLAN
 			| PLANS
 			| POLICY
@@ -17864,6 +18050,7 @@ unreserved_keyword:
 			| SEARCH
 			| SECOND_P
 			| SECURITY
+			| SEEK
 			| SEQUENCE
 			| SEQUENCES
 			| SERIALIZABLE
@@ -17892,6 +18079,7 @@ unreserved_keyword:
 			| STRING_P
 			| STRIP_P
 			| SUBSCRIPTION
+			| SUBSET
 			| SUPPORT
 			| SYSID
 			| SYSTEM_P
@@ -18086,6 +18274,7 @@ reserved_keyword:
 			| CURRENT_USER
 			| DEFAULT
 			| DEFERRABLE
+			| DEFINE
 			| DESC
 			| DISTINCT
 			| DO
@@ -18249,6 +18438,7 @@ bare_label_keyword:
 			| DEFAULTS
 			| DEFERRABLE
 			| DEFERRED
+			| DEFINE
 			| DEFINER
 			| DELETE_P
 			| DELIMITER
@@ -18326,6 +18516,7 @@ bare_label_keyword:
 			| INDEXES
 			| INHERIT
 			| INHERITS
+			| INITIAL
 			| INITIALLY
 			| INLINE_P
 			| INNER_P
@@ -18380,6 +18571,7 @@ bare_label_keyword:
 			| MATCHED
 			| MATERIALIZED
 			| MAXVALUE
+			| MEASURES
 			| MERGE
 			| MERGE_ACTION
 			| METHOD
@@ -18437,8 +18629,11 @@ bare_label_keyword:
 			| PARTITIONS
 			| PASSING
 			| PASSWORD
+			| PAST
 			| PATH
+			| PATTERN_P
 			| PERIOD
+			| PERMUTE
 			| PLACING
 			| PLAN
 			| PLANS
@@ -18497,6 +18692,7 @@ bare_label_keyword:
 			| SCROLL
 			| SEARCH
 			| SECURITY
+			| SEEK
 			| SELECT
 			| SEQUENCE
 			| SEQUENCES
@@ -18531,6 +18727,7 @@ bare_label_keyword:
 			| STRING_P
 			| STRIP_P
 			| SUBSCRIPTION
+			| SUBSET
 			| SUBSTRING
 			| SUPPORT
 			| SYMMETRIC
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 3ca06fc3af..9e65e9132c 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -550,6 +550,48 @@ typedef struct SortBy
 	ParseLoc	location;		/* operator location, or -1 if none/unknown */
 } SortBy;
 
+/*
+ * AFTER MATCH row pattern skip to types in row pattern common syntax
+ */
+typedef enum RPSkipTo
+{
+	ST_NONE,					/* AFTER MATCH omitted */
+	ST_NEXT_ROW,				/* SKIP TO NEXT ROW */
+	ST_PAST_LAST_ROW,			/* SKIP TO PAST LAST ROW */
+	ST_FIRST_VARIABLE,			/* SKIP TO FIRST variable name */
+	ST_LAST_VARIABLE,			/* SKIP TO LAST variable name */
+	ST_VARIABLE					/* SKIP TO variable name */
+}			RPSkipTo;
+
+/*
+ * Row Pattern SUBSET clause item
+ */
+typedef struct RPSubsetItem
+{
+	NodeTag		type;
+	char	   *name;			/* Row Pattern SUBSET clause variable name */
+	List	   *rhsVariable;	/* Row Pattern SUBSET rhs variables (list of
+								 * char *string) */
+}			RPSubsetItem;
+
+/*
+ * RowPatternCommonSyntax - raw representation of row pattern common syntax
+ *
+ */
+typedef struct RPCommonSyntax
+{
+	NodeTag		type;
+	RPSkipTo	rpSkipTo;		/* Row Pattern AFTER MATCH SKIP type */
+	char	   *rpSkipVariable; /* Row Pattern Skip To variable name, if any */
+	bool		initial;		/* true if <row pattern initial or seek> is
+								 * initial */
+	List	   *rpPatterns;		/* PATTERN variables (list of A_Expr) */
+	List	   *rpSubsetClause; /* row pattern subset clause (list of
+								 * RPSubsetItem), if any */
+	List	   *rpDefs;			/* row pattern definitions clause (list of
+								 * ResTarget) */
+}			RPCommonSyntax;
+
 /*
  * WindowDef - raw representation of WINDOW and OVER clauses
  *
@@ -565,6 +607,9 @@ typedef struct WindowDef
 	char	   *refname;		/* referenced window name, if any */
 	List	   *partitionClause;	/* PARTITION BY expression list */
 	List	   *orderClause;	/* ORDER BY (list of SortBy) */
+	List	   *rowPatternMeasures; /* row pattern measures (list of
+									 * ResTarget) */
+	RPCommonSyntax *rpCommonSyntax; /* row pattern common syntax */
 	int			frameOptions;	/* frame_clause options, see below */
 	Node	   *startOffset;	/* expression for starting bound, if any */
 	Node	   *endOffset;		/* expression for ending bound, if any */
@@ -1533,6 +1578,11 @@ typedef struct GroupingSet
  * the orderClause might or might not be copied (see copiedOrder); the framing
  * options are never copied, per spec.
  *
+ * "defineClause" is Row Pattern Recognition DEFINE clause (list of
+ * TargetEntry). TargetEntry.resname represents row pattern definition
+ * variable name. "patternVariable" and "patternRegexp" represents PATTERN
+ * clause.
+ *
  * The information relevant for the query jumbling is the partition clause
  * type and its bounds.
  */
@@ -1562,6 +1612,23 @@ typedef struct WindowClause
 	Index		winref;			/* ID referenced by window functions */
 	/* did we copy orderClause from refname? */
 	bool		copiedOrder pg_node_attr(query_jumble_ignore);
+	/* Row Pattern AFTER MACH SKIP clause */
+	RPSkipTo	rpSkipTo;		/* Row Pattern Skip To type */
+	char	   *rpSkipVariable; /* Row Pattern Skip To variable */
+	bool		initial;		/* true if <row pattern initial or seek> is
+								 * initial */
