This batch is similar to 462fe0ff62 and addresses a variety of code
style issues, including grammar mistakes, typos, inconsistent variable
names in function declarations, and incorrect function names in comments
and documentation. These fixes have accumulated on the community
mailing lists since the commit mentioned above.
Notably, Alexander Lakhin previously submitted a patch identifying many
of the trivial typos and grammar issues that had been reported on
pgsql-hackers. His patch covered a somewhat large portion of the issues
addressed here, though not all of them.
The documentation changes only affect HEAD.
This one occurs when an outer join appears beneath the made-unique
side of a semijoin. The issue is that join RTEs are not featured
out of sj_unique_rels entries. Fix, and add a test case.
Reported-by: Alexander Lakhin <exclusion@gmail.com>
Analyzed-by: Tender Wang <tndrwang@gmail.com>
Discussion: http://postgr.es/m/c0c63979-43c2-4424-8fe8-56949934c9d8@gmail.com
It turns out that our main regression test suite queries tables upon
which concurrent DDL is occurring, which can, rarely, cause
test_plan_advice failures. We're not quite ready to fix that problem
just yet, because we want to gather some more information about how
often it actually happens first. But, our plan is going to require
test_plan_advice to access a few bits of pg_plan_advice that have
been considered internal up until now, so this commit rejiggers
things to expose those bits.
First, test_plan_advice is going to need to be able to interpret
the PGPA_TE_* constants which have been declared in pgpa_trove.h.
The "TE" stands for "trove entry" but that's kind of a silly name;
change the naming to "FB" (for "feedback") and move the declarations
to pg_plan_advice.h, which is a header file that's already installed.
This has the side benefit of making these constants available to any
other extensions that may want to examine plan advice feedback.
Second, test_plan_advice is going to call pgpa_planner_feedback_warning,
so make that function non-static and mark it PGDLLEXPORT.
Discussion: http://postgr.es/m/CA+TgmobOOmmXSJz3e+cjTY-bA1+W0dqVDqzxUBEvGtW62whYGg@mail.gmail.com
If a subquery is proven empty, and if that subquery contained a
semijoin, and if making one side or the other of that semijoin
unique and performing an inner join was a possible strategy, then
the previous code would fail with ERROR: no rtoffset for plan %s
when attempting to generate advice. Fix that.
Reported-by: Alexander Lakhin <exclusion@gmail.com>
Discussion: http://postgr.es/m/CA+TgmobOOmmXSJz3e+cjTY-bA1+W0dqVDqzxUBEvGtW62whYGg@mail.gmail.com
When a tablesample routine says that it is not repeatable across
scans, set_tablesample_rel_pathlist will (usually) materialize it,
confusing pg_plan_advice's plan walker machinery. To fix, update that
machinery to view such Material paths as essentially an extension of
the underlying scan.
Reported-by: Alexander Lakhin <exclusion@gmail.com>
Discussion: http://postgr.es/m/CA+TgmobOOmmXSJz3e+cjTY-bA1+W0dqVDqzxUBEvGtW62whYGg@mail.gmail.com
It would be useful to be able to tell auto_explain to set a custom
EXPLAIN option, but it would be bad if it tried to do so and the
option name or value wasn't valid, because then every query would fail
with a complaint about the EXPLAIN option. So add a guc_check_handler
that auto_explain will be able to use to only try to set option
name/value/type combinations that have been determined to be legal,
and to emit useful messages about ones that aren't.
Reviewed-by: Matheus Alcantara <matheusssilv97@gmail.com>
Reviewed-by: Lukas Fittl <lukas@fittl.com>
Discussion: http://postgr.es/m/CA+Tgmob-0W8306mvrJX5Urtqt1AAasu8pi4yLrZ1XfwZU-Uj1w@mail.gmail.com
An Append node that is part of a partitionwise aggregate has no
apprelids. If such a node was elided, the previous coding would
attempt to call unique_nonjoin_rtekind() on a NULL pointer, which
leads to an assertion failure. Insert a NULL check to prevent that.
