statext_is_compatible_clause_internal() checked that the arguments
of a ScalarArrayOpExpr are one Var and one Const, but it would allow
cases where the Const was on the left. Subsequent uses of the clause
are not expecting that and would suffer assertion failures or core
dumps. mcv.c also had not bothered to cope with the case of a NULL
array constant, which seems really unacceptably sloppy of somebody.
(Although our tools failed us there too, since AFAIK neither Coverity
nor any compiler warned of the obvious use-of-uninitialized-variable
condition.) It seems best to handle that by having
statext_is_compatible_clause_internal() reject it.
Noted while fixing bug #17570. Back-patch to v13 where the
extended stats code grew some awareness of ScalarArrayOpExpr.
This makes it more convenient for git config to contain the
blame.ignoreRevsFile setting; otherwise current git versions complain if
the file is not present.
I constructed the file for each branch by scraping the file in branch
master for commits that appear in that branch. Because a few additional
pgindent commits have been added to the list in master since the list
was first created, this also propagates those to branches 14 and 15
where the file already existed. Also, some entries appear to have been
made using author-date rather than committer-date in the format string,
so some timestamps are changed. Also remove bogus whitespace in the
suggested `git log` format string.
Backpatch to all supported branches.
Discussion: https://postgr.es/m/20220711163138.o72evdeus5f5yy5z@alvherre.pgsql
Commit a4d75c86b improved the extended-stats logic to allow extended
stats to be collected on expressions not just bare Vars. To apply
such stats, we first verify that the user has permissions to read all
columns used in the stats. (If not, the query will likely fail at
runtime, but the planner ought not do so.) That had to get extended
to check permissions of columns appearing within such expressions,
but the code for that was completely wrong: it applied pull_varattnos
to the wrong pointer, leading to "unrecognized node type" failures.
Furthermore, although you couldn't get to this because of that bug,
it failed to account for the attnum offset applied by pull_varattnos.
This escaped recognition so far because the code in question is not
reached when the user has whole-table SELECT privilege (which is the
common case), and because only subexpressions not specially handled
by statext_is_compatible_clause_internal() are at risk.
I think a large part of the reason for this bug is under-documentation
of what statext_is_compatible_clause() is doing and what its arguments
are, so do some work on the comments to try to improve that.
Per bug #17570 from Alexander Kozhemyakin. Patch by Richard Guo;
comments and other cosmetic improvements by me. (Thanks also to
Japin Li for diagnosis.) Back-patch to v14 where the bug came in.
Discussion: https://postgr.es/m/17570-f2f2e0f4bccf0965@postgresql.org
Having additional triggers in a test table made the ORDER BY clauses in
old queries underspecified. Add another column there for stability.
Per sporadic buildfarm pink.
When inserting a view referencing a foreign table that has WITH CHECK
OPTION constraints, in single-insert mode postgres_fdw retrieves the
data that was actually inserted on the remote side so that the WITH
CHECK OPTION constraints are enforced with the data locally, but in
batch-insert mode it cannot currently retrieve the data (except for the
row first inserted through the view), resulting in enforcing the WITH
CHECK OPTION constraints with the data passed from the core (except for
the first-inserted row), which led to incorrect results when inserting
into a view referencing a foreign table in which a remote BEFORE ROW
INSERT trigger changes the rows inserted through the view so that they
violate the view's WITH CHECK OPTION constraint. Also, the query
inserting into the view caused an assertion failure in assert-enabled
builds.
Fix these by disabling batch insertion when inserting into such a view.
Back-patch to v14 where batch insertion was added.
Discussion: https://postgr.es/m/CAPmGK17LpbTZs4m4a_6THP54UBeK9fHvX8aVVA%2BC6yEZDZwQcg%40mail.gmail.com
Using ATSimpleRecursion() in ATPrepCmd() to do so as bbb927b4db did is
not correct, because ATPrepCmd() can't distinguish between triggers that
may be cloned and those that may not, so would wrongly try to recurse
for the latter category of triggers.
So this commit restores the code in EnableDisableTrigger() that
86f575948c had added to do the recursion, which would do it only for
triggers that may be cloned, that is, row-level triggers. This also
changes tablecmds.c such that ATExecCmd() is able to pass the value of
ONLY flag down to EnableDisableTrigger() using its new 'recurse'
parameter.