+	/* Row Pattern DEFINE clause (list of TargetEntry) */
+	List	   *defineClause;
+	/* Row Pattern DEFINE variable initial names (list of String) */
+	List	   *defineInitial;
+	/* Row Pattern PATTERN variable name (list of String) */
+	List	   *patternVariable;
+
+	/*
+	 * Row Pattern PATTERN regular expression quantifier ('+' or ''. list of
+	 * String)
+	 */
+	List	   *patternRegexp;
 } WindowClause;
 
 /*
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index f9a4afd472..df49492629 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -129,6 +129,7 @@ PG_KEYWORD("default", DEFAULT, RESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("defaults", DEFAULTS, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("deferrable", DEFERRABLE, RESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("deferred", DEFERRED, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("define", DEFINE, RESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("definer", DEFINER, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("delete", DELETE_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("delimiter", DELIMITER, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -215,6 +216,7 @@ PG_KEYWORD("index", INDEX, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("indexes", INDEXES, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("inherit", INHERIT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("inherits", INHERITS, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("initial", INITIAL, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("initially", INITIALLY, RESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("inline", INLINE_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("inner", INNER_P, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
@@ -273,6 +275,7 @@ PG_KEYWORD("match", MATCH, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("matched", MATCHED, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("materialized", MATERIALIZED, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("maxvalue", MAXVALUE, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("measures", MEASURES, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("merge", MERGE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("merge_action", MERGE_ACTION, COL_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("method", METHOD, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -338,8 +341,11 @@ PG_KEYWORD("partition", PARTITION, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("partitions", PARTITIONS, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("passing", PASSING, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("password", PASSWORD, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("past", PAST, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("path", PATH, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("pattern", PATTERN_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("period", PERIOD, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("permute", PERMUTE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("placing", PLACING, RESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("plan", PLAN, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("plans", PLANS, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -401,6 +407,7 @@ PG_KEYWORD("scroll", SCROLL, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("search", SEARCH, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("second", SECOND_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("security", SECURITY, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("seek", SEEK, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("select", SELECT, RESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("sequence", SEQUENCE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("sequences", SEQUENCES, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -435,6 +442,7 @@ PG_KEYWORD("strict", STRICT_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("string", STRING_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("strip", STRIP_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("subscription", SUBSCRIPTION, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("subset", SUBSET, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("substring", SUBSTRING, COL_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("support", SUPPORT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("symmetric", SYMMETRIC, RESERVED_KEYWORD, BARE_LABEL)
diff --git a/src/include/parser/parse_node.h b/src/include/parser/parse_node.h
index 5b781d87a9..66935afff8 100644
