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
Commit ddb17e387a attempted to avoid
confusing users by displaying digits after the decimal point only when
nloops > 1, since it's impossible to have a fraction row count after a
single iteration. However, this made the regression tests unstable since
parallal queries will have nloops>1 for all nodes below the Gather or
Gather Merge in normal cases, but if the workers don't start in time and
the leader finishes all the work, they will suddenly have nloops==1,
making it unpredictable whether the digits after the decimal point would
be displayed or not. Although 44cbba9a7f
seemed to fix the immediate failures, it may still be the case that there
are lower-probability failures elsewhere in the regression tests.
Various fixes are possible here. For example, it has previously been
proposed that we should try to display the digits after the decimal
point only if rows/nloops is an integer, but currently rows is storead
as a float so it's not theoretically an exact quantity -- precision
could be lost in extreme cases. It has also been proposed that we
should try to display the digits after the decimal point only if we're
under some sort of construct that could potentially cause looping
regardless of whether it actually does. While such ideas are not
without merit, this patch adopts the much simpler solution of always
display two decimal digits. If that approach stands up to scrutiny
from the buildfarm and human users, it spares us the trouble of doing
anything more complex; if not, we can reassess.
This commit incidentally reverts 44cbba9a7f,
which should no longer be needed.
Author: Robert Haas <robertmhaas@gmail.com>
Author: Ilia Evdokimov <ilya.evdokimov@tantorlabs.com>
Discussion: http://postgr.es/m/CA+TgmoazzVHn8sFOMFAEwoqBTDxKT45D7mvkyeHgqtoD2cn58Q@mail.gmail.com
Some utility statements contain queries that can be planned and
executed: CREATE TABLE AS and DECLARE CURSOR. This commit adds query ID
computation for the inner queries executed by these two utility
commands, with and without EXPLAIN. This change leads to four new
callers of JumbleQuery() and post_parse_analyze_hook() so as extensions
can decide what to do with this new data.
Previously, extensions relying on the query ID, like pg_stat_statements,
were not able to track these nested queries as the query_id was 0.
For pg_stat_statements, this commit leads to additions under !toplevel
when pg_stat_statements.track is set to "all", as shown in its
regression tests. The output of EXPLAIN for these two utilities gains a
"Query Identifier" if compute_query_id is enabled.
Author: Anthonin Bonnefoy
Reviewed-by: Michael Paquier, Jian He
Discussion: https://postgr.es/m/CAO6_XqqM6S9bQ2qd=75W+yKATwoazxSNhv5sjW06fjGAtHbTUA@mail.gmail.com
Previously, a Query generated through the transform phase would have
unset stmt_location, tracking the starting point of a query string.
Extensions relying on the statement location to extract its relevant
parts in the source text string would fallback to use the whole
statement instead, leading to confusing results like in
pg_stat_statements for queries relying on nested queries, like:
- EXPLAIN, with top-level and nested query using the same query string,
and a query ID coming from the nested query when the non-top-level
entry.
- Multi-statements, with only partial portions of queries being
normalized.
- COPY TO with a query, SELECT or DMLs.
This patch improves things by keeping track of the statement locations
and propagate it to Query during transform, allowing PGSS to only show
the relevant part of the query for nested query. This leads to less
bloat in entries for non-top-level entries, as queries can now be
grouped within the same (toplevel, queryid) duos in pg_stat_statements.
The result gives a stricter one-one mapping between query IDs and its
query strings.
The regression tests introduced in 45e0ba30fc produce differences
reflecting the new logic.
Author: Anthonin Bonnefoy
Reviewed-by: Michael Paquier, Jian He
Discussion: https://postgr.es/m/CAO6_XqqM6S9bQ2qd=75W+yKATwoazxSNhv5sjW06fjGAtHbTUA@mail.gmail.com
There have never been any regression tests in PGSS for various query
patterns for nested queries combined with level tracking, like:
- Multi-statements.
- CREATE TABLE AS
- CREATE/REFRESH MATERIALIZED VIEW
- DECLARE CURSOR
- EXPLAIN, with a subset of the above supported.
- COPY.
All the tests added here track historical, sometimes confusing, existing
behaviors. For example, EXPLAIN stores two PGSS entries with the same
top-level query string but two different query IDs as one is calculated
for the top-level EXPLAIN (this part is right) and a second one for the
inner query in the EXPLAIN (this part is not right).
A couple of patches are under discussion to improve the situation, and
all the tests added here will prove useful to evaluate the changes
discussed.
Author: Anthonin Bonnefoy
Reviewed-by: Michael Paquier, Jian He
Discussion: https://postgr.es/m/CAO6_XqqM6S9bQ2qd=75W+yKATwoazxSNhv5sjW06fjGAtHbTUA@mail.gmail.com
This is a continuation of work like 11c34b342b, done to reduce the
bloat of pg_stat_statements by applying more normalization to query
entries. This commit is able to detect and normalize values in
VariableSetStmt, resulting in:
SET conf_param = $1
Compared to other parse nodes, VariableSetStmt is embedded in much more
places in the parser, impacting many query patterns in
pg_stat_statements. A custom jumble function is used, with an extra
field in the node to decide if arguments should be included in the
jumbling or not, a location field being not enough for this purpose.