This also fixes what seems like an oversight of 86f575948c that the
recursion to partition triggers would only occur if EnableDisableTrigger()
had actually changed the trigger. It is more apt to recurse to inspect
partition triggers even if the parent's trigger didn't need to be
changed: only then can we be certain that all descendants share the same
state afterwards.
Backpatch all the way back to 11, like bbb927b4db. Care is taken not
to break ABI compatibility (and that no catversion bump is needed.)
Co-authored-by: Amit Langote <amitlangote09@gmail.com>
Reviewed-by: Dmitry Koval <d.koval@postgrespro.ru>
Discussion: https://postgr.es/m/CA+HiwqG-cZT3XzGAnEgZQLoQbyfJApVwOTQaCaas1mhpf+4V5A@mail.gmail.com
clock_gettime() is in SUSv2 and all targeted Unix systems have it.
Remove a chunk of fallback code for old Unix is no longer reachable on
modern systems, and untested as of the retirement of build farm animal
prairiedog.
There is no need to retain a HAVE_CLOCK_GETTIME macro here, because it
is already used in a context with Unix and Windows code paths.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CA+hUKGJ3LHeP9w5Fgzdr4G8AnEtJ=z=p6hGDEm4qYGEUX5B6fQ@mail.gmail.com
Commit dd299df818, which made heap TID a tiebreaker nbtree index
column, introduced new rules on page space management to make suffix
truncation safe for v4+ indexes. New pivot tuples (generated by suffix
truncation during leaf page splits) sometimes require dedicated extra
space at the end of a new leaf page high key/pivot to store a heap TID
using a special representation (a representation only used in pivot
tuples).
The definition of "1/3 of a page" was reduced by a single MAXALIGN()
quantum for v4 indexes to make sure that the final enlarged pivot tuple
always fit, even with a split point whose firstright tuple happened to
already be at the "1/3 of a page" limit (limit for non-pivot tuples).
Internal pages (which only contain pivot tuples) stuck with the original
"1/3 of a page" definition. This scheme made it impossible for any page
split to fail to free enough space for its newitem, which is never okay.
The macro that determines whether non-pivot tuples exceed their "1/3 of
a leaf page" restriction was structured as if space was needed for all
three tuples during a leaf page split (the new pivot plus two very large
adjoining non-pivots that are separated by the split). This was subtly
wrong, in that it accidentally relied on implementation details that
could (at least in theory) change in the future.
To fix, make the macro subtract a single MAXALIGN() quantum, once. The
macro evaluates to exactly the same value as before in practice. But it
no longer depends on the current layout of nbtree's special area struct.
No backpatch, since this isn't a live bug.
Author: Peter Geoghegan <pg@bowt.ie>
Reported-By: Robert Haas <robertmhaas@gmail.com>
Diagnosed-By: Robert Haas <robertmhaas@gmail.com>
Discussion: https://postgr.es/m/CA+Tgmoa7UBxivM7f6Ocx_qbq4=ky3uXc+WZNOBcVX+kvJvWOEA@mail.gmail.com
preadv() and pwritev() are not standardized by POSIX, but appeared in
NetBSD in 1999 and were adopted by at least OpenBSD, FreeBSD,
DragonFlyBSD, Linux, AIX, illumos and macOS. We don't use them much
yet, but an active proposal uses them heavily.
In 15, we had two replacement implementations for other OSes: one based
on lseek() + -v function if available for true vector I/O, and the other
based on a loop over p- function.
The former would be an obstacle to hypothetical future multi-threaded
code sharing file descriptors, while the latter would not, since commit
cf112c12. Furthermore, the number of targeted systems that could
benefit from the former's potential upside has dwindled to just one
niche OS, since macOS added the functions and we de-supported HP-UX.
That doesn't seem like a good trade-off.
Therefore, drop the lseek()-based variant, and also the pg_ prefix now
that the file position portability hazard is gone.
At the time of writing, the only systems in our build farm that lack
native preadv/pwritev and thus use fallback code are:
* Solaris (but not illumos)
* macOS before release 11.0
* Windows
With this commit, the above systems will now use the *same* fallback
code, the version that loops over pread()/pwrite(). Windows already
used that (though a later proposal may include true vector I/O for
Windows), so this decision really only affects Solaris, until it gets
around to adding these system calls.
