This allows the compiler / linker to mark affected pages as read-only.
There's other cases, but they're a bit more invasive, and should go
through some review. These are easy.
They were found with
objdump -j .data -t src/backend/postgres|awk '{print $4, $5, $6}'|sort -r|less
Discussion: https://postgr.es/m/20181015200754.7y7zfuzsoux2c4ya@alap3.anarazel.de
On a primary, sets of XLOG_RUNNING_XACTS records are generated on a
periodic basis to allow recovery to build the initial state of
transactions for a hot standby. The set of transaction IDs is created
by scanning all the entries in ProcArray. However it happens that its
logic never counted on the fact that two-phase transactions finishing to
prepare can put ProcArray in a state where there are two entries with
the same transaction ID, one for the initial transaction which gets
cleared when prepare finishes, and a second, dummy, entry to track that
the transaction is still running after prepare finishes. This way
ensures a continuous presence of the transaction so as callers of for
example TransactionIdIsInProgress() are always able to see it as alive.
So, if a XLOG_RUNNING_XACTS takes a standby snapshot while a two-phase
transaction finishes to prepare, the record can finish with duplicated
XIDs, which is a state expected by design. If this record gets applied
on a standby to initial its recovery state, then it would simply fail,
so the odds of facing this failure are very low in practice. It would
be tempting to change the generation of XLOG_RUNNING_XACTS so as
duplicates are removed on the source, but this requires to hold on
ProcArrayLock for longer and this would impact all workloads,
particularly those using heavily two-phase transactions.
XLOG_RUNNING_XACTS is also actually used only to initialize the standby
state at recovery, so instead the solution is taken to discard
duplicates when applying the initial snapshot.
Diagnosed-by: Konstantin Knizhnik
Author: Michael Paquier
Discussion: https://postgr.es/m/0c96b653-4696-d4b4-6b5d-78143175d113@postgrespro.ru
Backpatch-through: 9.3
This moves the system administration functions for signalling backends
from backend/utils/adt/misc.c into a separate file dedicated to backend
signalling. No new functionality is introduced in this commit.
Author: Daniel Gustafsson
Reviewed-by: Michael Paquier, Álvaro Herrera
Discussion: https://postgr.es/m/C2C7C3EC-CC5F-44B6-9C78-637C88BD7D14@yesql.se
Opening a relation with no lock at all is unsafe; there's no guarantee
that we'll see a consistent state of the relevant catalog entries.
While use of MVCC scans to read the catalogs partially addresses that
complaint, it's still possible to switch to a new catalog snapshot
partway through loading the relcache entry. Moreover, whether or not
you trust the reasoning behind sometimes using less than
AccessExclusiveLock for ALTER TABLE, that reasoning is certainly not
valid if concurrent users of the table don't hold a lock corresponding
to the operation they want to perform.
Hence, add some assertion-build-only checks that require any caller
of relation_open(x, NoLock) to hold at least AccessShareLock. This
isn't a full solution, since we can't verify that the lock level is
semantically appropriate for the action --- but it's definitely of
some use, because it's already caught two bugs.
We can also assert that callers of addRangeTableEntryForRelation()
hold at least the lock level specified for the new RTE.
Amit Langote and Tom Lane
Discussion: https://postgr.es/m/16565.1538327894@sss.pgh.pa.us
Commit 37c54863c removed the code in StandbyAcquireAccessExclusiveLock
that checked the return value of LockAcquireExtended. That created a
bug, because it's still passing reportMemoryError = false to
LockAcquireExtended, meaning that LOCKACQUIRE_NOT_AVAIL will be returned
if we're out of shared memory for the lock table.
In such a situation, the startup process would believe it had acquired an
exclusive lock even though it hadn't, with potentially dire consequences.
To fix, just drop the use of reportMemoryError = false, which allows us
to simplify the call into a plain LockAcquire(). It's unclear that the
locktable-full situation arises often enough that it's worth having a
better recovery method than crash-and-restart. (I strongly suspect that
the only reason the code path existed at all was that it was relatively
simple to do in the pre-37c54863c implementation. But now it's not.)
LockAcquireExtended's reportMemoryError parameter is now dead code and
could be removed. I refrained from doing so, however, because there
was some interest in resurrecting the behavior if we do get reports of
locktable-full failures in the field. Also, it seems unwise to remove
the parameter concurrently with shipping commit f868a8143, which added a
parameter; if there are any third-party callers of LockAcquireExtended,
we want them to get a wrong-number-of-parameters compile error rather
than a possibly-silent misinterpretation of its last parameter.