--- a/src/include/parser/parse_node.h
+++ b/src/include/parser/parse_node.h
@@ -51,6 +51,7 @@ typedef enum ParseExprKind
 	EXPR_KIND_WINDOW_FRAME_RANGE,	/* window frame clause with RANGE */
 	EXPR_KIND_WINDOW_FRAME_ROWS,	/* window frame clause with ROWS */
 	EXPR_KIND_WINDOW_FRAME_GROUPS,	/* window frame clause with GROUPS */
+	EXPR_KIND_RPR_DEFINE,		/* DEFINE */
 	EXPR_KIND_SELECT_TARGET,	/* SELECT target list item */
 	EXPR_KIND_INSERT_TARGET,	/* INSERT target list item */
 	EXPR_KIND_UPDATE_SOURCE,	/* UPDATE assignment source item */
-- 
2.25.1


----Next_Part(Sat_May_11_16_23_07_2024_789)--
Content-Type: Text/X-Patch; charset=us-ascii
Content-Transfer-Encoding: 7bit
Content-Disposition: inline;
 filename="v18-0002-Row-pattern-recognition-patch-parse-analysis.patch"



^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v5 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  65 +++++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 231 insertions(+)
  49.8% doc/src/sgml/
   3.1% src/backend/catalog/
  25.8% src/backend/utils/adt/
   6.8% src/include/catalog/
   9.2% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index bb75ed1069b..86200553293 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1195,6 +1209,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -5342,6 +5441,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index e54018004db..e005eaeb579 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -946,6 +946,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 9185a8e6b83..77ee9222ccf 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -708,6 +708,71 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns transactions statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		/* check if the backend type tracks statistics */
+		if (!pgstat_tracks_backend_bktype(beentry->st_backendType))
+			continue;
+
+		/*
+		 * Don't use pgstat_fetch_stat_backend_by_pid() to avoid holding the
+		 * ProcArrayLock during each iteration.
+		 */
+		backend_stats = pgstat_fetch_stat_backend(local_beentry->proc_number);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3579cec5744..6a686e93fdd 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5680,6 +5680,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 2b3cf6d8569..2b4ea519677 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1860,6 +1860,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index ea7f7846895..e3f55a4c0ea 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 65d8968c83e..e6b35593a95 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--uN5gGi2rtCNSVbpC--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v4 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.7% doc/src/sgml/
   3.2% src/backend/catalog/
  23.1% src/backend/utils/adt/
   7.0% src/include/catalog/
   9.6% src/test/regress/expected/
   5.1% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..025641c2f70 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..ee3f653f360 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..fa92099e789 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..24ec3d861a2 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..ae376f96998 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..7079198bc06 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..0d6a408c7b5 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--jg9kqX3osLGO+8A7--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v5 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  65 +++++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 231 insertions(+)
  49.8% doc/src/sgml/
   3.1% src/backend/catalog/
  25.8% src/backend/utils/adt/
   6.8% src/include/catalog/
   9.2% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index bb75ed1069b..86200553293 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1195,6 +1209,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -5342,6 +5441,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index e54018004db..e005eaeb579 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -946,6 +946,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 9185a8e6b83..77ee9222ccf 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -708,6 +708,71 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns transactions statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		/* check if the backend type tracks statistics */
+		if (!pgstat_tracks_backend_bktype(beentry->st_backendType))
+			continue;
+
+		/*
+		 * Don't use pgstat_fetch_stat_backend_by_pid() to avoid holding the
+		 * ProcArrayLock during each iteration.
