pg_stat_statements: Add rows_scanned column

Add a new rows_scanned column to pg_stat_statements that tracks the
total number of rows scanned by scan nodes (SeqScan, IndexScan,
IndexOnlyScan, BitmapHeapScan, etc.) before filter conditions are
applied. This metric is collected by walking the plan tree and summing
up ntuples + nfiltered1 for all scan nodes.

This information is valuable for identifying queries that scan many
rows but return few, which often indicates missing indexes or
suboptimal query plans. Combined with the existing rows column, users
can calculate the filtering efficiency of their queries.

The new column appears after rows in the view, so existing queries
that select specific columns by name will continue to work. Bump
extension version to 1.14.

Author: claude

contrib/pg_stat_statements/Makefile

@@ -7,6 +7,7 @@ OBJS = \
 
 EXTENSION = pg_stat_statements
 DATA = pg_stat_statements--1.4.sql \
+	pg_stat_statements--1.13--1.14.sql \
 	pg_stat_statements--1.12--1.13.sql \
 	pg_stat_statements--1.11--1.12.sql pg_stat_statements--1.10--1.11.sql \
 	pg_stat_statements--1.9--1.10.sql pg_stat_statements--1.8--1.9.sql \

contrib/pg_stat_statements/meson.build

@@ -21,6 +21,7 @@ contrib_targets += pg_stat_statements
 install_data(
   'pg_stat_statements.control',
   'pg_stat_statements--1.4.sql',
+  'pg_stat_statements--1.13--1.14.sql',
   'pg_stat_statements--1.12--1.13.sql',
   'pg_stat_statements--1.11--1.12.sql',
   'pg_stat_statements--1.10--1.11.sql',

contrib/pg_stat_statements/pg_stat_statements--1.13--1.14.sql

@@ -0,0 +1,79 @@
+/* contrib/pg_stat_statements/pg_stat_statements--1.13--1.14.sql */
+
+-- complain if script is sourced in psql, rather than via ALTER EXTENSION
+\echo Use "ALTER EXTENSION pg_stat_statements UPDATE TO '1.14'" to load this file. \quit
+
+/* First we have to remove them from the extension */
+ALTER EXTENSION pg_stat_statements DROP VIEW pg_stat_statements;
+ALTER EXTENSION pg_stat_statements DROP FUNCTION pg_stat_statements(boolean);
+
+/* Then we can drop them */
+DROP VIEW pg_stat_statements;
+DROP FUNCTION pg_stat_statements(boolean);
+
+/* Now redefine */
+CREATE FUNCTION pg_stat_statements(IN showtext boolean,
+    OUT userid oid,
+    OUT dbid oid,
+    OUT toplevel bool,
+    OUT queryid bigint,
+    OUT query text,
+    OUT plans int8,
+    OUT total_plan_time float8,
+    OUT min_plan_time float8,
+    OUT max_plan_time float8,
+    OUT mean_plan_time float8,
+    OUT stddev_plan_time float8,
+    OUT calls int8,
+    OUT total_exec_time float8,
+    OUT min_exec_time float8,
+    OUT max_exec_time float8,
+    OUT mean_exec_time float8,
+    OUT stddev_exec_time float8,
+    OUT rows int8,
+    OUT rows_scanned int8,
+    OUT shared_blks_hit int8,
+    OUT shared_blks_read int8,
+    OUT shared_blks_dirtied int8,
+    OUT shared_blks_written int8,
+    OUT local_blks_hit int8,
+    OUT local_blks_read int8,
+    OUT local_blks_dirtied int8,
+    OUT local_blks_written int8,
+    OUT temp_blks_read int8,
+    OUT temp_blks_written int8,
+    OUT shared_blk_read_time float8,
+    OUT shared_blk_write_time float8,
+    OUT local_blk_read_time float8,
+    OUT local_blk_write_time float8,
+    OUT temp_blk_read_time float8,
+    OUT temp_blk_write_time float8,
+    OUT wal_records int8,
+    OUT wal_fpi int8,
+    OUT wal_bytes numeric,
+    OUT wal_buffers_full int8,
+    OUT jit_functions int8,
+    OUT jit_generation_time float8,
+    OUT jit_inlining_count int8,
+    OUT jit_inlining_time float8,
+    OUT jit_optimization_count int8,
+    OUT jit_optimization_time float8,
+    OUT jit_emission_count int8,
+    OUT jit_emission_time float8,
+    OUT jit_deform_count int8,
+    OUT jit_deform_time float8,
+    OUT parallel_workers_to_launch int8,
+    OUT parallel_workers_launched int8,
+    OUT generic_plan_calls int8,
+    OUT custom_plan_calls int8,
+    OUT stats_since timestamp with time zone,
+    OUT minmax_stats_since timestamp with time zone
+)
+RETURNS SETOF record
+AS 'MODULE_PATHNAME', 'pg_stat_statements_1_14'
+LANGUAGE C STRICT VOLATILE PARALLEL SAFE;
+
+CREATE VIEW pg_stat_statements AS
+  SELECT * FROM pg_stat_statements(true);
+
+GRANT SELECT ON pg_stat_statements TO PUBLIC;