Back-patch to 9.6 where the bug was introduced.
Discussion: https://postgr.es/m/6202.1536359835@sss.pgh.pa.us
Chris Travers reported that the startup process can repeatedly try to
cancel a backend that is in a posix_fallocate()/EINTR loop and cause it
to loop forever. Teach the retry loop to give up if an interrupt is
pending. Don't actually check for interrupts in that loop though,
because a non-local exit would skip some clean-up code in the caller.
Back-patch to 9.4 where DSM was added (and posix_fallocate() was later
back-patched).
Author: Chris Travers
Reviewed-by: Ildar Musin, Murat Kabilov, Oleksii Kliukin
Tested-by: Oleksii Kliukin
Discussion: https://postgr.es/m/CAN-RpxB-oeZve_J3SM_6%3DHXPmvEG%3DHX%2B9V9pi8g2YR7YW0rBBg%40mail.gmail.com
LockRelationOid and sibling routines supposed that, if our session already
holds the lock they were asked to acquire, they could skip calling
AcceptInvalidationMessages on the grounds that we must have already read
any remote sinval messages issued against the relation being locked.
This is normally true, but there's a critical special case where it's not:
processing inside AcceptInvalidationMessages might attempt to access system
relations, resulting in a recursive call to acquire a relation lock.
Hence, if the outer call had acquired that same system catalog lock, we'd
fall through, despite the possibility that there's an as-yet-unread sinval
message for that system catalog. This could, for example, result in
failure to access a system catalog or index that had just been processed
by VACUUM FULL. This is the explanation for buildfarm failures we've been
seeing intermittently for the past three months. The bug is far older
than that, but commits a54e1f158 et al added a new recursion case within
AcceptInvalidationMessages that is apparently easier to hit than any
previous case.
To fix this, we must not skip calling AcceptInvalidationMessages until
we have *finished* a call to it since acquiring a relation lock, not
merely acquired the lock. (There's already adequate logic inside
AcceptInvalidationMessages to deal with being called recursively.)
Fortunately, we can implement that at trivial cost, by adding a flag
to LOCALLOCK hashtable entries that tracks whether we know we have
completed such a call.
There is an API hazard added by this patch for external callers of
LockAcquire: if anything is testing for LOCKACQUIRE_ALREADY_HELD,
it might be fooled by the new return code LOCKACQUIRE_ALREADY_CLEAR
into thinking the lock wasn't already held. This should be a fail-soft
condition, though, unless something very bizarre is being done in
response to the test.
Also, I added an additional output argument to LockAcquireExtended,
assuming that that probably isn't called by any outside code given
the very limited usefulness of its additional functionality.
Back-patch to all supported branches.
Discussion: https://postgr.es/m/12259.1532117714@sss.pgh.pa.us
There's a project policy against using plain "char buf[BLCKSZ]" local
or static variables as page buffers; preferred style is to palloc or
malloc each buffer to ensure it is MAXALIGN'd. However, that policy's
been ignored in an increasing number of places. We've apparently got
away with it so far, probably because (a) relatively few people use
platforms on which misalignment causes core dumps and/or (b) the
variables chance to be sufficiently aligned anyway. But this is not
something to rely on. Moreover, even if we don't get a core dump,
we might be paying a lot of cycles for misaligned accesses.
To fix, invent new union types PGAlignedBlock and PGAlignedXLogBlock
that the compiler must allocate with sufficient alignment, and use
those in place of plain char arrays.
I used these types even for variables where there's no risk of a
misaligned access, since ensuring proper alignment should make
kernel data transfers faster. I also changed some places where
we had been palloc'ing short-lived buffers, for coding style
uniformity and to save palloc/pfree overhead.
Since this seems to be a live portability hazard (despite the lack
of field reports), back-patch to all supported versions.
Patch by me; thanks to Michael Paquier for review.
Discussion: https://postgr.es/m/1535618100.1286.3.camel@credativ.de
Commit dafa084, added in 10, made the removal of temporary orphaned
tables more aggressive. This commit makes an extra step into the
aggressiveness by adding a flag in each backend's MyProc which tracks
down any temporary namespace currently in use. The flag is set when the
namespace gets created and can be reset if the temporary namespace has
been created in a transaction or sub-transaction which is aborted. The
flag value assignment is assumed to be atomic, so this can be done in a
lock-less fashion like other flags already present in PGPROC like
databaseId or backendId, still the fact that the temporary namespace and
table created are still locked until the transaction creating those
commits acts as a barrier for other backends.