+		 */
+		backend_stats = pgstat_fetch_stat_backend(local_beentry->proc_number);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3579cec5744..6a686e93fdd 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5680,6 +5680,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 2b3cf6d8569..2b4ea519677 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1860,6 +1860,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index ea7f7846895..e3f55a4c0ea 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 65d8968c83e..e6b35593a95 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--uN5gGi2rtCNSVbpC--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v5 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  65 +++++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 231 insertions(+)
  49.8% doc/src/sgml/
   3.1% src/backend/catalog/
  25.8% src/backend/utils/adt/
   6.8% src/include/catalog/
   9.2% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index bb75ed1069b..86200553293 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1195,6 +1209,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -5342,6 +5441,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index e54018004db..e005eaeb579 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -946,6 +946,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 9185a8e6b83..77ee9222ccf 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -708,6 +708,71 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns transactions statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		/* check if the backend type tracks statistics */
+		if (!pgstat_tracks_backend_bktype(beentry->st_backendType))
+			continue;
+
+		/*
+		 * Don't use pgstat_fetch_stat_backend_by_pid() to avoid holding the
+		 * ProcArrayLock during each iteration.
+		 */
+		backend_stats = pgstat_fetch_stat_backend(local_beentry->proc_number);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3579cec5744..6a686e93fdd 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5680,6 +5680,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 2b3cf6d8569..2b4ea519677 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1860,6 +1860,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index ea7f7846895..e3f55a4c0ea 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 65d8968c83e..e6b35593a95 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--uN5gGi2rtCNSVbpC--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v5 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  65 +++++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 231 insertions(+)
  49.8% doc/src/sgml/
   3.1% src/backend/catalog/
  25.8% src/backend/utils/adt/
   6.8% src/include/catalog/
   9.2% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index bb75ed1069b..86200553293 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1195,6 +1209,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -5342,6 +5441,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index e54018004db..e005eaeb579 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -946,6 +946,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 9185a8e6b83..77ee9222ccf 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -708,6 +708,71 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns transactions statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		/* check if the backend type tracks statistics */
+		if (!pgstat_tracks_backend_bktype(beentry->st_backendType))
+			continue;
+
+		/*
+		 * Don't use pgstat_fetch_stat_backend_by_pid() to avoid holding the
+		 * ProcArrayLock during each iteration.
+		 */
+		backend_stats = pgstat_fetch_stat_backend(local_beentry->proc_number);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3579cec5744..6a686e93fdd 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5680,6 +5680,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 2b3cf6d8569..2b4ea519677 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1860,6 +1860,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index ea7f7846895..e3f55a4c0ea 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 65d8968c83e..e6b35593a95 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--uN5gGi2rtCNSVbpC--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v5 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  65 +++++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 231 insertions(+)
  49.8% doc/src/sgml/
   3.1% src/backend/catalog/
  25.8% src/backend/utils/adt/
   6.8% src/include/catalog/
   9.2% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index bb75ed1069b..86200553293 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1195,6 +1209,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -5342,6 +5441,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index e54018004db..e005eaeb579 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -946,6 +946,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 9185a8e6b83..77ee9222ccf 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -708,6 +708,71 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns transactions statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		/* check if the backend type tracks statistics */
+		if (!pgstat_tracks_backend_bktype(beentry->st_backendType))
+			continue;
+
+		/*
+		 * Don't use pgstat_fetch_stat_backend_by_pid() to avoid holding the
+		 * ProcArrayLock during each iteration.