Also remove some useless includes while here.
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CA+hUKGJ3LHeP9w5Fgzdr4G8AnEtJ=z=p6hGDEm4qYGEUX5B6fQ@mail.gmail.com
This commit adjusts two log messages:
- When a field in pg_ident.conf is not populated, report the line of the
configuration file in an error context message instead of the main
entry.
- When parsing pg_ident.conf and finding an invalid regexp, add some
information about the line of the configuration file involved within an
error context message.
Author: Julien Rouhaud
Discussion: https://postgr.es/m/20220223045959.35ipdsvbxcstrhya@jrouhaud
This is particularly useful when log_min_messages is set to FATAL, so as
one can know which file was not getting loaded whether hba_file or
ident_file are set to some non-default values. If using the default
values of these GUC parameters, the same reports are generated.
This commit changes the load (startup) and reload (SIGHUP) messages.
Author: Julien Rouhaud
Discussion: https://postgr.es/m/20220223045959.35ipdsvbxcstrhya@jrouhaud
pread() and pwrite() are in SUSv2, and all targeted Unix systems have
them.
Previously, we defined pg_pread and pg_pwrite to emulate these function
with lseek() on old Unixen. The names with a pg_ prefix were a reminder
of a portability hazard: they might change the current file position.
That hazard is gone, so we can drop the prefixes.
Since the remaining replacement code is Windows-only, move it into
src/port/win32p{read,write}.c, and move the declarations into
src/include/port/win32_port.h.
No need for vestigial HAVE_PREAD, HAVE_PWRITE macros as they were only
used for declarations in port.h which have now moved into win32_port.h.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Greg Stark <stark@mit.edu>
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CA+hUKGJ3LHeP9w5Fgzdr4G8AnEtJ=z=p6hGDEm4qYGEUX5B6fQ@mail.gmail.com
setenv() and unsetenv() are in SUSv3 and targeted Unix systems have
them. We still need special code for these on Windows, but that doesn't
require a configure probe.
This marks the first time we require a SUSv3 (POSIX.1-2001) facility
(rather than SUSv2). The replacement code removed here was not needed
on any targeted system or any known non-EOL'd Unix system, and was
therefore dead and untested.
No need for vestigial HAVE_SETENV and HAVE_UNSETENV macros, because we
provide a replacement for Windows, and we didn't previously test the
macros.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Greg Stark <stark@mit.edu>
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CA+hUKGJ3LHeP9w5Fgzdr4G8AnEtJ=z=p6hGDEm4qYGEUX5B6fQ@mail.gmail.com
poll() and <poll.h> are in SUSv2 and all targeted Unix systems have
them.
Retain HAVE_POLL and HAVE_POLL_H macros for readability. There's an
error in latch.c that is now unreachable (since we always have one of
WIN32 or HAVE_POLL defined), but that falls out of a decision to keep
using defined(HAVE_POLL) instead of !defined(WIN32) to guard the poll()
code.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CA+hUKGJ3LHeP9w5Fgzdr4G8AnEtJ=z=p6hGDEm4qYGEUX5B6fQ@mail.gmail.com
link() is in SUSv2 and all targeted Unix systems have it. We have
replacement code for Windows that doesn't require a configure probe.
Since only Windows needs it, rename src/port/link.c to win32link.c like
other similar things.
There is no need for a vestigial HAVE_LINK macro, because we expect all
Unix and, with our replacement function, Windows systems to have it, so
we didn't have any tests around link() usage.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CA+hUKGJ3LHeP9w5Fgzdr4G8AnEtJ=z=p6hGDEm4qYGEUX5B6fQ@mail.gmail.com
symlink() and readlink() are in SUSv2 and all targeted Unix systems have
them. We have partial emulation on Windows. Code that raised runtime
errors on systems without it has been dead for years, so we can remove
that and also references to such systems in the documentation.
Define HAVE_READLINK and HAVE_SYMLINK macros on Unix. Our Windows
replacement functions based on junction points can't be used for
relative paths or for non-directories, so the macros can be used to
check for full symlink support. The places that deal with tablespaces
can just use symlink functions without checking the macros. (If they
did check the macros, they'd need to provide an #else branch with a
runtime or compile time error, and it'd be dead code.)