This approach allows for a finer tuning.
Clauses relying on one or more keywords are not normalized, for example:
* DEFAULT
* FROM CURRENT
* List of keywords. SET SESSION CHARACTERISTICS AS TRANSACTION,
where it is critical to differentiate different sets of options, is a
good example of why normalization should not happen.
Some queries use VariableSetStmt for some subclauses with SET, that also
have their values normalized:
- ALTER DATABASE
- ALTER ROLE
- ALTER SYSTEM
- CREATE/ALTER FUNCTION
ba90eac7a9 has added test coverage for most of the existing SET
patterns. The expected output of these tests shows the difference this
commit creates. Normalization could be perhaps applied to more portions
of the grammar but what is done here is conservative, and good enough as
a starting point.
Author: Greg Sabino Mullane, Michael Paquier
Discussion: https://postgr.es/m/36e5bffe-e989-194f-85c8-06e7bc88e6f7@amazon.com
Discussion: https://postgr.es/m/B44FA29D-EBD0-4DD9-ABC2-16F1CB087074@amazon.com
Discussion: https://postgr.es/m/CAKAnmmJtJY2jzQN91=2QAD2eAJAA-Per61eyO48-TyxEg-q0Rg@mail.gmail.com
For utility statements defined within a function, the query tree is
copied to a PlannedStmt as utility commands do not require planning.
However, the query ID was missing from the information passed down.
This leads to plugins relying on the query ID like pg_stat_statements to
not be able to track utility statements within function calls. Tests
are added to check this behavior, depending on pg_stat_statements.track.
This is an old bug. Now, query IDs for utilities are compiled using
their parsed trees rather than the query string since v16
(3db72ebcbe), leading to less bloat with utilities, so backpatch down
only to this version.
Author: Anthonin Bonnefoy
Discussion: https://postgr.es/m/CAO6_XqrGp-uwBqi3vBPLuRULKkddjC7R5QZCgsFren=8E+m2Sg@mail.gmail.com
Backpatch-through: 16
This is preliminary patch. It adds NOT NULL checking for the result of
pg_stat_statements_reset() function. It is needed for upcoming patch
"Track statement entry timestamp" that will change the result type of
this function to the timestamp of a reset performed.
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
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
As shaped, two DROP ROLE queries included in "user_activity" were
showing in the reports for "wal". The intention is to keep each test
isolated and independent, so this is incorrect. This commit adds some
calls to pg_stat_statements_reset() to clean up the statistics once each
test finishes, so as there are no risks of overlap in the reports for
individial scenarios.
The addition in "user_activity" fixes the output of "wal". The new
resets done in "level_tracking" and "utility" are added for consistency
with the rest, though they do not affect the stats generated in the
other tests.
Oversight in d0028e3.
Reported-by: Andrei Zubkov
Discussion: https://postgr.es/m/7beb722dd016bf54f1c78bfd6d44a684e28da624.camel@moonset.ru
pg_stat_statements.sql acts as the main file for all the core tests of
the module, but things have become complicated to follow over the years
as some of the sub-scenarios tested in this file rely on assumptions
that come from completely different areas of it, like a GUC setup or a
relation created previously. For example, row tracking for CTAS/COPY
was looking at the number of plans, which was not necessary, or level
tracking was mixed with checks on planner counts.
This commit refactors the tests of pg_stat_statements, by moving test
cases out of pg_stat_statements.sql into their own file, as of:
- Planning-related tests in planning.sql, for [re]plan counts and
top-level handling. These depend on pg_stat_statements.track_planning.
- Utilities in utility.sql (pg_stat_statements.track_utility), that
includes now the tests for:
-- Row tracking for CTAS, CREATE MATERIALIZED VIEW, COPY.
-- Basic utility statements.
-- SET statements.
- Tracking level, depending on pg_stat_statements.track. This part has
been looking at scenarios with DO blocks, PL functions and SQL
functions.
pg_stat_statements.sql (still named the same for now) still includes
some checks for role-level tracking and WAL generation metrics, that
ought to become independent in the long term for clarity.
While on it, this switches the order of the attributes when querying
pg_stat_statements, the query field becoming last. This makes much
easier the tracking of changes related to normalization, as queries are
the only variable-length attributes queried (unaligned mode would be one
extra choice, but that reduces the checks on the other fields).
Test scenarios and their results match exactly with what was happening
before this commit in terms of calls, number of plans, number of rows,
cached data or level tracking, so this has no effect on the coverage in
terms of what is produced by the reports in the table
pg_stat_statements. A follow-up patch will extend more the tests of
pg_stat_statements around utilities, so this split creates a foundation
for this purpose, without complicating more pg_stat_statements.sql.
Reviewed-by: Bertrand Drouvot
Discussion: https://postgr.es/m/Y+MRdEq9W9XVa2AB@paquier.xyz
