Commit Graph

53534 Commits

Author SHA1 Message Date
Michael Paquier 3603f7c6e6 Remove WalCompressionMethod in favor of pg_compress_algorithm
The same structure, with the same set of elements (for none, lz4, gzip
and zstd), exists in compression.h, so let's make use of the centralized
version instead of duplicating things.  Some of the variables used
previously for WalCompressionMethod are renamed to stick better with the
new structure and routine names.

WalCompressionMethod was leading to some confusion in walmethods.c, as
it was sometimes used to refer to some data unrelated to WAL.

Reported-by: Robert Haas
Author: Michael Paquier
Reviewed-by: Robert Haas, Georgios Kokolatos
Discussion: https://postgr.es/m/YlPQGNAAa04raObK@paquier.xyz
2022-04-12 17:28:17 +09:00
Alvaro Herrera ce4f46fdc8
Change mechanism to set up source targetlist in MERGE
We were setting MERGE source subplan's targetlist by expanding the
individual attributes of the source relation completely, early in the
parse analysis phase.  This failed to work when the condition of an
action included a whole-row reference, causing setrefs.c to error out
with
  ERROR:  variable not found in subplan target lists
because at that point there is nothing to resolve the whole-row
reference with.  We can fix this by having preprocess_targetlist expand
the source targetlist for Vars required from the source rel by all
actions.  Moreover, by using this expansion mechanism we can do away
with the targetlist expansion in transformMergeStmt, which is good
because then we no longer pull in columns that aren't needed for
anything.

Add a test case for the problem.

While at it, remove some redundant code in preprocess_targetlist():
MERGE was doing separately what is already being done for UPDATE/DELETE,
so we can just rely on the latter and remove the former.  (The handling
of inherited rels was different for MERGE, but that was a no-longer-
necessary hack.)

Fix outdated, related comments for fix_join_expr also.

Author: Richard Guo <guofenglinux@gmail.com>
Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Reported-by: Joe Wildish <joe@lateraljoin.com>
Discussion: https://postgr.es/m/fab3b90a-914d-46a9-beb0-df011ee39ee5@www.fastmail.com
2022-04-12 09:29:39 +02:00
Michael Paquier a4b57543ac Rename backup_compression.{c,h} to compression.{c,h}
Compression option handling (level, algorithm or even workers) can be
used across several parts of the system and not only base backups.
Structures, objects and routines are renamed in consequence, to remove
the concept of base backups from this part of the code making this
change straight-forward.

pg_receivewal, that has gained support for LZ4 since babbbb5, will make
use of this infrastructure for its set of compression options, bringing
more consistency with pg_basebackup.  This cleanup needs to be done
before releasing a beta of 15.  pg_dump is a potential future target, as
well, and adding more compression options to it may happen in 16~.

Author: Michael Paquier
Reviewed-by: Robert Haas, Georgios Kokolatos
Discussion: https://postgr.es/m/YlPQGNAAa04raObK@paquier.xyz
2022-04-12 13:38:54 +09:00
Tom Lane bd037dc928 Make XLogRecGetBlockTag() throw error if there's no such block.
All but a few existing callers assume without checking that this
function succeeds.  While it probably will, that's a poor excuse for
not checking.  Let's make it return void and instead throw an error
if it doesn't find the block reference.  Callers that actually need
to handle the no-such-block case must now use the underlying function
XLogRecGetBlockTagExtended.

In addition to being a bit less error-prone, this should also serve
to suppress some Coverity complaints about XLogRecGetBlockRefInfo.

While at it, clean up some inconsistency about use of the
XLogRecHasBlockRef macro: make XLogRecGetBlockTagExtended use
that instead of open-coding the same condition, and avoid calling
XLogRecHasBlockRef twice in relevant code paths.  (That is,
calling XLogRecHasBlockRef followed by XLogRecGetBlockTag is now
deprecated: use XLogRecGetBlockTagExtended instead.)

Patch HEAD only; this doesn't seem to have enough value to consider
a back-branch API break.