This new flag gets used by autovacuum to discard more aggressively
orphaned tables by additionally checking for the database a backend is
connected to as well as its temporary namespace in-use, removing
orphaned temporary relations even if a backend reuses the same slot as
one which created temporary relations in a past session.
The base idea of this patch comes from Robert Haas, has been written in
its first version by Tsunakawa Takayuki, then heavily reviewed by me.
Author: Tsunakawa Takayuki
Reviewed-by: Michael Paquier, Kyotaro Horiguchi, Andres Freund
Discussion: https://postgr.es/m/0A3221C70F24FB45833433255569204D1F8A4DC6@G01JPEXMBYT05
Backpatch: 11-, as PGPROC gains a new flag and we don't want silent ABI
breakages on already released versions.
When reading an existing FSM or VM page that was found to be corrupt by the
buffer manager, the code applied PageInit() to reinitialize the page, but
did so without any locking. There is thus a hazard that two backends might
concurrently do PageInit, which in itself would still be OK, but the slower
one might then zero over subsequent data changes applied by the faster one.
Even that is unlikely to be fatal; but it's not desirable, so add locking
to prevent it.
This does not add any locking overhead in the normal code path where the
page is OK. It's not immediately obvious that that's safe, but I believe
it is, for reasons explained in the added comments.
Problem noted by R P Asim. It's been like this for a long time, so
back-patch to all supported branches.
Discussion: https://postgr.es/m/CANXE4Te4G0TGq6cr0-TvwP0H4BNiK_-hB5gHe8mF+nz0mcYfMQ@mail.gmail.com
In ad9a274778, shmem_exit_inprogress was
introduced. But we need to reset it after shmem_exit(), because unlike
the similar proc_exit(), shmem_exit() can also be called for cleanup
when the process will not exit.
Reported-by: Andrew Gierth <andrew@tao11.riddles.org.uk>
Header comment of shm_mq.c was mistakenly specifying path to shm_mq.h.
It was introduced in ec9037df. So, theoretically it could be
backpatched to 9.4, but it doesn't seem to worth it.
PostgreSQL nowadays offers some kind of dynamic shared memory feature on
all supported platforms. Having the choice of "none" prevents us from
relying on DSM in core features. So this patch removes the choice of
"none".
Author: Kyotaro Horiguchi <horiguchi.kyotaro@lab.ntt.co.jp>
When multiple relations are deleted at the same transaction,
the files of those relations are deleted by one call to smgrdounlinkall(),
which leads to scan whole shared_buffers only one time. OTOH,
previously, during recovery, smgrdounlink() (not smgrdounlinkall()) was
called for each file to delete, which led to scan shared_buffers
multiple times. Obviously this could cause to increase the WAL replay
time very much especially when shared_buffers was huge.
To alleviate this situation, this commit changes the recovery so that
it also calls smgrdounlinkall() only one time to delete multiple
relation files.
This is just fix for oversight of commit 279628a0a7, not new feature.
So, per discussion on pgsql-hackers, we concluded to backpatch this
to all supported versions.
Author: Fujii Masao
Reviewed-by: Michael Paquier, Andres Freund, Thomas Munro, Kyotaro Horiguchi, Takayuki Tsunakawa
Discussion: https://postgr.es/m/CAHGQGwHVQkdfDqtvGVkty+19cQakAydXn1etGND3X0PHbZ3+6w@mail.gmail.com
Issues relate only to subtransactions that hold AccessExclusiveLocks
when replayed on standby.
Prior to PG10, aborting subtransactions that held an
AccessExclusiveLock failed to release the lock until top level commit or
abort. 49bff5300d fixed that.
However, 49bff5300d also introduced a similar bug where subtransaction
commit would fail to release an AccessExclusiveLock, leaving the lock to
be removed sometimes early and sometimes late. This commit fixes
that bug also. Backpatch to PG10 needed.
Tested by observation. Note need for multi-node isolationtester to improve
test coverage for this and other HS cases.
Reported-by: Simon Riggs
Author: Simon Riggs
Also this commit unifies some duplicated code in makeBufFile() and
BufFileOpenShared() into new function makeBufFileCommon().
