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Fix some issues with tracking nesting level in pg_stat_statements.

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When we decide that we don't want to track execution time of a
specific planner or ProcessUtility call, we still have to increment
the nesting depth, or we'll make the wrong determination of whether
we are at top level when considering nested statements.  (PREPARE
and EXECUTE are exceptions, for reasons explained in the code.)

Counting planner nesting depth separately from executor nesting depth
was a mistake: it causes us to make the wrong determination of whether
we are at top level when considering nested statements that get
executed during planning (as a result of constant-folding of
functions, for example).  Merge those counters into one.

In passing, get rid of the PGSS_HANDLED_UTILITY macro in favor of
explicitly listing statement types.  It seems somewhat coincidental
that PREPARE and EXECUTE are handled alike in each of the places where
that was used: the reasoning tends to be different for each one.
Thus, the macro seems as likely to encourage future bugs as prevent
them, since it's quite unclear whether any future statement type that
might need special-casing here would also need the same choices at
each spot.

Sergei Kornilov, Julien Rouhaud, and Tom Lane, per bug #17552 from
Maxim Boguk.  This is pretty clearly a bug fix, but it's also a
behavioral change that might surprise somebody, so no back-patch.

Discussion: https://postgr.es/m/17552-213b534c56ab5d02@postgresql.org
This commit is contained in:
Tom Lane
2023-11-08 12:01:28 -05:00
parent 1a5594b957
commit 76db9cb636
3 changed files with 242 additions and 47 deletions
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53
contrib/pg_stat_statements/sql/level_tracking.sql
View File

@ -33,6 +33,39 @@ END; $$;
SELECT toplevel, calls, query FROM pg_stat_statements
ORDER BY query COLLATE "C", toplevel;
-- DO block - top-level tracking without utility.
SET pg_stat_statements.track = 'top';
SET pg_stat_statements.track_utility = FALSE;
SELECT pg_stat_statements_reset();
DELETE FROM stats_track_tab;
DO $$
BEGIN
DELETE FROM stats_track_tab;
END; $$;
DO LANGUAGE plpgsql $$
BEGIN
-- this is a SELECT
PERFORM 'hello world'::TEXT;
END; $$;
SELECT toplevel, calls, query FROM pg_stat_statements
ORDER BY query COLLATE "C", toplevel;
-- DO block - all-level tracking without utility.
SET pg_stat_statements.track = 'all';
SELECT pg_stat_statements_reset();
DELETE FROM stats_track_tab;
DO $$
BEGIN
DELETE FROM stats_track_tab;
END; $$;
DO LANGUAGE plpgsql $$
BEGIN
-- this is a SELECT
PERFORM 'hello world'::TEXT;
END; $$;
SELECT toplevel, calls, query FROM pg_stat_statements
ORDER BY query COLLATE "C", toplevel;
-- PL/pgSQL function - top-level tracking.
SET pg_stat_statements.track = 'top';
SET pg_stat_statements.track_utility = FALSE;
@ -57,6 +90,15 @@ SELECT PLUS_ONE(10);
SELECT calls, rows, query FROM pg_stat_statements ORDER BY query COLLATE "C";
-- immutable SQL function --- can be executed at plan time
CREATE FUNCTION PLUS_THREE(i INTEGER) RETURNS INTEGER AS
$$ SELECT i + 3 LIMIT 1 $$ IMMUTABLE LANGUAGE SQL;
SELECT PLUS_THREE(8);
SELECT PLUS_THREE(10);
SELECT toplevel, calls, rows, query FROM pg_stat_statements ORDER BY query COLLATE "C";
-- PL/pgSQL function - all-level tracking.
SET pg_stat_statements.track = 'all';
SELECT pg_stat_statements_reset();
@ -64,6 +106,7 @@ SELECT pg_stat_statements_reset();
-- we drop and recreate the functions to avoid any caching funnies
DROP FUNCTION PLUS_ONE(INTEGER);
DROP FUNCTION PLUS_TWO(INTEGER);
DROP FUNCTION PLUS_THREE(INTEGER);
-- PL/pgSQL function
CREATE FUNCTION PLUS_TWO(i INTEGER) RETURNS INTEGER AS $$
@ -85,7 +128,15 @@ SELECT PLUS_ONE(3);
SELECT PLUS_ONE(1);
SELECT calls, rows, query FROM pg_stat_statements ORDER BY query COLLATE "C";
DROP FUNCTION PLUS_ONE(INTEGER);
-- immutable SQL function --- can be executed at plan time
CREATE FUNCTION PLUS_THREE(i INTEGER) RETURNS INTEGER AS
$$ SELECT i + 3 LIMIT 1 $$ IMMUTABLE LANGUAGE SQL;
SELECT PLUS_THREE(8);
SELECT PLUS_THREE(10);
SELECT toplevel, calls, rows, query FROM pg_stat_statements ORDER BY query COLLATE "C";
--
-- pg_stat_statements.track = none