Discussion: https://postgr.es/m/425039.1649701221@sss.pgh.pa.us
2022-04-11 17:43:53 -04:00
Peter Geoghegan 9debd12348 Remove comment about historic heap vacuuming issue.
Remove comment block about how heap page vacuuming used to set tuples
with storage to LP_UNUSED in a rare edge case that can no longer happen
following commit 8523492d4e.  The comments seem unnecessary now, since
it's now generally clear that heap vacuuming only applies to LP_DEAD
items from VACUUM's first heap pass following more recent work from
commits 12b5ade902 and 4f8d9d1217.
2022-04-11 14:20:46 -07:00
Tom Lane 9de692c101 Remove dead code in do_pg_backup_start().
As of commit 39969e2a1, no caller of do_pg_backup_start() passes NULL
for labelfile or tblspcmapfile, nor is it plausible that any would
do so in the future.  Remove the code that coped with that case,
as (a) it's dead and (b) it causes Coverity to bleat about possibly
leaked storage.

While here, do some janitorial work on the function's header comment.
2022-04-11 15:56:01 -04:00
Tom Lane 5e70d8b5d1 Tweak the default behavior of psql's \dconfig.
\dconfig without an argument originally printed all parameters,
but it seems more useful to print only those parameters with
non-default settings.  You can easily get the show-everything
behavior with "\dconfig *", but that output is unwieldy and
seems unlikely to be wanted very often.

Per suggestion from Christoph Berg.

Discussion: https://postgr.es/m/YlFQLzlPi4QD0wSi@msg.df7cb.de
2022-04-11 15:11:46 -04:00
Tom Lane 3c702b3ed1 Explicitly ignore guaranteed-true result from pgstat_lock_entry().
With nowait passed as false, pgstat_lock_entry() must return true
so there's no need to check its result.  Coverity seems unconvinced
of this, so whack it upside the head with a (void) cast.
2022-04-11 13:22:37 -04:00
Tom Lane 93fcf2d209 fgetc() returns int, not char.
This has no practical effect, since this code doesn't actually need to
distinguish EOF (-1) from \0377; but it silences a Coverity complaint.
2022-04-11 13:15:46 -04:00
Jeff Davis 8638c76cc9 Doc build fix: remove tab from filelist.sgml.
Author: Amit Kapila
Discussion: https://postgr.es/m/CAA4eK1K6z=gu-jppU1dtsyr2BC-pzrq3TYe=RfY+w386dfdiFA@mail.gmail.com
2022-04-11 08:52:27 -07:00
Andrew Dunstan b46bcf7a4b Improve readability of SQL/JSON documentation.
Per review from Justin Pryzby.

Discussion: https://postgr.es/m/f50aca87-6b35-a1b0-2286-f815a589dd83@dunslane.net
2022-04-11 11:51:26 -04:00
Peter Eisentraut c215cc7b61 Add color support for new frontend detail/hint messages
As before, the defaults are similar to gcc's default appearance.
2022-04-11 17:36:44 +02:00
Tom Lane dfd0f2bbc5 Avoid re-writing files unnecessarily in src/tools/copyright.pl.
The existing coding resulted in touching every copyright-containing
file in the tree, even if it was already up to date.  That doesn't
matter much for the annual run, but it's an annoyance if you try
to use the script for mop-up at the close of a devel cycle, as
I just did.

Discussion: https://postgr.es/m/266030.1649685473@sss.pgh.pa.us
2022-04-11 11:20:20 -04:00
Robert Haas ad385a494f docs: Note the recovery_min_apply_delay bloats pg_wal.
Those WAL files that we're waiting to apply have to be stored
somewhere.

Thom Brown

Discussion: http://postgr.es/m/CAA-aLv4SkJRK6GGcd0Axt8kt6_eWMEbtG7f8NJpFh+rNshtdNA@mail.gmail.com
2022-04-11 10:52:18 -04:00
David Rowley e0064f0ff6 Docs: Mention that relpersistence is for sequences now too
Per 344d62fb9.

