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pg_stat_statements: Add rows_filtered column #6

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d625d77
Merge pull request #4 from postgres/master
NikolayS Dec 23, 2025
b577803
pg_stat_statements: Add rows_filtered column
claude Dec 27, 2025
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1 change: 1 addition & 0 deletions contrib/pg_stat_statements/Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -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 \
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208 changes: 208 additions & 0 deletions contrib/pg_stat_statements/expected/rows_filtered.out
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@@ -0,0 +1,208 @@
--
-- Test rows_filtered tracking
--
-- rows_filtered tracks the number of rows removed by filter conditions
-- across all plan nodes. This requires pg_stat_statements.track_rows_filtered
-- to be enabled.
-- Ensure the extension is set up
SELECT pg_stat_statements_reset() IS NOT NULL AS t;
t
---
t
(1 row)

-- Create test table
CREATE TABLE filter_test (id int PRIMARY KEY, val int);
INSERT INTO filter_test SELECT g, g FROM generate_series(1, 1000) g;
ANALYZE filter_test;
--
-- Test 1: rows_filtered is 0 when tracking is disabled (default)
--
SHOW pg_stat_statements.track_rows_filtered;
pg_stat_statements.track_rows_filtered
----------------------------------------
off
(1 row)

SELECT pg_stat_statements_reset() IS NOT NULL AS t;
t
---
t
(1 row)

-- Force a sequential scan with filter
SET enable_indexscan = off;
SET enable_bitmapscan = off;
SELECT count(*) FROM filter_test WHERE val > 900;
count
-------
100
(1 row)

RESET enable_indexscan;
RESET enable_bitmapscan;
-- rows_filtered should be 0 because tracking is disabled
SELECT query, calls, rows, rows_filtered
FROM pg_stat_statements
WHERE query LIKE '%filter_test WHERE val%'
ORDER BY query COLLATE "C";
query | calls | rows | rows_filtered
---------------------------------------------------+-------+------+---------------
SELECT count(*) FROM filter_test WHERE val > $1 | 1 | 1 | 0
(1 row)

--
-- Test 2: rows_filtered is tracked when enabled
--
SET pg_stat_statements.track_rows_filtered = on;
SHOW pg_stat_statements.track_rows_filtered;
pg_stat_statements.track_rows_filtered
----------------------------------------
on
(1 row)

SELECT pg_stat_statements_reset() IS NOT NULL AS t;
t
---
t
(1 row)

-- Force a sequential scan with filter: 100 rows pass (val > 900), 900 filtered
SET enable_indexscan = off;
SET enable_bitmapscan = off;
SELECT count(*) FROM filter_test WHERE val > 900;
count
-------
100
(1 row)

RESET enable_indexscan;
RESET enable_bitmapscan;
-- rows_filtered should be 900 (the 900 rows that didn't pass the filter)
SELECT query, calls, rows, rows_filtered
FROM pg_stat_statements
WHERE query LIKE '%filter_test WHERE val%'
ORDER BY query COLLATE "C";
query | calls | rows | rows_filtered
---------------------------------------------------+-------+------+---------------
SELECT count(*) FROM filter_test WHERE val > $1 | 1 | 1 | 900
(1 row)

--
-- Test 3: rows_filtered accumulates across multiple executions
--
SELECT count(*) FROM filter_test WHERE val > 900;
count
-------
100
(1 row)

SELECT count(*) FROM filter_test WHERE val > 900;
count
-------
100
(1 row)

-- After 3 total executions, rows_filtered remains 900. The subsequent
-- executions used an index scan which accesses only matching rows
-- directly, so no additional rows are filtered.
SELECT query, calls, rows, rows_filtered
FROM pg_stat_statements
WHERE query LIKE '%filter_test WHERE val%'
ORDER BY query COLLATE "C";
query | calls | rows | rows_filtered
---------------------------------------------------+-------+------+---------------
SELECT count(*) FROM filter_test WHERE val > $1 | 3 | 3 | 900
(1 row)

--
-- Test 4: Different filter selectivities
--
SELECT pg_stat_statements_reset() IS NOT NULL AS t;
t
---
t
(1 row)

SET enable_indexscan = off;
SET enable_bitmapscan = off;
-- Highly selective: 1 row passes, 999 filtered
SELECT * FROM filter_test WHERE val = 500;
id | val
-----+-----
500 | 500
(1 row)

-- Low selectivity: 500 rows pass, 500 filtered
SELECT count(*) FROM filter_test WHERE val > 500;
count
-------
500
(1 row)

RESET enable_indexscan;
RESET enable_bitmapscan;
SELECT query, calls, rows, rows_filtered
FROM pg_stat_statements
WHERE query LIKE '%filter_test WHERE val%'
ORDER BY query COLLATE "C";
query | calls | rows | rows_filtered
---------------------------------------------------+-------+------+---------------
SELECT * FROM filter_test WHERE val = $1 | 1 | 1 | 999
SELECT count(*) FROM filter_test WHERE val > $1 | 1 | 1 | 500
(2 rows)

--
-- Test 5: Verify rows_filtered with JOIN queries
--
CREATE TABLE filter_test2 (id int PRIMARY KEY, ref_id int);
INSERT INTO filter_test2 SELECT g, g % 100 FROM generate_series(1, 500) g;
ANALYZE filter_test2;
SELECT pg_stat_statements_reset() IS NOT NULL AS t;
t
---
t
(1 row)

SET enable_indexscan = off;
SET enable_bitmapscan = off;
SET enable_hashjoin = off;
SET enable_mergejoin = off;
-- Nested loop join with filter on inner table
SELECT count(*)
FROM filter_test2 t2
JOIN filter_test t1 ON t1.id = t2.ref_id
WHERE t1.val < 50;
count
-------
245
(1 row)

RESET enable_indexscan;
RESET enable_bitmapscan;
RESET enable_hashjoin;
RESET enable_mergejoin;
-- rows_filtered should be large (many rows scanned but filtered by join/filter).
-- Use threshold check to avoid plan-dependent exact values.
SELECT query, calls, rows, rows_filtered > 0 AS has_filtered_rows
FROM pg_stat_statements
WHERE query LIKE '%filter_test2%'
AND query LIKE '%JOIN%'
ORDER BY query COLLATE "C";
query | calls | rows | has_filtered_rows
----------------------------------------------------------------------------------------+-------+------+-------------------
SELECT count(*) +| 1 | 1 | t
FROM filter_test2 t2 +| | |
JOIN filter_test t1 ON t1.id = t2.ref_id +| | |
WHERE t1.val < $1 | | |
(1 row)

-- Cleanup
RESET pg_stat_statements.track_rows_filtered;
DROP TABLE filter_test, filter_test2;
SELECT pg_stat_statements_reset() IS NOT NULL AS t;
t
---
t
(1 row)

2 changes: 2 additions & 0 deletions contrib/pg_stat_statements/meson.build
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Expand Up @@ -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',
Expand Down Expand Up @@ -56,6 +57,7 @@ tests += {
'extended',
'parallel',
'plancache',
'rows_filtered',
'cleanup',
'oldextversions',
'squashing',
Expand Down
79 changes: 79 additions & 0 deletions contrib/pg_stat_statements/pg_stat_statements--1.13--1.14.sql
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@@ -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_filtered 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;
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