This commit reverts the two following commits:
- 499edb0974, track more precisely query locations for nested
statements.
- 06450c7b8c, a follow-up fix of 499edb0974 with query locations.
The test introduced in this commit is not reverted. This is proving
useful to track a problem that only pgaudit was able to detect.
These prove to have issues with the tracking of SELECT statements, when
these use multiple parenthesis which is something supported by the
grammar. Incorrect location and lengths are causing pg_stat_statements
to become confused, failing its job in query normalization with
potential out-of-bound writes because the location and the length may
not match with what can be handled. A lot of the query patterns
discussed when this issue was reported have no test coverage in the main
regression test suite, or the recovery test 027_stream_regress.pl would
have caught the problems as pg_stat_statements is loaded by the node
running the regression tests. A first step would be to improve the test
coverage to stress more the query normalization logic.
A different portion of this work was done in 45e0ba30fc, with the
addition of tests for nested queries. These can be left in the tree.
They are useful to track the way inner queries are currently tracked by
PGSS with non-top-level entries, and will be useful when reconsidering
in the future the work reverted here.
Reported-by: Alexander Kozhemyakin <a.kozhemyakin@postgrespro.ru>
Discussion: https://postgr.es/m/18947-cdd2668beffe02bf@postgresql.org
The statement location calculated for some nested query cases was wrong
when multiple queries are sent as a single string, these being separated
by semicolons. As pointed by Sami Imseih, the location calculation was
incorrect when the last query of nested statement with multiple queries
does **NOT** finish with a semicolon for the last statement. In this
case, the statement length tracked by RawStmt is 0, which is equivalent
to say that the string should be used until its end. The code
previously discarded this case entirely, causing the location to remain
at 0, the same as pointing at the beginning of the string. This caused
pg_stat_statements to store incorrect query strings.
This issue has been introduced in 499edb0974. I have looked at the
diffs generated by pgaudit back then, and noticed the difference
generated for this nested query case, but I have missed the point that
it was an actual regression with an existing case. A test case is added
in pg_stat_statements to provide some coverage, restoring the pre-17
behavior for the calculation of the query locations. Special thanks to
David Steele, who, through an analysis of the test diffs generated by
pgaudit with the new v18 logic, has poked me about the fact that my
original analysis of the matter was wrong.
The test output of pg_overexplain is updated to reflect the new logic,
as the new locations refer to the beginning of the argument passed to
the function explain_filter(). When the module was introduced in
8d5ceb113e, which was after 499edb0974 (for the new calculation
method), the locations of the test were not actually right: the plan
generated for the query string given in input of the function pointed to
the top-level query, not the nested one.
Reported-by: David Steele <david@pgbackrest.org>
Author: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Anthonin Bonnefoy <anthonin.bonnefoy@datadoghq.com>
Reviewed-by: Jian He <jian.universality@gmail.com>
Reviewed-by: Sami Imseih <samimseih@gmail.com>
Reviewed-by: David Steele <david@pgbackrest.org>
Discussion: https://postgr.es/m/844a3b38-bbf1-4fb2-9fd6-f58c35c09917@pgbackrest.org
It added bogus whitespace at the end of a line in the documentation.
It should not have done that.
The pg_overexplain tests must SET debug_parallel_query = false,
not just RESET debug_parallel_query, or we get failures on test
machines that make debug_parallel_query = true the defualt.
There's a fair amount of information in the Plan and PlanState trees
that isn't printed by any existing EXPLAIN option. This means that,
when working on the planner, it's often necessary to rely on facilities
such as debug_print_plan, which produce excessively voluminous
output. Hence, use the new EXPLAIN extension facilities to implement
EXPLAIN (DEBUG) and EXPLAIN (RANGE_TABLE) as extensions to the core
EXPLAIN facility.
A great deal more could be done here, and the specific choices about
what to print and how are definitely arguable, but this is at least
a starting point for discussion and a jumping-off point for possible
future improvements.
Reviewed-by: Sami Imseih <samimseih@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviweed-by: Andrei Lepikhov <lepihov@gmail.com> (who didn't like it)
Discussion: http://postgr.es/m/CA+TgmoZfvQUBWQ2P8iO30jywhfEAKyNzMZSR+uc2xr9PZBw6eQ@mail.gmail.com
