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
Here we add code which detects when ExecFindPartition() continually finds
the same partition and add a caching layer to improve partition lookup
performance for such cases.
Both RANGE and LIST partitioned tables traditionally require a binary
search for the set of Datums that a partition needs to be found for. This
binary search is commonly visible in profiles when bulk loading into a
partitioned table. Here we aim to reduce the overhead of bulk-loading
into partitioned tables for cases where many consecutive tuples belong to
the same partition and make the performance of this operation closer to
what it is with a traditional non-partitioned table.
When we find the same partition 16 times in a row, the next search will
result in us simply just checking if the current set of values belongs to
the last found partition. For LIST partitioning we record the index into
the PartitionBoundInfo's datum array. This allows us to check if the
current Datum is the same as the Datum that was last looked up. This
means if any given LIST partition supports storing multiple different
Datum values, then the caching only works when we find the same value as
we did the last time. For RANGE partitioning we simply check if the given
Datums are in the same range as the previously found partition.
We store the details of the cached partition in PartitionDesc (i.e.
relcache) so that the cached values are maintained over multiple
statements.
No caching is done for HASH partitions. The majority of the cost in HASH
partition lookups are in the hashing function(s), which would also have to
be executed if we were to try to do caching for HASH partitioned tables.
Since most of the cost is already incurred, we just don't bother. We also
don't do any caching for LIST partitions when we continually find the
values being looked up belong to the DEFAULT partition. We've no
corresponding index in the PartitionBoundInfo's datum array for this case.
We also don't cache when we find the given values match to a LIST
partitioned table's NULL partition. This is so cheap that there's no
point in doing any caching for this. We also don't cache for a RANGE
partitioned table's DEFAULT partition.
There have been a number of different patches submitted to improve
partition lookups. Hou, Zhijie submitted a patch to detect when the value
belonging to the partition key column(s) were constant and added code to
cache the partition in that case. Amit Langote then implemented an idea
suggested by me to remember the last found partition and start to check if
the current values work for that partition. The final patch here was
written by me and was done by taking many of the ideas I liked from the
patches in the thread and redesigning other aspects.
Discussion: https://postgr.es/m/OS0PR01MB571649B27E912EA6CC4EEF03942D9%40OS0PR01MB5716.jpnprd01.prod.outlook.com
Author: Amit Langote, Hou Zhijie, David Rowley
Reviewed-by: Amit Langote, Hou Zhijie
I thought commit fd96d14d9 had plugged all the holes of this sort,
but no, function RTEs could produce oversize tuples too, either
via long coldeflists or just from multiple functions in one RTE.
(I'm pretty sure the other variants of base RTEs aren't a problem,
because they ultimately refer to either a table or a sub-SELECT,
whose widths are enforced elsewhere. But we explicitly allow join
RTEs to be overwidth, as long as you don't try to form their
tuple result.)
Per further discussion of bug #17561. As before, patch all branches.
Discussion: https://postgr.es/m/17561-80350151b9ad2ad4@postgresql.org
errno was not reported correctly after attempting to clone a file,
leading to incorrect error reports. While scanning through the code, I
have not noticed any similar mistakes.
Error introduced in 3a769d8.
Author: Justin Pryzby
Discussion: https://postgr.es/m/20220731134135.GY15006@telsasoft.com
Backpatch-through: 12
This commit adds some test coverage for ee79647 (prevent BASE_BACKUP
from running in the middle of another base backup) and b24b2be
(BASE_BACKUP cancellation followed by pg_backup_start), caused by the
interactions of replication and SQL commands in a logical replication
connection in a WAL sender.
The second test uses a design close to what has been introduced in
0475a97f, where BASE_BACKUP is throttled to give enough room for a
cancellation, though this time we rely on psql with multiple -c
switches to keep a connection around for the second query.
Reviewed-by: Fujii Masao
Discussion: https://postgr.es/m/Ys/NCI4Eo9300GnQ@paquier.xyz
In the short time this function has existed, it's already proven to be
a nontrivial maintenance burden, since it has to be updated whenever a
node tag is added or removed. Although in principle we could now
automate that, I see little justification for having such functionality
here at all. The function is only being applied to utility statements,
for which we already have infrastructure for obtaining string names.
Moreover, that infrastructure produces already-familiar-to-users names,
unlike nodetag_to_string().
So, remove this function and use the existing infrastructure instead.