contrib/pg_stat_statements/pg_stat_statements.c

@@ -56,6 +56,7 @@
 #include "jit/jit.h"
 #include "mb/pg_wchar.h"
 #include "miscadmin.h"
+#include "nodes/nodeFuncs.h"
 #include "nodes/queryjumble.h"
 #include "optimizer/planner.h"
 #include "parser/analyze.h"
@@ -116,6 +117,7 @@ typedef enum pgssVersion
 	PGSS_V1_11,
 	PGSS_V1_12,
 	PGSS_V1_13,
+	PGSS_V1_14,
 } pgssVersion;
 
 typedef enum pgssStoreKind
@@ -166,6 +168,7 @@ typedef struct Counters
 	double		sum_var_time[PGSS_NUMKIND]; /* sum of variances in
 											 * planning/execution time in msec */
 	int64		rows;			/* total # of retrieved or affected rows */
+	int64		rows_scanned;	/* total # of rows scanned by scan nodes */
 	int64		shared_blks_hit;	/* # of shared buffer hits */
 	int64		shared_blks_read;	/* # of shared disk blocks read */
 	int64		shared_blks_dirtied;	/* # of shared disk blocks dirtied */
@@ -327,6 +330,7 @@ PG_FUNCTION_INFO_V1(pg_stat_statements_1_10);
 PG_FUNCTION_INFO_V1(pg_stat_statements_1_11);
 PG_FUNCTION_INFO_V1(pg_stat_statements_1_12);
 PG_FUNCTION_INFO_V1(pg_stat_statements_1_13);
+PG_FUNCTION_INFO_V1(pg_stat_statements_1_14);
 PG_FUNCTION_INFO_V1(pg_stat_statements);
 PG_FUNCTION_INFO_V1(pg_stat_statements_info);
 
@@ -355,6 +359,7 @@ static void pgss_store(const char *query, int64 queryId,
 					   int query_location, int query_len,
 					   pgssStoreKind kind,
 					   double total_time, uint64 rows,
+					   int64 rows_scanned,
 					   const BufferUsage *bufusage,
 					   const WalUsage *walusage,
 					   const struct JitInstrumentation *jitusage,
@@ -878,6 +883,7 @@ pgss_post_parse_analyze(ParseState *pstate, Query *query, JumbleState *jstate)
 				   PGSS_INVALID,
 				   0,
 				   0,
+				   0,
 				   NULL,
 				   NULL,
 				   NULL,
@@ -960,6 +966,7 @@ pgss_planner(Query *parse,
 				   PGSS_PLAN,
 				   INSTR_TIME_GET_MILLISEC(duration),
 				   0,
+				   0,
 				   &bufusage,
 				   &walusage,
 				   NULL,
@@ -1071,6 +1078,74 @@ pgss_ExecutorFinish(QueryDesc *queryDesc)
 	PG_END_TRY();
 }
 