Author: Antonin Houska
Reviewed-By: Thomas Munro, Tatsuo Ishii
Discussion: https://postgr.es/m/16139.1529049566%40localhost
GetRunningTransactionData() suggested that subxids were not worth
optimizing away if overflowed, yet they have already been removed
for that case.
Changes to LogAccessExclusiveLock() API forgot to remove the
prior comment when it was copied to LockAcquire().
32ac7a118f tried to fix a Hot Standby issue
reported by Greg Stark, but in doing so caused
a different bug to appear, noted by Andres Freund.
Revoke the core changes from 32ac7a118f,
leaving in its place a minor change in code
ordering and comments to explain for the future.
GetRunningTransactionData() should ignore VACUUM procs because in some
cases they are assigned xids. This could lead to holding back xmin via
the route of passing the xid to standby and then having that hold back
xmin on master via feedback.
Backpatch to 9.1 needed, but will only do so on supported versions.
Backpatch once proven on the buildfarm.
Reported-by: Greg Stark
Author: Simon Riggs
Reviewed-by: Amit Kapila
Discussion: https://postgr.es/m/CANP8+jJBYt=4PpTfiPb0UrH1_iPhzsxKH5Op_Wec634F0ohnAw@mail.gmail.com
Commit c37b3d08c dropped its added GetDataDirectoryCreatePerm call into
the wrong place in pg_resetwal.c, namely after the chdir to DataDir.
That broke invocations using a relative path, as reported by Tushar Ahuja.
We could have left it where it was and changed the argument to be ".",
but that'd result in a rather confusing error message in event of a
failure, so re-ordering seems like a better solution.
Similarly reorder operations in pg_rewind.c. The issue there is that
it doesn't seem like a good idea to do any actual operations before the
not-root check (on Unix) or the restricted token acquisition (on Windows).
I don't know that this is an actual bug, but I'm definitely not convinced
that it isn't, either.
Assorted other code review for c37b3d08c and da9b580d8: fix some
misspelled or otherwise badly worded comments, put the #include for
<sys/stat.h> where it actually belongs, etc.
Discussion: https://postgr.es/m/aeb9c3a7-3c3f-a57f-1a18-c8d4fcdc2a1f@enterprisedb.com
The principle behind the locking was not very well thought-out, and not
documented. Add a section in the README to explain how it's supposed to
work, and change the code so that it actually works that way.
This fixes two bugs:
1. If fast update was turned on concurrently, subsequent inserts to the
pending list would not conflict with predicate locks that were acquired
earlier, on entry pages. The included 'predicate-gin-fastupdate' test
demonstrates that. To fix, make all scans acquire a predicate lock on
the metapage. That lock represents a scan of the pending list, whether
or not there is a pending list at the moment. Forget about the
optimization to skip locking/checking for locks, when fastupdate=off.
2. If a scan finds no match, it still needs to lock the entry page. The
point of predicate locks is to lock the gabs between values, whether
or not there is a match. The included 'predicate-gin-nomatch' test
tests that case.
In addition to those two bug fixes, this removes some unnecessary locking,
following the principle laid out in the README. Because all items in
a posting tree have the same key value, a lock on the posting tree root is
enough to cover all the items. (With a very large posting tree, it would
possibly be better to lock the posting tree leaf pages instead, so that a
"skip scan" with a query like "A & B", you could avoid unnecessary conflict
if a new tuple is inserted with A but !B. But let's keep this simple.)
Also, some spelling fixes.
Author: Heikki Linnakangas with some editorization by me
Review: Andrey Borodin, Alexander Korotkov
Discussion: https://www.postgresql.org/message-id/0b3ad2c2-2692-62a9-3a04-5724f2af9114@iki.fi
Failure to use DatumGetFoo/FooGetDatum macros correctly, or at all,
causes some warnings about sign conversion. This is just cosmetic
at the moment but in principle it's a type violation, so clean up
the instances I could find.
autoprewarm.c and sharedfileset.c contained code that unportably
assumed that pid_t is the same size as int. We've variously dealt
with this by casting pid_t to int or to unsigned long for printing
purposes; I went with the latter.
Fix uninitialized-variable warning in RestoreGUCState. This is
a live bug in some sense, but of no great significance given that
nobody is very likely to care what "line number" is associated with
a GUC that hasn't got a source file recorded.
There were three related issues:
* BufFileAppend() incorrectly reset the seek position on the 'source' file.