Author: Justin Pryzby
Discussion: https://postgr.es/m/20220411020336.GB26620@telsasoft.com
2022-04-11 20:50:20 +12:00
David Rowley b0e5f02ddc Fix various typos and spelling mistakes in code comments
Author: Justin Pryzby
Discussion: https://postgr.es/m/20220411020336.GB26620@telsasoft.com
2022-04-11 20:49:41 +12:00
David Rowley bba3c35b29 Docs: Fix various mistakes and typos
Author: Justin Pryzby
Discussion: https://postgr.es/m/20220411020336.GB26620@telsasoft.com
2022-04-11 20:48:48 +12:00
Michael Paquier 7597cc3083 Fix the dates of some copyright notices
0ad8032 and 4e34747 are at the origin of that.  Julien has found the one
in parse_jsontable.c, while I have spotted the rest.

Author: Julien Rouhaud, Michael Paquier
Discussion: https://postgr.es/m/20220411060838.ftnzyvflpwu6f74w@jrouhaud
2022-04-11 16:36:25 +09:00
Peter Eisentraut 0c65177a21 Put new command-line options into alphabetical order in help output 2022-04-11 07:39:25 +02:00
Michael Paquier 8ac700acff doc: Clarify behavior of query planner locking with REINDEX
The documentation of REINDEX has never mentioned that the query planner
may take an ACCESS SHARE lock on the indexes depending on the query
used.  This adds also a note about prepared queries not impacted when
they do not use the index(es) rebuilt.

Author: Frédéric Yhuel
Reviewed-by: Guillaume Lelarge, Justin Pryzby
Discussion: https://postgr.es/m/65d08718-6f11-978a-4b5a-72b807d4c663@dalibo.com
2022-04-11 09:49:13 +09:00
Daniel Gustafsson cd959b1b06 Doc: fix typos in documentation
Commits 39969e2a1e and 5c279a6d35 accidentally included a typo each
in the user facing documentation.
2022-04-10 21:42:43 +02:00
Tom Lane b6b8824ee7 Doc: reformat descriptions of pgbench output formats.
This is mostly driven by trying to get rid of line-too-wide
warnings in PDF output; but I think converting to a <variablelist>
makes it more readable anyway.

Discussion: https://postgr.es/m/4183048.1649536705@sss.pgh.pa.us
2022-04-10 15:31:42 -04:00
Andrew Dunstan c835dcdab6
Fix pgperlsyncheck following SSL TAP test refactoring
Commit 4a7e964fc6 made pgperlsyncheck fail, but apparently nobody
noticed, although the buildfarm module that does more or less the same
thing was modified. So fix the in-core test. I will look at unifying the
two sets of tests so we avoid a future mismatch.
2022-04-10 09:19:21 -04:00
Andrew Dunstan 3b0a42e74e
Add timestamp and elapsed time decorations to TAP test logs
These apply to traces from Test::More functions such as ok(), is(),
diag() and note(). Output from other sources (e.g. external programs
such a initdb) is not affected. The elapsed time is the time since the
last such trace (or the beginning of the test in the first case). Times
and timestamps are at millisecond precision.

Discussion: https://postgr.es/m/20220401172150.rsycz4lrn7ewruil@alap3.anarazel.de
2022-04-10 09:19:09 -04:00
Tom Lane 7b735f8b52 Doc: shorten JSON_SERIALIZE example to avoid a PDF build warning.
There's no particular reason why this example has to use a
3-element array rather than 2-element.  Shortening it makes
the result bytea narrow enough to not cause a margin overrun
in A4 format.
2022-04-09 15:09:38 -04:00
Peter Eisentraut 80c877271a Fix whitespace 2022-04-09 16:17:41 +02:00
Peter Eisentraut 38abc39c81 Add missing serial commas 2022-04-09 16:15:01 +02:00
Peter Eisentraut fc5b83bb60 Add missing source files to nls.mk 2022-04-09 15:46:37 +02:00
Tom Lane c0d1c641cb Silence compiler warnings for unsupported compression methods.
wrasse, at least, moans about the lack of any "return" statement
in these functions.  You'd think pretty much everything would
know that exit(1) doesn't return, but evidently not.
2022-04-08 18:14:24 -04:00
Tom Lane 9a374b77fb Improve frontend error logging style.
Get rid of the separate "FATAL" log level, as it was applied
so inconsistently as to be meaningless.  This mostly involves
s/pg_log_fatal/pg_log_error/g.