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CA+hUKGJ3LHeP9w5Fgzdr4G8AnEtJ=z=p6hGDEm4qYGEUX5B6fQ@mail.gmail.com
setsid() is in SUSv2 and all targeted Unix systems have it. Retain a
HAVE_SETSID macro, defined on Unix only. That's easier to understand
than !defined(WIN32), for the optional code it governs.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CA+hUKGJ3LHeP9w5Fgzdr4G8AnEtJ=z=p6hGDEm4qYGEUX5B6fQ@mail.gmail.com
shm_open() is in SUSv2 and all targeted Unix systems have it.
We retain a HAVE_SHM_OPEN macro, because it's clearer to readers than
something like !defined(WIN32).
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CA+hUKGJ3LHeP9w5Fgzdr4G8AnEtJ=z=p6hGDEm4qYGEUX5B6fQ@mail.gmail.com
getrlimit() is in SUSv2 and all targeted systems have it.
Windows doesn't have it. We could just use #ifndef WIN32, but for a
little more explanation about why we're making things conditional, let's
retain the HAVE_GETRLIMIT macro. It's defined in port.h for Unix systems.
On systems that have it, it's not necessary to test for RLIMIT_CORE,
RLIMIT_STACK or RLIMIT_NOFILE macros, since SUSv2 requires those and all
targeted systems have them. Also remove references to a pre-historic
alternative spelling of RLIMIT_NOFILE, and coding that seemed to believe
that Cygwin didn't have it.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CA+hUKGJ3LHeP9w5Fgzdr4G8AnEtJ=z=p6hGDEm4qYGEUX5B6fQ@mail.gmail.com
dlopen() is in SUSv2 and all targeted Unix systems have it. We still
need replacement functions for Windows, but we don't need a configure
probe for that.
Since it's no longer needed by other operating systems, rename dlopen.c
to win32dlopen.c and move the declarations into win32_port.h.
Likewise, the macros RTLD_NOW and RTLD_GLOBAL now only need to be
defined on Windows, since all targeted Unix systems have 'em.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CA+hUKGJ3LHeP9w5Fgzdr4G8AnEtJ=z=p6hGDEm4qYGEUX5B6fQ@mail.gmail.com
The test is proving to be unreliable in the buildfarm, and we neither
agree on how best to fix it nor have time to do so before the upcoming
release. So for now, put things back to the way they were before commit
d498e052b4.
Discussion: http://postgr.es/m/3628089.1659640252@sss.pgh.pa.us
Adjusting this function was overlooked in commit 94aa7cc5f. The only
visible symptom (so far) is that INSERT ... ON CONFLICT could go into
an endless loop when inserting a null that has a conflict.
Richard Guo and Tom Lane, per bug #17558 from Andrew Kesper
Discussion: https://postgr.es/m/17558-3f6599ffcf52fd4a@postgresql.org
Ordinarily the functions called in this loop ought to have plenty
of CFIs themselves; but we've now seen a case where no such CFI is
reached, making the loop uninterruptible. Even though that's from
a recently-introduced bug, it seems prudent to install a CFI at
the loop level in all branches.
Per discussion of bug #17558 from Andrew Kesper (an actual fix for
that bug will follow).
Discussion: https://postgr.es/m/17558-3f6599ffcf52fd4a@postgresql.org
Remove the test case added by commit fac1b470a, which never actually
worked to expose the problem it claimed to test. Replace it with
a case that does expose the problem, and also covers the SRF-not-
at-the-top deficiency repaired in 1aa8dad41.
Richard Guo, with some editorialization by me
Discussion: https://postgr.es/m/17564-c7472c2f90ef2da3@postgresql.org
The use of "we" when referring to the active backend might be
misunderstood, so rephrase to make it clearer who is performing
the actions discussed in the comment.
Author: Junwang Zhao <zhjwpku@gmail.com>
Reviewed-by: Erikjan Rijkers <er@xs4all.nl>
Reviewed-by: Robert Treat <rob@xzilla.net>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/CAEG8a3LRSMqkvjiURiJoSi4aGWORpiXUmUfQQK5PaD6WfPzu3w@mail.gmail.com
SSE2 vector instructions are part of the spec for the 64-bit x86
architecture. Until now we have relied on the compiler to autovectorize
in some limited situations, but some useful coding idioms can only be
expressed explicitly via compiler intrinsics. To this end, add a header
that defines USE_SSE2 where available. While x86-only for now, we can
add other architectures in the future. This will also be the intended
place for helper functions that use vector operations.
