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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
160 lines
4.5 KiB
Plaintext
160 lines
4.5 KiB
Plaintext
--
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-- statement timestamps
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--
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-- planning time is needed during tests
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SET pg_stat_statements.track_planning = TRUE;
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SELECT 1 AS "STMTTS1";
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STMTTS1
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---------
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1
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(1 row)
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SELECT now() AS ref_ts \gset
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SELECT 1,2 AS "STMTTS2";
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?column? | STMTTS2
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----------+---------
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1 | 2
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(1 row)
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SELECT stats_since >= :'ref_ts', count(*) FROM pg_stat_statements
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WHERE query LIKE '%STMTTS%'
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GROUP BY stats_since >= :'ref_ts'
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ORDER BY stats_since >= :'ref_ts';
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?column? | count
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----------+-------
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f | 1
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t | 1
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(2 rows)
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SELECT now() AS ref_ts \gset
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SELECT
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count(*) as total,
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count(*) FILTER (
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WHERE min_plan_time + max_plan_time = 0
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) as minmax_plan_zero,
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count(*) FILTER (
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WHERE min_exec_time + max_exec_time = 0
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) as minmax_exec_zero,
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count(*) FILTER (
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WHERE minmax_stats_since >= :'ref_ts'
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) as minmax_stats_since_after_ref,
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count(*) FILTER (
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WHERE stats_since >= :'ref_ts'
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) as stats_since_after_ref
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FROM pg_stat_statements
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WHERE query LIKE '%STMTTS%';
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total | minmax_plan_zero | minmax_exec_zero | minmax_stats_since_after_ref | stats_since_after_ref
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-------+------------------+------------------+------------------------------+-----------------------
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2 | 0 | 0 | 0 | 0
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(1 row)
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-- Perform single min/max reset
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SELECT pg_stat_statements_reset(0, 0, queryid, true) AS minmax_reset_ts
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FROM pg_stat_statements
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WHERE query LIKE '%STMTTS1%' \gset
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-- check
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SELECT
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count(*) as total,
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count(*) FILTER (
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WHERE min_plan_time + max_plan_time = 0
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) as minmax_plan_zero,
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count(*) FILTER (
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WHERE min_exec_time + max_exec_time = 0
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) as minmax_exec_zero,
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count(*) FILTER (
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WHERE minmax_stats_since >= :'ref_ts'
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) as minmax_stats_since_after_ref,
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count(*) FILTER (
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WHERE stats_since >= :'ref_ts'
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) as stats_since_after_ref
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FROM pg_stat_statements
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WHERE query LIKE '%STMTTS%';
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total | minmax_plan_zero | minmax_exec_zero | minmax_stats_since_after_ref | stats_since_after_ref
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-------+------------------+------------------+------------------------------+-----------------------
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2 | 1 | 1 | 1 | 0
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(1 row)
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-- check minmax reset timestamps
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SELECT
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query, minmax_stats_since = :'minmax_reset_ts' AS reset_ts_match
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FROM pg_stat_statements
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WHERE query LIKE '%STMTTS%'
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ORDER BY query COLLATE "C";
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query | reset_ts_match
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---------------------------+----------------
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SELECT $1 AS "STMTTS1" | t
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SELECT $1,$2 AS "STMTTS2" | f
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(2 rows)
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-- check that minmax reset does not set stats_reset
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SELECT
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stats_reset = :'minmax_reset_ts' AS stats_reset_ts_match
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FROM pg_stat_statements_info;
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stats_reset_ts_match
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----------------------
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f
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(1 row)
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-- Perform common min/max reset
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SELECT pg_stat_statements_reset(0, 0, 0, true) AS minmax_reset_ts \gset
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-- check again
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SELECT
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count(*) as total,
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count(*) FILTER (
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WHERE min_plan_time + max_plan_time = 0
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) as minmax_plan_zero,
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count(*) FILTER (
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WHERE min_exec_time + max_exec_time = 0
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) as minmax_exec_zero,
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count(*) FILTER (
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WHERE minmax_stats_since >= :'ref_ts'
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) as minmax_ts_after_ref,
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count(*) FILTER (
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WHERE minmax_stats_since = :'minmax_reset_ts'
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) as minmax_ts_match,
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count(*) FILTER (
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WHERE stats_since >= :'ref_ts'
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) as stats_since_after_ref
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FROM pg_stat_statements
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WHERE query LIKE '%STMTTS%';
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total | minmax_plan_zero | minmax_exec_zero | minmax_ts_after_ref | minmax_ts_match | stats_since_after_ref
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-------+------------------+------------------+---------------------+-----------------+-----------------------
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2 | 2 | 2 | 2 | 2 | 0
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(1 row)
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-- Execute first query once more to check stats update
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SELECT 1 AS "STMTTS1";
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STMTTS1
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---------
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1
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(1 row)
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-- check
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-- we don't check planing times here to be independent of
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-- plan caching approach
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SELECT
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count(*) as total,
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count(*) FILTER (
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WHERE min_exec_time + max_exec_time = 0
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) as minmax_exec_zero,
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count(*) FILTER (
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WHERE minmax_stats_since >= :'ref_ts'
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) as minmax_ts_after_ref,
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count(*) FILTER (
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WHERE stats_since >= :'ref_ts'
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) as stats_since_after_ref
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FROM pg_stat_statements
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WHERE query LIKE '%STMTTS%';
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total | minmax_exec_zero | minmax_ts_after_ref | stats_since_after_ref
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-------+------------------+---------------------+-----------------------
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2 | 1 | 2 | 0
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(1 row)
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-- Cleanup
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SELECT pg_stat_statements_reset() IS NOT NULL AS t;
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t
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---
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t
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(1 row)
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