Create a macro pg_fatal() to handle the common use-case of
pg_log_error() immediately followed by exit(1).  Various
modules had already invented either this or equivalent macros;
standardize on pg_fatal() and apply it where possible.

Invent the ability to add "detail" and "hint" messages to a
frontend message, much as we have long had in the backend.

Except where rewording was needed to convert existing coding
to detail/hint style, I have (mostly) resisted the temptation
to change existing message wording.

Patch by me.  Design and patch reviewed at various stages by
Robert Haas, Kyotaro Horiguchi, Peter Eisentraut and
Daniel Gustafsson.

Discussion: https://postgr.es/m/1363732.1636496441@sss.pgh.pa.us
2022-04-08 14:55:14 -04:00
Tom Lane 5c431c7fb3 Fix busted .gitignore entry.
Typo in commit 2258e76f9.
2022-04-08 14:22:47 -04:00
Robert Haas f37015a161 Rename delayChkpt to delayChkptFlags.
Before commit 412ad7a556, delayChkpt
was a Boolean. Now it's an integer. Extensions using it need to be
appropriately updated, so let's rename the field to make sure that
a hard compilation failure occurs.

Replacing delayChkpt with delayChkptFlags made a few comments extend
past 80 characters, so I reflowed them and changed some wording very
slightly.

The back-branches will need a different change to restore compatibility
with existing minor releases; this is just for master.

Per suggestion from Tom Lane.

Discussion: http://postgr.es/m/a7880f4d-1d74-582a-ada7-dad168d046d1@enterprisedb.com
2022-04-08 11:44:17 -04:00
Peter Eisentraut 891624f0ec psql: Fix translation marking
Commit 5a2832465f added
addFooterToPublicationDesc() as a wrapper around
printTableAddFooter().  The translation marker _() was moved to the
body of addFooterToPublicationDesc(), but addFooterToPublicationDesc()
was not added to GETTEXT_TRIGGERS, so those strings were lost for
translation.  To fix, add the translation markers to the call sites of
addFooterToPublicationDesc() and remove the translation marker from
the body of the function.  This seems easiest since there were only
two callers and it keeps the API consistent with
printTableAddFooter().  While we're here, add some const decorations
to the prototype of addFooterToPublicationDesc() for consistency with
printTableAddFooter().
2022-04-08 15:16:33 +02:00
Robert Haas 8ec569479f Apply PGDLLIMPORT markings broadly.
Up until now, we've had a policy of only marking certain variables
in the PostgreSQL header files with PGDLLIMPORT, but now we've
decided to mark them all. This means that extensions running on
Windows should no longer operate at a disadvantage as compared to
extensions running on Linux: if the variable is present in a header
file, it should be accessible.

Discussion: http://postgr.es/m/CA+TgmoYanc1_FSfimhgiWSqVyP5KKmh5NP2BWNwDhO8Pg2vGYQ@mail.gmail.com
2022-04-08 08:16:38 -04:00
Robert Haas 80900d4690 Helper script to apply PGDLLIMPORT markings.
This script isn't terribly smart and won't necessarily catch every
case, but it catches many of them and is better than a totally
manual approach.

Patch by me, reviewed by Andrew Dunstan.

Discussion: http://postgr.es/m/CA+TgmoYanc1_FSfimhgiWSqVyP5KKmh5NP2BWNwDhO8Pg2vGYQ@mail.gmail.com
2022-04-08 08:06:10 -04:00
Magnus Hagander 57d6aea00f Add JIT counters to pg_stat_statements
This adds cumulative counters for jit operations to pg_stat_statements,
making it easier to diagnose how JIT is used in an installation.