Reviewed by Nathan Bossart and Masahiko Sawada
Discussion: https://www.postgresql.org/message-id/CAFBsxsE2G_H_5Wbw%2BNOPm70-BK4xxKf86-mRzY%3DL2sLoQqM%2B-Q%40mail.gmail.com
Commit fac1b470a thought we could check for set-returning functions
by testing only the top-level node in an expression tree. This is
wrong in itself, and to make matters worse it encouraged others
to make the same mistake, by exporting tlist.c's special-purpose
IS_SRF_CALL() as a widely-visible macro. I can't find any evidence
that anyone's taken the bait, but it was only a matter of time.
Use expression_returns_set() instead, and stuff the IS_SRF_CALL()
genie back in its bottle, this time with a warning label. I also
added a couple of cross-reference comments.
After a fair amount of fooling around, I've despaired of making
a robust test case that exposes the bug reliably, so no test case
here. (Note that the test case added by fac1b470a is itself
broken, in that it doesn't notice if you remove the code change.
The repro given by the bug submitter currently doesn't fail either
in v15 or HEAD, though I suspect that may indicate an unrelated bug.)
Per bug #17564 from Martijn van Oosterhout. Back-patch to v13,
as the faulty patch was.
Discussion: https://postgr.es/m/17564-c7472c2f90ef2da3@postgresql.org
The sto_using_cursor and sto_using_select tests were coded to exercise
every permutation of their test steps, but AFAICS there is no value in
exercising more than one. This matters because each permutation costs
about six seconds, thanks to the "pg_sleep(6)". Perhaps we could
reduce that, but the useless permutations seem worth getting rid of
in any case. (Note that sto_using_hash_index got it right already.)
While here, clean up some other sloppiness such as an unused table.
This doesn't make too much difference in interactive testing, since the
wasted time is typically masked by parallelization with other tests.
However, the buildfarm runs this as a serial step, which means we can
expect to shave ~40 seconds from every buildfarm run. That makes it
worth back-patching.
Discussion: https://postgr.es/m/2515192.1659454702@sss.pgh.pa.us
The TAP tests for logical replication in src/test/subscription are using
the following code in many places to make sure that the subscription is
synchronized with the publisher:
$node_publisher->wait_for_catchup('tap_sub');
$node_subscriber->poll_query_until('postgres',
qq[SELECT count(1) = 0
FROM pg_subscription_rel
WHERE srsubstate NOT IN ('r', 's')]);
The new function wait_for_subscription_sync() can be used to replace the
above code. This eliminates duplicated code and makes it easier to write
future tests.
Author: Masahiko Sawada
Reviewed by: Amit Kapila, Shi yu
Discussion: https://postgr.es/m/CAD21AoC-fvAkaKHa4t1urupwL8xbAcWRePeETvshvy80f6WV1A@mail.gmail.com
We've heard a couple of reports of people having trouble with
multi-gigabyte-sized query-texts files. It occurred to me that on
32-bit platforms, there could be an issue with integer overflow
of calculations associated with the total query text size.
Address that with several changes:
1. Limit pg_stat_statements.max to INT_MAX / 2 not INT_MAX.
The hashtable code will bound it to that anyway unless "long"
is 64 bits. We still need overflow guards on its use, but
this helps.
2. Add a check to prevent extending the query-texts file to
more than MaxAllocHugeSize. If it got that big, qtext_load_file
would certainly fail, so there's not much point in allowing it.
Without this, we'd need to consider whether extent, query_offset,
and related variables shouldn't be off_t not size_t.
3. Adjust the comparisons in need_gc_qtexts() to be done in 64-bit
arithmetic on all platforms. It appears possible that under duress
those multiplications could overflow 32 bits, yielding a false
conclusion that we need to garbage-collect the texts file, which
could lead to repeatedly garbage-collecting after every hash table
insertion.
Per report from Bruno da Silva. I'm not convinced that these
issues fully explain his problem; there may be some other bug that's
contributing to the query-texts file becoming so large in the first
place. But it did get that big, so #2 is a reasonable defense,
and #3 could explain the reported performance difficulties.