+		 */
+		backend_stats = pgstat_fetch_stat_backend(local_beentry->proc_number);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3579cec5744..6a686e93fdd 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5680,6 +5680,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 2b3cf6d8569..2b4ea519677 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1860,6 +1860,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index ea7f7846895..e3f55a4c0ea 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 65d8968c83e..e6b35593a95 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--uN5gGi2rtCNSVbpC--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v4 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.7% doc/src/sgml/
   3.2% src/backend/catalog/
  23.1% src/backend/utils/adt/
   7.0% src/include/catalog/
   9.6% src/test/regress/expected/
   5.1% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..025641c2f70 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..ee3f653f360 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..fa92099e789 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..24ec3d861a2 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..ae376f96998 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..7079198bc06 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..0d6a408c7b5 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--jg9kqX3osLGO+8A7--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v4 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.7% doc/src/sgml/
   3.2% src/backend/catalog/
  23.1% src/backend/utils/adt/
   7.0% src/include/catalog/
   9.6% src/test/regress/expected/
   5.1% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..025641c2f70 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..ee3f653f360 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..fa92099e789 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..24ec3d861a2 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..ae376f96998 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..7079198bc06 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..0d6a408c7b5 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--jg9kqX3osLGO+8A7--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v4 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.7% doc/src/sgml/
   3.2% src/backend/catalog/
  23.1% src/backend/utils/adt/
   7.0% src/include/catalog/
   9.6% src/test/regress/expected/
   5.1% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..025641c2f70 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..ee3f653f360 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..fa92099e789 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..24ec3d861a2 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..ae376f96998 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..7079198bc06 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..0d6a408c7b5 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--jg9kqX3osLGO+8A7--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v5 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  65 +++++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 231 insertions(+)
  49.8% doc/src/sgml/
   3.1% src/backend/catalog/
  25.8% src/backend/utils/adt/
   6.8% src/include/catalog/
   9.2% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index bb75ed1069b..86200553293 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1195,6 +1209,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -5342,6 +5441,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index e54018004db..e005eaeb579 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -946,6 +946,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 9185a8e6b83..77ee9222ccf 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -708,6 +708,71 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns transactions statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		/* check if the backend type tracks statistics */
+		if (!pgstat_tracks_backend_bktype(beentry->st_backendType))
+			continue;
+
+		/*
+		 * Don't use pgstat_fetch_stat_backend_by_pid() to avoid holding the
+		 * ProcArrayLock during each iteration.
+		 */
+		backend_stats = pgstat_fetch_stat_backend(local_beentry->proc_number);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3579cec5744..6a686e93fdd 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5680,6 +5680,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 2b3cf6d8569..2b4ea519677 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1860,6 +1860,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index ea7f7846895..e3f55a4c0ea 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 65d8968c83e..e6b35593a95 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--uN5gGi2rtCNSVbpC--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v4 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.7% doc/src/sgml/
   3.2% src/backend/catalog/
  23.1% src/backend/utils/adt/
   7.0% src/include/catalog/
   9.6% src/test/regress/expected/
   5.1% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..025641c2f70 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..ee3f653f360 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..fa92099e789 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..24ec3d861a2 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..ae376f96998 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..7079198bc06 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..0d6a408c7b5 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--jg9kqX3osLGO+8A7--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v4 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.7% doc/src/sgml/
   3.2% src/backend/catalog/
  23.1% src/backend/utils/adt/
   7.0% src/include/catalog/
   9.6% src/test/regress/expected/
   5.1% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..025641c2f70 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..ee3f653f360 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..fa92099e789 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..24ec3d861a2 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..ae376f96998 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..7079198bc06 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..0d6a408c7b5 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--jg9kqX3osLGO+8A7--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v4 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.7% doc/src/sgml/
   3.2% src/backend/catalog/
  23.1% src/backend/utils/adt/
   7.0% src/include/catalog/
   9.6% src/test/regress/expected/
   5.1% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..025641c2f70 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..ee3f653f360 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..fa92099e789 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..24ec3d861a2 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..ae376f96998 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..7079198bc06 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..0d6a408c7b5 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--jg9kqX3osLGO+8A7--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v5 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  65 +++++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 231 insertions(+)
  49.8% doc/src/sgml/
   3.1% src/backend/catalog/
  25.8% src/backend/utils/adt/
   6.8% src/include/catalog/
   9.2% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index bb75ed1069b..86200553293 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1195,6 +1209,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -5342,6 +5441,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index e54018004db..e005eaeb579 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -946,6 +946,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 9185a8e6b83..77ee9222ccf 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -708,6 +708,71 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns transactions statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		/* check if the backend type tracks statistics */
+		if (!pgstat_tracks_backend_bktype(beentry->st_backendType))
+			continue;
+
+		/*
+		 * Don't use pgstat_fetch_stat_backend_by_pid() to avoid holding the
+		 * ProcArrayLock during each iteration.