As a result, if you had called BufFileRead() on the file before calling
BufFileAppend(), it got confused, and subsequent calls would read/write
at wrong position.
* BufFileSize() did not work with files opened with BufFileOpenShared().
* FileGetSize() only worked on temporary files.
To fix, change the way BufFileSize() works so that it works on shared
files. Remove FileGetSize() altogether, as it's no longer needed. Remove
buffilesize from TapeShare struct, as the leader process can simply call
BufFileSize() to get the tape's size, there's no need to pass it through
shared memory anymore.
Discussion: https://www.postgresql.org/message-id/CAH2-WznEDYe_NZXxmnOfsoV54oFkTdMy7YLE2NPBLuttO96vTQ@mail.gmail.com
This change makes this module act more like most of our other low-level
resource management modules. It's a caller error if something is not
explicitly closed by the end of a successful transaction, so issue
a WARNING about it. This would not actually have caught the file leak
bug fixed in commit 231bcd080, because that was in a transaction-abort
path; but it still seems like a good, and pretty cheap, cross-check.
Discussion: https://postgr.es/m/152056616579.4966.583293218357089052@wrigleys.postgresql.org
One improbable error-exit path in this function used close() where
it should have used CloseTransientFile(). This is unlikely to be
hit in the field, and I think the consequences wouldn't be awful
(just an elog(LOG) bleat later). But a bug is a bug, so back-patch
to 9.4 where this code came in.
Pan Bian
Discussion: https://postgr.es/m/152056616579.4966.583293218357089052@wrigleys.postgresql.org
In commit 9c0a0de4c, I'd failed to notice that catalog/catalog.h
should also be considered a frontend-unsafe header, because it includes
(and needs) the full form of pg_class.h, not to mention relcache.h.
However, various frontend code was depending on it to get
TABLESPACE_VERSION_DIRECTORY, so refactoring of some sort is called for.
The cleanest answer seems to be to move TABLESPACE_VERSION_DIRECTORY,
as well as the OIDCHARS symbol, to common/relpath.h. Do that, and mop up
inclusions as necessary. (I found that quite a few current users of
catalog/catalog.h don't seem to need it at all anymore, apparently as a
result of the refactorings that created common/relpath.[hc]. And
initdb.c needed it only as a route to pg_class_d.h.)
Discussion: https://postgr.es/m/6629.1523294509@sss.pgh.pa.us
This reverts the backend sides of commit 1fde38beaa.
I have, at least for now, left the pg_verify_checksums tool in place, as
this tool can be very valuable without the rest of the patch as well,
and since it's a read-only tool that only runs when the cluster is down
it should be a lot safer.
Consolidate directory and file create permissions for tools which work
with the PG data directory by adding a new module (common/file_perm.c)
that contains variables (pg_file_create_mode, pg_dir_create_mode) and
constants to initialize them (0600 for files and 0700 for directories).
Convert mkdir() calls in the backend to MakePGDirectory() if the
original call used default permissions (always the case for regular PG
directories).
Add tests to make sure permissions in PGDATA are set correctly by the
tools which modify the PG data directory.
Authors: David Steele <david@pgmasters.net>,
Adam Brightwell <adam.brightwell@crunchydata.com>
Reviewed-By: Michael Paquier, with discussion amongst many others.
Discussion: https://postgr.es/m/ad346fe6-b23e-59f1-ecb7-0e08390ad629%40pgmasters.net
Hash index searches acquire predicate locks on the primary
page of a bucket. It acquires a lock on both the old and new buckets
for scans that happen concurrently with page splits. During a bucket
split, a predicate lock is copied from the primary page of an old
bucket to the primary page of a new bucket.
Author: Shubham Barai, Amit Kapila
Reviewed by: Amit Kapila, Alexander Korotkov, Thomas Munro
Discussion: https://www.postgresql.org/message-id/flat/CALxAEPvNsM2GTiXdRgaaZ1Pjd1bs+sxfFsf7Ytr+iq+5JJoYXA@mail.gmail.com
This makes it possible to turn checksums on in a live cluster, without
the previous need for dump/reload or logical replication (and to turn it
off).
Enabling checkusm starts a background process in the form of a
launcher/worker combination that goes through the entire database and
recalculates checksums on each and every page. Only when all pages have
been checksummed are they fully enabled in the cluster. Any failure of
the process will revert to checksums off and the process has to be
started.