Reported-by: Alexander Lakhin <exclusion@gmail.com>
Discussion: http://postgr.es/m/0afba1ce-c946-4131-972d-191d9a1c097c@gmail.com
The premise of src/test/modules/test_plan_advice is that if we plan
a query once, generate plan advice, and then replan it using that
same advice, all of that advice should apply cleanly, since the
settings and everything else are the same. Unfortunately, that's
not the case: the test suite is the main regression tests, and
concurrent activity can change the statistics on tables involved
in the query, especially system catalogs. That's OK as long as it
only affects costing, but in a few cases, it affects which relations
appear in the final plan at all.
In the buildfarm failures observed to date, this happens because
we consider alternative subplans for the same portion of the query;
in theory, MinMaxAggPath is vulnerable to a similar hazard. In both
cases, the planner clones an entire subquery, and the clone has a
different plan name, and therefore different range table identifiers,
than the original. If a cost change results in flipping between one
of these plans and the other, the test_plan_advice tests will fail,
because the range table identifiers to which advice was applied won't
even be present in the output of the second planning cycle.
To fix, invent a new DO_NOT_SCAN advice tag. When generating advice,
emit it for relations that should not appear in the final plan at
all, because some alternative version of that relation was used
instead. When DO_NOT_SCAN is supplied, disable all scan methods for
that relation.
To make this work, we reuse a bunch of the machinery that previously
existed for the purpose of ensuring that we build the same set of
relation identifiers during planning as we do from the final
PlannedStmt. In the process, this commit slightly weakens the
cross-check mechanism: before this commit, it would fire whenever
the pg_plan_advice module was loaded, even if pg_plan_advice wasn't
actually doing anything; now, it will only engage when we have some
other reason to create a pgpa_planner_state. The old way was complex
and didn't add much useful test coverage, so this seems like an
acceptable sacrifice.
Discussion: http://postgr.es/m/CA+TgmoYuWmN-00Ec5pY7zAcpSFQUQLbgAdVWGR9kOR-HM-fHrA@mail.gmail.com
Reviewed-by: Lukas Fittl <lukas@fittl.com>
pg_plan_advice tracks two pieces of per-PlannerInfo data: (1) for each
RTI, the corresponding relation identifier, for purposes of
cross-checking those calculations against the final plan; and (2) the
set of semijoins seen during planning for which the strategy of making
one side unique was considered. The former is tracked using a hash
table that uses <plan_name, RTI> as the key, and the latter is
tracked using a List of <plan_name, relids>.
It seems better to track both of these things in the same way and
to try to reuse some code instead of having everything be completely
separate, so invent pgpa_planner_info; we'll create one every time we
see a new PlannerInfo and need to associate some data with it, and
we'll use the plan_name field to distinguish between PlannerInfo
objects, as it should always be unique. Then, refactor the two
systems mentioned above to use this new infrastructure.
(Note that the adjustment in pgpa_plan_walker is necessary in order
to avoid spuriously triggering the sanity check in that function,
in the case where a pgpa_planner_info is created for a purpose not
related to sj_unique_rels.)
Discussion: https://postgr.es/m/CA+TgmoaK=4w7-qknUo3QhUJ53pXZq=c=KgZmRyD+k7ytqfmgSg@mail.gmail.com
Reviewed-by: Lukas Fittl <lukas@fittl.com>
The second half of this file is meant to test feedback, not
generated advice, and is meant to use the statements that it
prepares, not leftover prepared statements from earlier in the
file.
These mistakes resulted in failures under debug_discard_caches = 1,
because re-executing pt2 instead of executing pt4 for the first
time resulted in different output depending on whether the query
was replanned.
Reported-by: Tom Lane <tgl@sss.pgh.pa.us> (per BF member avocet)
The previous code could allocate pgpa_sj_unique_rel objects in a context
that had too short a lifespan. Fix by allocating them (and any
associated List-related allocations) in the same context as the
pgpa_planner_state to which they are attached. We also need to copy
uniquerel->relids, because the associated RelOptInfo may also be
allocated within a short-lived context.