+		 */
+		backend_stats = pgstat_fetch_stat_backend(local_beentry->proc_number);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3579cec5744..6a686e93fdd 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5680,6 +5680,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 2b3cf6d8569..2b4ea519677 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1860,6 +1860,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index ea7f7846895..e3f55a4c0ea 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 65d8968c83e..e6b35593a95 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--uN5gGi2rtCNSVbpC--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v5 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  65 +++++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 231 insertions(+)
  49.8% doc/src/sgml/
   3.1% src/backend/catalog/
  25.8% src/backend/utils/adt/
   6.8% src/include/catalog/
   9.2% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index bb75ed1069b..86200553293 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1195,6 +1209,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -5342,6 +5441,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index e54018004db..e005eaeb579 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -946,6 +946,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 9185a8e6b83..77ee9222ccf 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -708,6 +708,71 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns transactions statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		/* check if the backend type tracks statistics */
+		if (!pgstat_tracks_backend_bktype(beentry->st_backendType))
+			continue;
+
+		/*
+		 * Don't use pgstat_fetch_stat_backend_by_pid() to avoid holding the
+		 * ProcArrayLock during each iteration.
+		 */
+		backend_stats = pgstat_fetch_stat_backend(local_beentry->proc_number);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3579cec5744..6a686e93fdd 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5680,6 +5680,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 2b3cf6d8569..2b4ea519677 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1860,6 +1860,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index ea7f7846895..e3f55a4c0ea 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 65d8968c83e..e6b35593a95 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--uN5gGi2rtCNSVbpC--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v4 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.7% doc/src/sgml/
   3.2% src/backend/catalog/
  23.1% src/backend/utils/adt/
   7.0% src/include/catalog/
   9.6% src/test/regress/expected/
   5.1% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..025641c2f70 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..ee3f653f360 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..fa92099e789 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..24ec3d861a2 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..ae376f96998 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..7079198bc06 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..0d6a408c7b5 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--jg9kqX3osLGO+8A7--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v4 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.7% doc/src/sgml/
   3.2% src/backend/catalog/
  23.1% src/backend/utils/adt/
   7.0% src/include/catalog/
   9.6% src/test/regress/expected/
   5.1% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..025641c2f70 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..ee3f653f360 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..fa92099e789 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..24ec3d861a2 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..ae376f96998 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..7079198bc06 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..0d6a408c7b5 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--jg9kqX3osLGO+8A7--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v4 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.7% doc/src/sgml/
   3.2% src/backend/catalog/
  23.1% src/backend/utils/adt/
   7.0% src/include/catalog/
   9.6% src/test/regress/expected/
   5.1% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..025641c2f70 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..ee3f653f360 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..fa92099e789 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..24ec3d861a2 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..ae376f96998 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..7079198bc06 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..0d6a408c7b5 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--jg9kqX3osLGO+8A7--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v4 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.7% doc/src/sgml/
   3.2% src/backend/catalog/
  23.1% src/backend/utils/adt/
   7.0% src/include/catalog/
   9.6% src/test/regress/expected/
   5.1% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..025641c2f70 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..ee3f653f360 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..fa92099e789 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..24ec3d861a2 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..ae376f96998 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..7079198bc06 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..0d6a408c7b5 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--jg9kqX3osLGO+8A7--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v4 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.7% doc/src/sgml/