This adds a new WAL record that indicates the state of checksums, so
the process works across replicated clusters.
Authors: Magnus Hagander and Daniel Gustafsson
Review: Tomas Vondra, Michael Banck, Heikki Linnakangas, Andrey Borodin
When SSI was developed, slru.c was limited to segment files with names in
the range 0000-FFFF. This didn't allow enough space for predicate.c to
store every possible XID when spilling old transactions to disk, so it
would wrap around sooner and print warnings. Since commits 638cf09e and
73c986ad increased the number of segment files slru.c could manage, that
behavior is unnecessary. Therefore remove that code.
Also remove the macro OldSerXidSegment, which has been unused since
4cd3fb6e.
Thomas Munro, reviewed by Anastasia Lubennikova
Discussion: https://postgr.es/m/CAEepm=3XfsTSxgEbEOmxu0QDiXy0o18NUg2nC89JZcCGE+XFPA@mail.gmail.com
Predicate locks are used on per page basis only if fastupdate = off, in
opposite case predicate lock on pending list will effectively lock whole index,
to reduce locking overhead, just lock a relation. Entry and posting trees are
essentially B-tree, so locks are acquired on leaf pages only.
Author: Shubham Barai with some editorization by me and Dmitry Ivanov
Review by: Alexander Korotkov, Dmitry Ivanov, Fedor Sigaev
Discussion: https://www.postgresql.org/message-id/flat/CALxAEPt5sWW+EwTaKUGFL5_XFcZ0MuGBcyJ70oqbWqr42YKR8Q@mail.gmail.com
Just noticed that these were quite redundant, since we're holding the
page address in a local variable anyway, and we have pin on the buffer
throughout.
Also improve a comment.
FreeSpaceMapVacuumRange has the same effect, is more efficient if many
pages are involved, and makes fewer assumptions about how it's used.
Notably, Claudio Freire pointed out that UpdateFreeSpaceMap could fail
if the specified freespace value isn't the maximum possible. This isn't
a problem for the single existing user, but the function represents an
attractive nuisance IMO, because it's named as though it were a
general-purpose update function and its limitations are undocumented.
In any case we don't need multiple ways to get the same result.
In passing, do some code review and cleanup in RelationAddExtraBlocks.
In particular, I see no excuse for it to omit the PageIsNew safety check
that's done in the mainline extension path in RelationGetBufferForTuple.
Discussion: https://postgr.es/m/CAGTBQpYR0uJCNTt3M5GOzBRHo+-GccNO1nCaQ8yEJmZKSW5q1A@mail.gmail.com
VACUUM updates leaf-level FSM entries immediately after cleaning the
corresponding heap blocks. fsmpage.c updates the intra-page search trees
on the leaf-level FSM pages when this happens, but it does not touch the
upper-level FSM pages, so that the released space might not actually be
findable by searchers. Previously, updating the upper-level pages happened
only at the conclusion of the VACUUM run, in a single FreeSpaceMapVacuum()
call. This is bad because the VACUUM might get canceled before ever
reaching that point, so that from the point of view of searchers no space
has been freed at all, leading to table bloat.
We can improve matters by updating the upper pages immediately after each
cycle of index-cleaning and heap-cleaning, processing just the FSM pages
corresponding to the range of heap blocks we have now fully cleaned.
This adds a small amount of extra work, since the FSM pages leading down
to each range boundary will be touched twice, but it's pretty negligible
compared to everything else going on in a large VACUUM.
If there are no indexes, VACUUM doesn't work in cycles but just cleans
each heap page on first visit. In that case we just arbitrarily update
upper FSM pages after each 8GB of heap. That maintains the goal of not
letting all this work slide until the very end, and it doesn't seem worth
expending extra complexity on a case that so seldom occurs in practice.
In either case, the FSM is fully up to date before any attempt is made
to truncate the relation, so that the most likely scenario for VACUUM
cancellation no longer results in out-of-date upper FSM pages. When
we do successfully truncate, adjusting the FSM to reflect that is now
fully handled within FreeSpaceMapTruncateRel.
Claudio Freire, reviewed by Masahiko Sawada and Jing Wang, some additional
tweaks by me
Discussion: https://postgr.es/m/CAGTBQpYR0uJCNTt3M5GOzBRHo+-GccNO1nCaQ8yEJmZKSW5q1A@mail.gmail.com
Add page-level predicate locking, due to gist's code organization, patch seems
close to trivial: add check before page changing, add predicate lock before page
scanning. Although choosing right place to check is not simple: it should not
be called during index build, it should support insertion of new downlink and so
on.