+/*
+ * Helper structure for collecting scan statistics
+ */
+typedef struct ScanStats
+{
+	int64		rows_scanned;	/* total rows scanned (before filtering) */
+} ScanStats;
+
+/*
+ * Determine if a node is a scan node that reads from storage.
+ * For scan nodes, we want to count tuples before filter conditions are applied.
+ */
+static inline bool
+IsScanNode(PlanState *planstate)
+{
+	switch (nodeTag(planstate))
+	{
+		case T_SeqScanState:
+		case T_SampleScanState:
+		case T_IndexScanState:
+		case T_IndexOnlyScanState:
+		case T_BitmapHeapScanState:
+		case T_TidScanState:
+		case T_TidRangeScanState:
+		case T_ForeignScanState:
+		case T_CustomScanState:
+			return true;
+		default:
+			return false;
+	}
+}
+
+/*
+ * Walker function to collect scan statistics from all nodes.
+ * For scan nodes, rows_scanned = tuples output + tuples filtered.
+ */
+static bool
+pgss_collect_scan_stats_walker(PlanState *planstate, void *context)
+{
+	ScanStats  *stats = (ScanStats *) context;
+
+	if (planstate->instrument && IsScanNode(planstate))
+	{
+		/*
+		 * For scan nodes, rows_scanned is the number of tuples produced plus
+		 * the number of tuples filtered out by the scan's filter condition.
+		 * This represents the total number of tuples read from storage.
+		 */
+		double		scanned = planstate->instrument->ntuples +
+							  planstate->instrument->nfiltered1;
+
+		stats->rows_scanned += (int64) scanned;
+	}
+
+	return planstate_tree_walker(planstate, pgss_collect_scan_stats_walker, context);
+}
+
+/*
+ * Collect scan statistics from the entire plan tree.
+ */
+static void
+pgss_collect_scan_stats(PlanState *planstate, ScanStats *stats)
+{
+	memset(stats, 0, sizeof(ScanStats));
+	if (planstate)
+		pgss_collect_scan_stats_walker(planstate, stats);
+}
+
 /*
  * ExecutorEnd hook: store results if needed
  */
@@ -1082,19 +1157,28 @@ pgss_ExecutorEnd(QueryDesc *queryDesc)
 	if (queryId != INT64CONST(0) && queryDesc->totaltime &&
 		pgss_enabled(nesting_level))
 	{
+		ScanStats	scan_stats;
+
 		/*
 		 * Make sure stats accumulation is done.  (Note: it's okay if several
 		 * levels of hook all do this.)
 		 */
 		InstrEndLoop(queryDesc->totaltime);
 
+		/*
+		 * Collect scan statistics from the plan tree.  This must be done
+		 * before standard_ExecutorEnd which will destroy the planstate.
+		 */
+		pgss_collect_scan_stats(queryDesc->planstate, &scan_stats);
+
 		pgss_store(queryDesc->sourceText,
 				   queryId,
 				   queryDesc->plannedstmt->stmt_location,
 				   queryDesc->plannedstmt->stmt_len,
 				   PGSS_EXEC,
 				   queryDesc->totaltime->total * 1000.0,	/* convert to msec */
 				   queryDesc->estate->es_total_processed,
+				   scan_stats.rows_scanned,
 				   &queryDesc->totaltime->bufusage,
 				   &queryDesc->totaltime->walusage,
 				   queryDesc->estate->es_jit ? &queryDesc->estate->es_jit->instr : NULL,
@@ -1229,6 +1313,7 @@ pgss_ProcessUtility(PlannedStmt *pstmt, const char *queryString,
 				   PGSS_EXEC,
 				   INSTR_TIME_GET_MILLISEC(duration),
 				   rows,
+				   0,	/* rows_scanned not available for utility statements */
 				   &bufusage,
 				   &walusage,
 				   NULL,
@@ -1293,6 +1378,7 @@ pgss_store(const char *query, int64 queryId,
 		   int query_location, int query_len,
 		   pgssStoreKind kind,
 		   double total_time, uint64 rows,
+		   int64 rows_scanned,
 		   const BufferUsage *bufusage,
 		   const WalUsage *walusage,
 		   const struct JitInstrumentation *jitusage,
@@ -1460,6 +1546,7 @@ pgss_store(const char *query, int64 queryId,
 			}
 		}
 		entry->counters.rows += rows;
+		entry->counters.rows_scanned += rows_scanned;
 		entry->counters.shared_blks_hit += bufusage->shared_blks_hit;
 		entry->counters.shared_blks_read += bufusage->shared_blks_read;
 		entry->counters.shared_blks_dirtied += bufusage->shared_blks_dirtied;
@@ -1581,7 +1668,8 @@ pg_stat_statements_reset(PG_FUNCTION_ARGS)
 #define PG_STAT_STATEMENTS_COLS_V1_11	49
 #define PG_STAT_STATEMENTS_COLS_V1_12	52
 #define PG_STAT_STATEMENTS_COLS_V1_13	54
-#define PG_STAT_STATEMENTS_COLS			54	/* maximum of above */
+#define PG_STAT_STATEMENTS_COLS_V1_14	55
+#define PG_STAT_STATEMENTS_COLS			55	/* maximum of above */
 