These changes merge into the 1.10 changes applied in 76cbf7edb6 without
creating a new version.

Reviewed-By: Julien Rouhaud
Discussion: https://www.postgresql.org/message-id/flat/CABUevEySt4NTYqvWzwyAW_0-jG1bjN-y+tykapAnA0FALOs+Lw@mail.gmail.com
2022-04-08 13:52:16 +02:00
Jeff Davis dad9ba1c82 Fix buildfarm failures in pg_walinspect tests. 2022-04-08 03:21:12 -07:00
Jeff Davis 12aaae5131 Check XLogRecHasBlockRef() before XLogRecHasBlockImage().
Trial fix of buildfarm failures on kestrel and tamandua.
2022-04-08 02:30:57 -07:00
Jeff Davis 1562e92c62 Fix buildfarm failure from commit 2258e76f90. 2022-04-08 01:33:58 -07:00
Jeff Davis 2258e76f90 Add contrib/pg_walinspect.
Provides similar functionality to pg_waldump, but from a SQL interface
rather than a separate utility.

Author: Bharath Rupireddy
Reviewed-by: Greg Stark, Kyotaro Horiguchi, Andres Freund, Ashutosh Sharma, Nitin Jadhav, RKN Sai Krishna
Discussion: https://postgr.es/m/CALj2ACUGUYXsEQdKhEdsBzhGEyF3xggvLdD8C0VT72TNEfOiog%40mail.gmail.com
2022-04-08 00:26:44 -07:00
Peter Eisentraut 708007dced Remove error message hints mentioning configure options
These are usually not useful since users will use packaged
distributions and won't be interested in rebuilding their installation
from source.  Also, we have only used these kinds of hints for some
features and in some places, not consistently throughout.

Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/2552aed7-d0e9-280a-54aa-2dc7073f371d%40enterprisedb.com
2022-04-08 07:41:55 +02:00
Andres Freund b3abca6810 pgstat: Update docs to match the shared memory stats reality.
This includes removing documentation for stats_temp_directory, adding
documentation for stats_fetch_consistency, rephrasing references to the stats
collector and documenting that starting a cleanly shut down standby will not
remove stats anymore. The latter point might require further wordsmithing, it
wasn't easy to adjust some of the existing content.

Author: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Author: Andres Freund <andres@anarazel.de>
Reviewed-By: Thomas Munro <thomas.munro@gmail.com>
Reviewed-By: Justin Pryzby <pryzby@telsasoft.com>
Reviewed-By: "David G. Johnston" <david.g.johnston@gmail.com>
Reviewed-By: Lukas Fittl <lukas@fittl.com>
Discussion: https://postgr.es/m/20220303021600.hs34ghqcw6zcokdh@alap3.anarazel.de
2022-04-07 21:35:35 -07:00
Michael Paquier 76cbf7edb6 pg_stat_statements: Track I/O timing for temporary file blocks
This commit adds two new columns to pg_stat_statements, called
temp_blk_read_time and temp_blk_write_time.  Those columns respectively
show the time spent to read and write temporary file blocks on disk,
whose tracking has been added in efb0ef9.  This information is
available when track_io_timing is enabled, like blk_read_time and
blk_write_time.

pg_stat_statements is updated to version to 1.10 as an effect of the
newly-added columns.  Tests for the upgrade path 1.9->1.10 are added.

PGSS_FILE_HEADER is bumped for the new stats file format.

Author: Masahiko Sawada
Reviewed-by: Georgios Kokolatos, Melanie Plageman, Julien Rouhaud,
Ranier Vilela
Discussion: https://postgr.es/m/CAD21AoAJgotTeP83p6HiAGDhs_9Fw9pZ2J=_tYTsiO5Ob-V5GQ@mail.gmail.com
2022-04-08 13:12:07 +09:00
Andrew Dunstan a6baa4badd Documentation for SQL/JSON features
This documents the features added in commits f79b803dcc, f4fb45d15c,
33a377608f, 1a36bc9dba, 606948b058, 49082c2cc3, 4e34747c88, and
fadb48b00e.