Author: Shubham Barai with editorization by me and Alexander Korotkov
Reviewed by: Alexander Korotkov, Andrey Borodin, me
Discussion: https://www.postgresql.org/message-id/flat/CALxAEPtdcANpw5ePU3LvnTP8HCENFw6wygupQAyNBgD-sG3h0g@mail.gmail.com
For years, our makefiles have correctly observed that "there is no correct
way to write a rule that generates two files". However, what we did is to
provide empty rules that "generate" the secondary output files from the
primary one, and that's not right either. Depending on the details of
the creating process, the primary file might end up timestamped later than
one or more secondary files, causing subsequent make runs to consider the
secondary file(s) out of date. That's harmless in a plain build, since
make will just re-execute the empty rule and nothing happens. But it's
fatal in a VPATH build, since make will expect the secondary file to be
rebuilt in the build directory. This would manifest as "file not found"
failures during VPATH builds from tarballs, if we were ever unlucky enough
to ship a tarball with apparently out-of-date secondary files. (It's not
clear whether that has ever actually happened, but it definitely could.)
To ensure that secondary output files have timestamps >= their primary's,
change our makefile convention to be that we provide a "touch $@" action
not an empty rule. Also, make sure that this rule actually gets invoked
during a distprep run, else the hazard remains.
It's been like this a long time, so back-patch to all supported branches.
In HEAD, I skipped the changes in src/backend/catalog/Makefile, because
those rules are due to get replaced soon in the bootstrap data format
patch, and there seems no need to create a merge issue for that patch.
If for some reason we fail to land that patch in v11, we'll need to
back-fill the changes in that one makefile from v10.
Discussion: https://postgr.es/m/18556.1521668179@sss.pgh.pa.us
Commit 34db06ef9a adopted a lock-free
design for shm_mq.c, but it introduced a race condition that could
lose messages. When shm_mq_receive_bytes() detects that the other end
has detached, it must make sure that it has seen the final version of
mq_bytes_written, or it might miss a message sent before detaching.
Thomas Munro
Discussion: https://postgr.es/m/CAEepm%3D2myZ4qxpt1a%3DC%2BwEv3o188K13K3UvD-44FK0SdAzHy%2Bw%40mail.gmail.com
Instead of marking data from the ringer buffer consumed and setting the
sender's latch for every message, do it only when the amount of data we
can consume is at least 1/4 of the size of the ring buffer, or when no
data remains in the ring buffer. This is dramatically faster in my
testing; apparently, the savings from sending signals less frequently
outweighs the benefit of letting the sender know about available buffer
space sooner.
Patch by me, reviewed by Andres Freund and tested by Rafia Sabih.
Discussion: http://postgr.es/m/CA+TgmoYK7RFj6r7KLEfSGtYZCi3zqTRhAz8mcsDbUAjEmLOZ3Q@mail.gmail.com
Previously, mq_bytes_read and mq_bytes_written were protected by the
spinlock, but that turns out to cause pretty serious spinlock
contention on queries which send many tuples through a Gather or
Gather Merge node. This patches changes things so that we instead
read and write those values using 8-byte atomics. Since mq_bytes_read
can only be changed by the receiver and mq_bytes_written can only be
changed by the sender, the only purpose of the spinlock is to prevent
reads and writes of these values from being torn on platforms where
8-byte memory access is not atomic, making the conversion fairly
straightforward.
Testing shows that this produces some slowdown if we're using emulated
64-bit atomics, but since they should be available on any platform
where performance is a primary concern, that seems OK. It's faster,
sometimes a lot faster, on platforms where such atomics are available.
Patch by me, reviewed by Andres Freund, who also suggested the
design. Also tested by Rafia Sabih.
Discussion: http://postgr.es/m/CA+TgmoYuK0XXxmUNTFT9TSNiBtWnRwasBcHHRCOK9iYmDLQVPg@mail.gmail.com
elog(FATAL) would end up calling PortalCleanup(), which would call
executor shutdown code, which could fail and crash, especially under
parallel query. This was introduced by
8561e4840c, which did not want to mark an
active portal as failed by a normal transaction abort anymore. But we
do need to do that for an elog(FATAL) exit. Introduce a variable
shmem_exit_inprogress similar to the existing proc_exit_inprogress, so
we can tell whether we are in the FATAL exit scenario.