 /*
  * Retrieve statement statistics.
@@ -1593,6 +1681,16 @@ pg_stat_statements_reset(PG_FUNCTION_ARGS)
  * expected API version is identified by embedding it in the C name of the
  * function.  Unfortunately we weren't bright enough to do that for 1.1.
  */
+Datum
+pg_stat_statements_1_14(PG_FUNCTION_ARGS)
+{
+	bool		showtext = PG_GETARG_BOOL(0);
+
+	pg_stat_statements_internal(fcinfo, PGSS_V1_14, showtext);
+
+	return (Datum) 0;
+}
+
 Datum
 pg_stat_statements_1_13(PG_FUNCTION_ARGS)
 {
@@ -1765,6 +1863,10 @@ pg_stat_statements_internal(FunctionCallInfo fcinfo,
 			if (api_version != PGSS_V1_13)
 				elog(ERROR, "incorrect number of output arguments");
 			break;
+		case PG_STAT_STATEMENTS_COLS_V1_14:
+			if (api_version != PGSS_V1_14)
+				elog(ERROR, "incorrect number of output arguments");
+			break;
 		default:
 			elog(ERROR, "incorrect number of output arguments");
 	}
@@ -1948,6 +2050,8 @@ pg_stat_statements_internal(FunctionCallInfo fcinfo,
 			}
 		}
 		values[i++] = Int64GetDatumFast(tmp.rows);
+		if (api_version >= PGSS_V1_14)
+			values[i++] = Int64GetDatumFast(tmp.rows_scanned);
 		values[i++] = Int64GetDatumFast(tmp.shared_blks_hit);
 		values[i++] = Int64GetDatumFast(tmp.shared_blks_read);
 		if (api_version >= PGSS_V1_1)
@@ -2038,6 +2142,7 @@ pg_stat_statements_internal(FunctionCallInfo fcinfo,
 					 api_version == PGSS_V1_11 ? PG_STAT_STATEMENTS_COLS_V1_11 :
 					 api_version == PGSS_V1_12 ? PG_STAT_STATEMENTS_COLS_V1_12 :
 					 api_version == PGSS_V1_13 ? PG_STAT_STATEMENTS_COLS_V1_13 :
+					 api_version == PGSS_V1_14 ? PG_STAT_STATEMENTS_COLS_V1_14 :
 					 -1 /* fail if you forget to update this assert */ ));
 
 		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);

contrib/pg_stat_statements/pg_stat_statements.control

@@ -1,5 +1,5 @@
 # pg_stat_statements extension
 comment = 'track planning and execution statistics of all SQL statements executed'
-default_version = '1.13'
+default_version = '1.14'
 module_pathname = '$libdir/pg_stat_statements'
 relocatable = true