I have cleaned up the aggregate section of the submitted docs, but there
is still a deal of copy editing required. However, I thought it best to
have some documentation sooner rather than later so testers can have a
better idea what they are playing with.

Nikita Glukhov

Reviewers have included (in no particular order) Andres Freund, Alexander
Korotkov, Pavel Stehule, Andrew Alsup, Erik Rijkers, Zhihong Yu,
Himanshu Upadhyaya, Daniel Gustafsson, Justin Pryzby.

Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru
Discussion: https://postgr.es/m/7e2cb85d-24cf-4abb-30a5-1a33715959bd@postgrespro.ru
2022-04-07 23:46:03 -04:00
Michael Paquier efb0ef909f Track I/O timing for temporary file blocks in EXPLAIN (BUFFERS)
Previously, the output of EXPLAIN (BUFFERS) option showed only the I/O
timing spent reading and writing shared and local buffers.  This commit
adds on top of that the I/O timing for temporary buffers in the output
of EXPLAIN (for spilled external sorts, hashes, materialization. etc).
This can be helpful for users in cases where the I/O related to
temporary buffers is the bottleneck.

Like its cousin, this information is available only when track_io_timing
is enabled.  Playing the patch, this is showing an extra overhead of up
to 1% even when using gettimeofday() as implementation for interval
timings, which is slightly within the usual range noise still that's
measurable.

Author: Masahiko Sawada
Reviewed-by: Georgios Kokolatos, Melanie Plageman, Julien Rouhaud,
Ranier Vilela
Discussion: https://postgr.es/m/CAD21AoAJgotTeP83p6HiAGDhs_9Fw9pZ2J=_tYTsiO5Ob-V5GQ@mail.gmail.com
2022-04-08 11:27:21 +09:00
Thomas Munro dafae9707a Fix recovery_prefetch docs.
Correct a typo and a couple of sentences that weren't updated to reflect
recent changes to the code.

Reported-by: Justin Pryzby <pryzby@telsasoft.com>
Discussion: https://postgr.es/m/20220407125555.GC24419%40telsasoft.com
2022-04-08 13:43:37 +12:00
Andres Freund d6c0db1483 pgstat: Hide instability in stats.spec with -DCATCACHE_FORCE_RELEASE.
With -DCATCACHE_FORCE_RELEASE a few tests failed. Those were trying to test
behavior in the absence of invalidation processing and
-DCATCACHE_FORCE_RELEASE obviously adds a lot of invalidation processing. The
test already tried to handle debug_discard_caches > 0, by disabling it for
individual tests.

Instead hide potentially problematic function calls in a wrapper function that
catches the does-not-exist error. The error isn't the actually interesting
bit, it's whether the stats entry still exist afterwards.

I confirmed that the tests still catches leaked function stats if I nuke the
protections against that in pgstat_function.c.

Per buildfarm animal prion.

Discussion: https://postgr.es/m/20220407165709.jgdkrzqlkcwue6ko@alap3.anarazel.de
2022-04-07 18:20:50 -07:00
Andres Freund 5264add784 pgstat: add/extend tests for resetting various kinds of stats.
- subscriber stats reset path was untested
- slot stat sreset path for all slots was untested
- pg_stat_database.sessions etc was untested
- pg_stat_reset_shared() was untested, for any kind of shared stats
- pg_stat_reset() was untested

Author: Melanie Plageman <melanieplageman@gmail.com>
Author: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/20220303021600.hs34ghqcw6zcokdh@alap3.anarazel.de
2022-04-07 15:43:43 -07:00
Peter Geoghegan 10a8d13823 Truncate line pointer array during heap pruning.
Reclaim space from the line pointer array when heap pruning leaves
behind a contiguous group of LP_UNUSED items at the end of the array.
This happens during subsequent page defragmentation.  Certain kinds of
heap line pointer bloat are ameliorated by this new optimization.