That saves over a thousand lines of largely-unreachable code.
Back-patch to v15 where this code came in. Although it seems unlikely
that v15's nodetag list will change anymore, we might as well keep the
two branches looking and acting alike; otherwise back-patching any
test-results changes in this area will be painful.
Discussion: https://postgr.es/m/843818.1659218928@sss.pgh.pa.us
These two new options can be used to either process all tables in
specific schemas or to skip processing all tables in specific
schemas. This change also refactors the handling of invalid
combinations of command-line options to a new helper function.
Author: Gilles Darold
Reviewed-by: Justin Pryzby, Nathan Bossart and Michael Paquier.
Discussion: https://postgr.es/m/929fbf3c-24b8-d454-811f-1d5898ab3e91%40migops.com
freebsd 13.0 is out of support, switch to 13.1. It might be a good idea to
remove the minor version number from the image name, but there's not been a
response to that so far...
Discussion: https://postgr.es/m/20220728095704.ryywoaz4dqqrwstc@alap3.anarazel.de
Backpatch: 15-, just like the CI support
The code tried to access ARR_DIMS(v)[0] and ARR_LBOUND(v)[0]
whether or not those values exist. This made the range check
on the "n" argument unstable --- it might or might not fail, and
if it did it would report garbage for the allowed upper limit.
These bogus accesses would probably annoy Valgrind, and if you
were very unlucky even lead to SIGSEGV.
Report and fix by Martin Kalcher. Back-patch to v14 where this
function was added.
Discussion: https://postgr.es/m/baaeb413-b8a8-4656-5757-ef347e5ec11f@aboutsource.net
These flavors of ALTER TABLE were already shaped to report the
ObjectAddress of the partition attached or detached, but this data was
not added to what is collected for event triggers. The tests of
test_ddl_deparse are updated to show the modification in the data
reported.
Author: Hou Zhijie
Reviewed-by: Álvaro Herrera, Amit Kapila, Hayato Kuroda, Michael Paquier
Discussion: https://postgr.es/m/OS0PR01MB571626984BD099DADF53F38394899@OS0PR01MB5716.jpnprd01.prod.outlook.com
This module is expanded to track the description of the objects changed
in the subcommands of ALTER TABLE by reworking the function
get_altertable_subcmdtypes() (now named get_altertable_subcmdinfo) used
in the event trigger of the test. It now returns a set of rows made of
(subcommand type, object description) instead of a text array with only
the information about the subcommand type.
The tests have been lacking a lot of the subcommands added to
AlterTableType over the years. All the missing subcommands are added,
and the code is now structured so as the addition of a new subcommand
is detected by removing the default clause used in the switch for the
subcommand types.
The coverage of the module is increased from roughly 30% to 50%. More
could be done but this is already a nice improvement.
Author: Michael Paquier, Hou Zhijie
Reviewed-by: Álvaro Herrera, Amit Kapila, Hayato Kuroda
Discussion: https://postgr.es/m/OS0PR01MB571626984BD099DADF53F38394899@OS0PR01MB5716.jpnprd01.prod.outlook.com
We can't check the output of this view very closely without
creating portability headaches, but we can make sure that
the number of rows is as-expected. In any case, this is
sufficient to exercise all the C code within, which is a
lot better than the 0% coverage we had before.
DongWook Lee
Discussion: https://postgr.es/m/CAAcByaLCHGJB7qAENEcx9D09UL=w4ma+yijwF_-1MSqQZ9wK6Q@mail.gmail.com
Two callers of generate_useful_gather_paths were testing the wrong
thing when deciding whether to call that function: they checked for
being at the top of the current join subproblem, rather than being at
the actual top join. This'd result in failing to construct parallel
paths for a sub-join for which they might be useful.
While set_rel_pathlist() isn't actively broken, it seems best to
make its identical-in-intention test for this be like the other two.
This has been wrong all along, but given the lack of field complaints
I'm hesitant to back-patch into stable branches; we usually prefer
to avoid non-bug-fix changes in plan choices in minor releases.
It seems not too late for v15 though.
Richard Guo, reviewed by Antonin Houska and Tom Lane
Discussion: https://postgr.es/m/CAMbWs4-mH8Zf87-w+3P2J=nJB+5OyicO28ia9q_9o=Lamf_VHg@mail.gmail.com
Thomas Munro