   3.2% src/backend/catalog/
  23.1% src/backend/utils/adt/
   7.0% src/include/catalog/
   9.6% src/test/regress/expected/
   5.1% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..025641c2f70 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..ee3f653f360 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..fa92099e789 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..24ec3d861a2 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..ae376f96998 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..7079198bc06 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..0d6a408c7b5 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--jg9kqX3osLGO+8A7--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v5 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  65 +++++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 231 insertions(+)
  49.8% doc/src/sgml/
   3.1% src/backend/catalog/
  25.8% src/backend/utils/adt/
   6.8% src/include/catalog/
   9.2% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index bb75ed1069b..86200553293 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1195,6 +1209,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -5342,6 +5441,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index e54018004db..e005eaeb579 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -946,6 +946,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 9185a8e6b83..77ee9222ccf 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -708,6 +708,71 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns transactions statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		/* check if the backend type tracks statistics */
+		if (!pgstat_tracks_backend_bktype(beentry->st_backendType))
+			continue;
+
+		/*
+		 * Don't use pgstat_fetch_stat_backend_by_pid() to avoid holding the
+		 * ProcArrayLock during each iteration.
+		 */
+		backend_stats = pgstat_fetch_stat_backend(local_beentry->proc_number);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3579cec5744..6a686e93fdd 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5680,6 +5680,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 2b3cf6d8569..2b4ea519677 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1860,6 +1860,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index ea7f7846895..e3f55a4c0ea 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 65d8968c83e..e6b35593a95 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--uN5gGi2rtCNSVbpC--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v4 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.7% doc/src/sgml/
   3.2% src/backend/catalog/
  23.1% src/backend/utils/adt/
   7.0% src/include/catalog/
   9.6% src/test/regress/expected/
   5.1% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..025641c2f70 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..ee3f653f360 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..fa92099e789 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..24ec3d861a2 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..ae376f96998 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..7079198bc06 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..0d6a408c7b5 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--jg9kqX3osLGO+8A7--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v4 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.7% doc/src/sgml/
   3.2% src/backend/catalog/
  23.1% src/backend/utils/adt/
   7.0% src/include/catalog/
   9.6% src/test/regress/expected/
   5.1% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..025641c2f70 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..ee3f653f360 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..fa92099e789 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..24ec3d861a2 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..ae376f96998 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..7079198bc06 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..0d6a408c7b5 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--jg9kqX3osLGO+8A7--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v5 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  65 +++++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 231 insertions(+)
  49.8% doc/src/sgml/
   3.1% src/backend/catalog/
  25.8% src/backend/utils/adt/
   6.8% src/include/catalog/
   9.2% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index bb75ed1069b..86200553293 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1195,6 +1209,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -5342,6 +5441,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index e54018004db..e005eaeb579 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -946,6 +946,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 9185a8e6b83..77ee9222ccf 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -708,6 +708,71 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns transactions statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		/* check if the backend type tracks statistics */
+		if (!pgstat_tracks_backend_bktype(beentry->st_backendType))
+			continue;
+
+		/*
+		 * Don't use pgstat_fetch_stat_backend_by_pid() to avoid holding the
+		 * ProcArrayLock during each iteration.