Follow-up work to commit 3c3b8a4b26, which taught VACUUM to truncate the
line pointer array in about the same way during VACUUM's second pass
over the heap.  We now apply line pointer array truncation during both
the first and the second pass over the heap made by VACUUM.  We can also
perform line pointer array truncation during opportunistic pruning.

Matthias van de Meent, with small tweaks by me.

Author: Matthias van de Meent <boekewurm+postgres@gmail.com>
Discussion: https://postgr.es/m/CAEze2WjgaQc55Y5f5CQd3L=eS5CZcff2Obxp=O6pto8-f0hC4w@mail.gmail.com
Discussion: https://postgr.es/m/CAEze2Wg36%2B4at2eWJNcYNiW2FJmht34x3YeX54ctUSs7kKoNcA%40mail.gmail.com
2022-04-07 15:42:12 -07:00
David Rowley 9d9c02ccd1 Teach planner and executor about monotonic window funcs
Window functions such as row_number() always return a value higher than
the previously returned value for tuples in any given window partition.

Traditionally queries such as;

SELECT * FROM (
   SELECT *, row_number() over (order by c) rn
   FROM t
) t WHERE rn <= 10;

were executed fairly inefficiently.  Neither the query planner nor the
executor knew that once rn made it to 11 that nothing further would match
the outer query's WHERE clause.  It would blindly continue until all
tuples were exhausted from the subquery.

Here we implement means to make the above execute more efficiently.

This is done by way of adding a pg_proc.prosupport function to various of
the built-in window functions and adding supporting code to allow the
support function to inform the planner if the window function is
monotonically increasing, monotonically decreasing, both or neither.  The
planner is then able to make use of that information and possibly allow
the executor to short-circuit execution by way of adding a "run condition"
to the WindowAgg to allow it to determine if some of its execution work
can be skipped.

This "run condition" is not like a normal filter.  These run conditions
are only built using quals comparing values to monotonic window functions.
For monotonic increasing functions, quals making use of the btree
operators for <, <= and = can be used (assuming the window function column
is on the left). You can see here that once such a condition becomes false
that a monotonic increasing function could never make it subsequently true
again.  For monotonically decreasing functions the >, >= and = btree
operators for the given type can be used for run conditions.

The best-case situation for this is when there is a single WindowAgg node
without a PARTITION BY clause.  Here when the run condition becomes false
the WindowAgg node can simply return NULL.  No more tuples will ever match
the run condition.  It's a little more complex when there is a PARTITION
BY clause.  In this case, we cannot return NULL as we must still process
other partitions.  To speed this case up we pull tuples from the outer
plan to check if they're from the same partition and simply discard them
if they are.  When we find a tuple belonging to another partition we start
processing as normal again until the run condition becomes false or we run
out of tuples to process.

When there are multiple WindowAgg nodes to evaluate then this complicates
the situation.  For intermediate WindowAggs we must ensure we always
return all tuples to the calling node.  Any filtering done could lead to
incorrect results in WindowAgg nodes above.  For all intermediate nodes,
we can still save some work when the run condition becomes false.  We've
no need to evaluate the WindowFuncs anymore.  Other WindowAgg nodes cannot
reference the value of these and these tuples will not appear in the final
result anyway.  The savings here are small in comparison to what can be
saved in the top-level WingowAgg, but still worthwhile.

Intermediate WindowAgg nodes never filter out tuples, but here we change
WindowAgg so that the top-level WindowAgg filters out tuples that don't
match the intermediate WindowAgg node's run condition.  Such filters
appear in the "Filter" clause in EXPLAIN for the top-level WindowAgg node.

Here we add prosupport functions to allow the above to work for;
row_number(), rank(), dense_rank(), count(*) and count(expr).  It appears
technically possible to do the same for min() and max(), however, it seems
unlikely to be useful enough, so that's not done here.

Bump catversion

Author: David Rowley
Reviewed-by: Andy Fan, Zhihong Yu
Discussion: https://postgr.es/m/CAApHDvqvp3At8++yF8ij06sdcoo1S_b2YoaT9D4Nf+MObzsrLQ@mail.gmail.com
2022-04-08 10:34:36 +12:00