postgresql/contrib/pg_stat_statements/expected/entry_timestamp.out

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Track statement entry timestamp in contrib/pg_stat_statements This patch adds 'stats_since' and 'minmax_stats_since' columns to the pg_stat_statements view and pg_stat_statements() function. The new min/max reset mode for the pg_stat_stetments_reset() function is controlled by the parameter minmax_only. 'stat_since' column is populated with the current timestamp when a new statement is added to the pg_stat_statements hashtable. It provides clean information about statistics collection time intervals for each statement. Besides it can be used by sampling solutions to detect situations when a statement was evicted and stored again between samples. Such a sampling solution could derive any pg_stat_statements statistic values for an interval between two samples with the exception of all min/max statistics. To address this issue this patch adds the ability to reset min/max statistics independently of the statement reset using the new minmax_only parameter of the pg_stat_statements_reset(userid oid, dbid oid, queryid bigint, minmax_only boolean) function. The timestamp of such reset is stored in the minmax_stats_since field for each statement. pg_stat_statements_reset() function now returns the timestamp of a reset as the result. Discussion: https://postgr.es/m/flat/72e80e7b160a6eb189df9ef6f068cce3765d37f8.camel%40moonset.ru Author: Andrei Zubkov Reviewed-by: Julien Rouhaud, Hayato Kuroda, Yuki Seino, Chengxi Sun Reviewed-by: Anton Melnikov, Darren Rush, Michael Paquier, Sergei Kornilov Reviewed-by: Alena Rybakina, Andrei Lepikhov
2023-11-27 01:51:18 +01:00
--
-- statement timestamps
--
-- planning time is needed during tests
SET pg_stat_statements.track_planning = TRUE;
SELECT 1 AS "STMTTS1";
STMTTS1
---------
1
(1 row)
SELECT now() AS ref_ts \gset
SELECT 1,2 AS "STMTTS2";
?column? | STMTTS2
----------+---------
1 | 2
(1 row)
SELECT stats_since >= :'ref_ts', count(*) FROM pg_stat_statements
WHERE query LIKE '%STMTTS%'
GROUP BY stats_since >= :'ref_ts'
ORDER BY stats_since >= :'ref_ts';
?column? | count
----------+-------
f | 1
t | 1
(2 rows)
SELECT now() AS ref_ts \gset
SELECT
count(*) as total,
count(*) FILTER (
WHERE min_plan_time + max_plan_time = 0
) as minmax_plan_zero,
count(*) FILTER (
WHERE min_exec_time + max_exec_time = 0
) as minmax_exec_zero,
count(*) FILTER (
WHERE minmax_stats_since >= :'ref_ts'
) as minmax_stats_since_after_ref,
count(*) FILTER (
WHERE stats_since >= :'ref_ts'
) as stats_since_after_ref
FROM pg_stat_statements
WHERE query LIKE '%STMTTS%';
total | minmax_plan_zero | minmax_exec_zero | minmax_stats_since_after_ref | stats_since_after_ref
-------+------------------+------------------+------------------------------+-----------------------
2 | 0 | 0 | 0 | 0
(1 row)
-- Perform single min/max reset
SELECT pg_stat_statements_reset(0, 0, queryid, true) AS minmax_reset_ts
FROM pg_stat_statements
WHERE query LIKE '%STMTTS1%' \gset
-- check
SELECT
count(*) as total,
count(*) FILTER (
WHERE min_plan_time + max_plan_time = 0
) as minmax_plan_zero,
count(*) FILTER (
WHERE min_exec_time + max_exec_time = 0
) as minmax_exec_zero,
count(*) FILTER (
WHERE minmax_stats_since >= :'ref_ts'
) as minmax_stats_since_after_ref,
count(*) FILTER (
WHERE stats_since >= :'ref_ts'
) as stats_since_after_ref
FROM pg_stat_statements
WHERE query LIKE '%STMTTS%';
total | minmax_plan_zero | minmax_exec_zero | minmax_stats_since_after_ref | stats_since_after_ref
-------+------------------+------------------+------------------------------+-----------------------
2 | 1 | 1 | 1 | 0
(1 row)
-- check minmax reset timestamps
SELECT
query, minmax_stats_since = :'minmax_reset_ts' AS reset_ts_match
FROM pg_stat_statements
WHERE query LIKE '%STMTTS%'
ORDER BY query COLLATE "C";
query | reset_ts_match
---------------------------+----------------
SELECT $1 AS "STMTTS1" | t
SELECT $1,$2 AS "STMTTS2" | f
(2 rows)
-- check that minmax reset does not set stats_reset
SELECT
stats_reset = :'minmax_reset_ts' AS stats_reset_ts_match
FROM pg_stat_statements_info;
stats_reset_ts_match
----------------------
f
(1 row)
-- Perform common min/max reset
SELECT pg_stat_statements_reset(0, 0, 0, true) AS minmax_reset_ts \gset
-- check again
SELECT
count(*) as total,
count(*) FILTER (
WHERE min_plan_time + max_plan_time = 0
) as minmax_plan_zero,
count(*) FILTER (
WHERE min_exec_time + max_exec_time = 0
) as minmax_exec_zero,
count(*) FILTER (
WHERE minmax_stats_since >= :'ref_ts'
) as minmax_ts_after_ref,
count(*) FILTER (
WHERE minmax_stats_since = :'minmax_reset_ts'
) as minmax_ts_match,
count(*) FILTER (
WHERE stats_since >= :'ref_ts'
) as stats_since_after_ref
FROM pg_stat_statements
WHERE query LIKE '%STMTTS%';
total | minmax_plan_zero | minmax_exec_zero | minmax_ts_after_ref | minmax_ts_match | stats_since_after_ref
-------+------------------+------------------+---------------------+-----------------+-----------------------
2 | 2 | 2 | 2 | 2 | 0
(1 row)
-- Execute first query once more to check stats update
SELECT 1 AS "STMTTS1";
STMTTS1
---------
1
(1 row)
-- check
-- we don't check planing times here to be independent of
-- plan caching approach
SELECT
count(*) as total,
count(*) FILTER (
WHERE min_exec_time + max_exec_time = 0
) as minmax_exec_zero,
count(*) FILTER (
WHERE minmax_stats_since >= :'ref_ts'
) as minmax_ts_after_ref,
count(*) FILTER (
WHERE stats_since >= :'ref_ts'
) as stats_since_after_ref
FROM pg_stat_statements
WHERE query LIKE '%STMTTS%';
total | minmax_exec_zero | minmax_ts_after_ref | stats_since_after_ref
-------+------------------+---------------------+-----------------------
2 | 1 | 2 | 0
(1 row)
-- Cleanup
SELECT pg_stat_statements_reset() IS NOT NULL AS t;
t
---
t
(1 row)