(See also commit 8bbe4cbd9, which addressed some related bugs.
The second Discussion: link is the thread that led up to that.)
This issue is old, and is primarily a problem for old platforms,
so back-patch.
Discussion: https://postgr.es/m/CAB+Nuk93fL1Q9eLOCotvLP07g7RAv4vbdrkm0cVQohDVMpAb9A@mail.gmail.com
Discussion: https://postgr.es/m/5601D354.5000703@BlueTreble.com
Previously, a byte with the high bit set was just transmitted
as-is by charin() and charout(). This is problematic if the
database encoding is multibyte, because the result of charout()
won't be validly encoded, which breaks various stuff that
expects all text strings to be validly encoded. We've
previously decided to enforce encoding validity rather than try
to individually harden each place that might have a problem with
such strings, so it's time to do something about "char".
To fix, represent high-bit-set characters as \ooo (backslash
and three octal digits), following the ancient "escape" format
for bytea. charin() will continue to accept the old way as well,
though that is only reachable in single-byte encodings.
Add some test cases just so there is coverage for this code.
We'll otherwise leave this question undocumented as it was before,
because we don't really want to encourage end-user use of "char".
For the moment, back-patch into v15 so that this change appears
in 15beta3. If there's not great pushback we should consider
absorbing this change into the older branches.
Discussion: https://postgr.es/m/2318797.1638558730@sss.pgh.pa.us
ORDER BY / DISTINCT aggreagtes have, since implemented in Postgres, been
executed by always performing a sort in nodeAgg.c to sort the tuples in
the current group into the correct order before calling the transition
function on the sorted tuples. This was not great as often there might be
an index that could have provided pre-sorted input and allowed the
transition functions to be called as the rows come in, rather than having
to store them in a tuplestore in order to sort them once all the tuples
for the group have arrived.
Here we change the planner so it requests a path with a sort order which
supports the most amount of ORDER BY / DISTINCT aggregate functions and
add new code to the executor to allow it to support the processing of
ORDER BY / DISTINCT aggregates where the tuples are already sorted in the
correct order.
Since there can be many ORDER BY / DISTINCT aggregates in any given query
level, it's very possible that we can't find an order that suits all of
these aggregates. The sort order that the planner chooses is simply the
one that suits the most aggregate functions. We take the most strictly
sorted variation of each order and see how many aggregate functions can
use that, then we try again with the order of the remaining aggregates to
see if another order would suit more aggregate functions. For example:
SELECT agg(a ORDER BY a),agg2(a ORDER BY a,b) ...
would request the sort order to be {a, b} because {a} is a subset of the
sort order of {a,b}, but;
SELECT agg(a ORDER BY a),agg2(a ORDER BY c) ...
would just pick a plan ordered by {a} (we give precedence to aggregates
which are earlier in the targetlist).
SELECT agg(a ORDER BY a),agg2(a ORDER BY b),agg3(a ORDER BY b) ...
would choose to order by {b} since two aggregates suit that vs just one
that requires input ordered by {a}.
Author: David Rowley
Reviewed-by: Ronan Dunklau, James Coleman, Ranier Vilela, Richard Guo, Tom Lane
Discussion: https://postgr.es/m/CAApHDvpHzfo92%3DR4W0%2BxVua3BUYCKMckWAmo-2t_KiXN-wYH%3Dw%40mail.gmail.com
The select_outer_pathkeys_for_merge function made an attempt to build the
merge join pathkeys in the same order as query_pathkeys. This was done as
it may have led to no sort being required for an ORDER BY or GROUP BY
clause in the upper planner. However, this restriction seems overly
strict as it required that we match the query_pathkeys entirely or we
don't bother putting the merge join pathkeys in that order.
Here we relax this rule so that we use a prefix of the query_pathkeys
providing that prefix matches all of the join quals. This may provide the
upper planner with partially sorted input which will allow the use of
incremental sorts instead of full sorts.
Author: David Rowley
Reviewed-by: Richard Guo
Discussion: https://postgr.es/m/CAApHDvrtZu0PHVfDPFM4Yx3jNR2Wuwosv+T2zqa7LrhhBr2rRg@mail.gmail.com
Tom Lane