Reported-by: Alexander Lakhin <exclusion@gmail.com>
Discussion: http://postgr.es/m/a6e6d603-e847-44dc-acd5-879fb4570062@gmail.com
The Makefile failed to set HEADERS_pg_plan_advice, so the header wasn't
installed. Fixing that reveals another problem: since this is just a
loadable module, not an extension, the header file is installed into
$(includedir_server)/contrib rather than $(includedir_server)/extension.
While we have no existing cases of installing header files there, it
appears to be the intent of pgxs.mk. However, this is inconsistent with
meson.build, which was using dir_include_extension. Changing that to
dir_include_server / 'contrib' makes the install locations consistent
across the two builds.
Author: Zsolt Parragi <zsolt.parragi@percona.com>
Discussion: http://postgr.es/m/CAN4CZFP6NOjv__4Mx+iQD8StdpbHvzDAatEQn2n15UKJ=MySSQ@mail.gmail.com
TOK_IDENT allows only non-keywords; identifier should be used
any place where either keywords or non-keywords should be accepted.
Hence, without this commit, any string that happens to be a keyword
can't be used as a partition schema, partition name, or plan name,
which is incorrect.
Author: Lukas Fittl <lukas@fittl.com>
Discussion: http://postgr.es/m/CAP53PkzKeD=t90OfeMsniYrcRe2THQbUx3g6wV17Y=ZtiwmWTQ@mail.gmail.com
Since commit 5883ff30b0, some compilers have been warning that the
rtekind variable in unique_nonjoin_rtekind() may be used
uninitialized. There doesn't appear to be any actual risk, so
let's just initialize it to something to silence the compiler
warnings.
Author: Sami Imseih <samimseih@gmail.com>
Discussion: https://postgr.es/m/CAA5RZ0sieVNfniCKMDdDjuXGd1OuzMQfTS5%3D9vX3sa-iiujKUA%40mail.gmail.com
Provide a facility that (1) can be used to stabilize certain plan choices
so that the planner cannot reverse course without authorization and
(2) can be used by knowledgeable users to insist on plan choices contrary
to what the planner believes best. In both cases, terrible outcomes are
possible: users should think twice and perhaps three times before
constraining the planner's ability to do as it thinks best; nevertheless,
there are problems that are much more easily solved with these facilities
than without them.
This patch takes the approach of analyzing a finished plan to produce
textual output, which we call "plan advice", that describes key
decisions made during plan; if that plan advice is provided during
future planning cycles, it will force those key decisions to be made in
the same way. Not all planner decisions can be controlled using advice;
for example, decisions about how to perform aggregation are currently
out of scope, as is choice of sort order. Plan advice can also be edited
by the user, or even written from scratch in simple cases, making it
possible to generate outcomes that the planner would not have produced.
Partial advice can be provided to control some planner outcomes but not
others.
Currently, plan advice is focused only on specific outcomes, such as
the choice to use a sequential scan for a particular relation, and not
on estimates that might contribute to those outcomes, such as a
possibly-incorrect selectivity estimate. While it would be useful to
users to be able to provide plan advice that affects selectivity
estimates or other aspects of costing, that is out of scope for this
commit.
Reviewed-by: Lukas Fittl <lukas@fittl.com>
Reviewed-by: Jakub Wartak <jakub.wartak@enterprisedb.com>
Reviewed-by: Greg Burd <greg@burd.me>
Reviewed-by: Jacob Champion <jacob.champion@enterprisedb.com>
Reviewed-by: Haibo Yan <tristan.yim@gmail.com>
Reviewed-by: Dian Fay <di@nmfay.com>
Reviewed-by: Ajay Pal <ajay.pal.k@gmail.com>
Reviewed-by: John Naylor <johncnaylorls@gmail.com>
Reviewed-by: Alexandra Wang <alexandra.wang.oss@gmail.com>
Discussion: http://postgr.es/m/CA+TgmoZ-Jh1T6QyWoCODMVQdhTUPYkaZjWztzP1En4=ZHoKPzw@mail.gmail.com