+		 */
+		backend_stats = pgstat_fetch_stat_backend(local_beentry->proc_number);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3579cec5744..6a686e93fdd 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5680,6 +5680,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 2b3cf6d8569..2b4ea519677 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1860,6 +1860,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index ea7f7846895..e3f55a4c0ea 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 65d8968c83e..e6b35593a95 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--uN5gGi2rtCNSVbpC--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v5 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  65 +++++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 231 insertions(+)
  49.8% doc/src/sgml/
   3.1% src/backend/catalog/
  25.8% src/backend/utils/adt/
   6.8% src/include/catalog/
   9.2% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index bb75ed1069b..86200553293 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1195,6 +1209,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -5342,6 +5441,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index e54018004db..e005eaeb579 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -946,6 +946,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 9185a8e6b83..77ee9222ccf 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -708,6 +708,71 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns transactions statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		/* check if the backend type tracks statistics */
+		if (!pgstat_tracks_backend_bktype(beentry->st_backendType))
+			continue;
+
+		/*
+		 * Don't use pgstat_fetch_stat_backend_by_pid() to avoid holding the
+		 * ProcArrayLock during each iteration.
+		 */
+		backend_stats = pgstat_fetch_stat_backend(local_beentry->proc_number);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3579cec5744..6a686e93fdd 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5680,6 +5680,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 2b3cf6d8569..2b4ea519677 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1860,6 +1860,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index ea7f7846895..e3f55a4c0ea 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 65d8968c83e..e6b35593a95 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--uN5gGi2rtCNSVbpC--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v4 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.7% doc/src/sgml/
   3.2% src/backend/catalog/
  23.1% src/backend/utils/adt/
   7.0% src/include/catalog/
   9.6% src/test/regress/expected/
   5.1% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..025641c2f70 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..ee3f653f360 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..fa92099e789 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..24ec3d861a2 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..ae376f96998 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..7079198bc06 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..0d6a408c7b5 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--jg9kqX3osLGO+8A7--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v4 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.7% doc/src/sgml/
   3.2% src/backend/catalog/
  23.1% src/backend/utils/adt/
   7.0% src/include/catalog/
   9.6% src/test/regress/expected/
   5.1% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..025641c2f70 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..ee3f653f360 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..fa92099e789 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..24ec3d861a2 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..ae376f96998 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..7079198bc06 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..0d6a408c7b5 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--jg9kqX3osLGO+8A7--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread

* [PATCH v5 3/3] Adding the pg_stat_backend_transaction view
@ 2025-08-09 14:22 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 647+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing transaction statistics
related to the current activity of that process. It currently displays the pid,
the number of XIDs generated, the number of commits, the number of rollbacks and
the time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_transactions()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  65 +++++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 231 insertions(+)
  49.8% doc/src/sgml/
   3.1% src/backend/catalog/
  25.8% src/backend/utils/adt/
   6.8% src/include/catalog/
   9.2% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index bb75ed1069b..86200553293 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend_transaction</structname>
+       <indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-transaction-view">
+       <structname>pg_stat_backend_transaction</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1195,6 +1209,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-transaction-view">
+  <title><structname>pg_stat_backend_transaction</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend_transaction</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend_transaction</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
+   <title><structname>pg_stat_backend_transaction</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+       </para>
+       <para>
+        Time at which these statistics were last reset
+       </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -5342,6 +5441,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_transactions</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of transaction statistics about the backend with the
+        specified process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend_transaction</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index e54018004db..e005eaeb579 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -946,6 +946,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend_transaction AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_transactions(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 9185a8e6b83..77ee9222ccf 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -708,6 +708,71 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns transactions statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		/* check if the backend type tracks statistics */
+		if (!pgstat_tracks_backend_bktype(beentry->st_backendType))
+			continue;
+
+		/*
+		 * Don't use pgstat_fetch_stat_backend_by_pid() to avoid holding the
+		 * ProcArrayLock during each iteration.
+		 */
+		backend_stats = pgstat_fetch_stat_backend(local_beentry->proc_number);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3579cec5744..6a686e93fdd 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5680,6 +5680,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_transactions' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 2b3cf6d8569..2b4ea519677 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1860,6 +1860,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend_transaction| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index ea7f7846895..e3f55a4c0ea 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 65d8968c83e..e6b35593a95 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--uN5gGi2rtCNSVbpC--





^ permalink  raw  reply  [nested|flat] 647+ messages in thread