Reported-by: Andres Freund <andres@anarazel.de>
Seems a bit silly that many (in fact all, as of today) uses of
StaticAssertExpr would need to cast it to void to avoid warnings from
pickier compilers. Let's just do the cast right in the macro, instead.
In passing, change StaticAssertExpr to StaticAssertStmt in one
place where that seems more apropos.
Discussion: https://postgr.es/m/16161.1518715186@sss.pgh.pa.us
To make this work, tuplesort.c and logtape.c must also support
parallelism, so this patch adds that infrastructure and then applies
it to the particular case of parallel btree index builds. Testing
to date shows that this can often be 2-3x faster than a serial
index build.
The model for deciding how many workers to use is fairly primitive
at present, but it's better than not having the feature. We can
refine it as we get more experience.
Peter Geoghegan with some help from Rushabh Lathia. While Heikki
Linnakangas is not an author of this patch, he wrote other patches
without which this feature would not have been possible, and
therefore the release notes should possibly credit him as an author
of this feature. Reviewed by Claudio Freire, Heikki Linnakangas,
Thomas Munro, Tels, Amit Kapila, me.
Discussion: http://postgr.es/m/CAM3SWZQKM=Pzc=CAHzRixKjp2eO5Q0Jg1SoFQqeXFQ647JiwqQ@mail.gmail.com
Discussion: http://postgr.es/m/CAH2-Wz=AxWqDoVvGU7dq856S4r6sJAj6DBn7VMtigkB33N5eyg@mail.gmail.com
It seems incorrect to assume that the list of CkptSortItems can never
contain duplicate page numbers: concurrent activity could result in some
page getting dropped from a low-numbered buffer and later loaded into a
high-numbered buffer while BufferSync is scanning the buffer pool.
If that happened, the comparator would give self-inconsistent results,
potentially confusing qsort(). Saving one comparison step is not worth
possibly getting the sort wrong.
So far as I can tell, nothing would actually go wrong given our current
implementation of qsort(). It might get a bit slower than expected
if there were a large number of duplicates of one value, but that's
surely a probability-epsilon case. Still, the comment is wrong,
and if we ever switched to another sort implementation it might be
less forgiving.
In passing, avoid casting away const-ness of the argument pointers;
I've not seen any compiler complaints from that, but it seems likely
that some compilers would not like it.
Back-patch to 9.6 where this code came in, just in case I've underestimated
the possible consequences.
Discussion: https://postgr.es/m/18437.1515607610@sss.pgh.pa.us
The general assumption for postmaster child processes is that they
should just exit(1), reasonably promptly, if the postmaster disappears.
condition_variable.c neglected this consideration and could be left
waiting forever, if the counterpart process it is waiting for has
done the right thing and exited.
We had some discussion of adjusting the WaitEventSet API to make it
harder to make this type of mistake in future; but for the moment,
and for v10, let's make this narrow fix.
Discussion: https://postgr.es/m/20412.1515456143@sss.pgh.pa.us
The original coding here insisted that callers manually cancel any prepared
sleep for one condition variable before starting a sleep on another one.
While that's not a huge burden today, it seems like a gotcha that will bite
us in future if the use of condition variables increases; anything we can
do to make the use of this API simpler and more robust is attractive.
Hence, allow these functions to automatically switch their attention to
a different CV when required. This is safe for the same reason it was OK
for commit aced5a92b to let a broadcast operation cancel any prepared CV
sleep: whenever we return to the other test-and-sleep loop, we will
automatically re-prepare that CV, paying at most an extra test of that
loop's exit condition.
Back-patch to v10 where condition variables were introduced. Ordinarily
we would probably not back-patch a change like this, but since it does not
invalidate any coding pattern that was legal before, it seems safe enough.
Furthermore, there's an open bug in replorigin_drop() for which the
simplest fix requires this. Even if we chose to fix that in some more
complicated way, the hazard would remain that we might back-patch some
other bug fix that requires this behavior.
Patch by me, reviewed by Thomas Munro.
Discussion: https://postgr.es/m/2437.1515368316@sss.pgh.pa.us
Previously, although the initial state of a proclist_node is expected
to be next == prev == 0, proclist_delete_offset would reset nodes to
next == prev == INVALID_PGPROCNO when removing them from a list.
This is the same state that a node in a singleton list has, so that
it's impossible to distinguish not-in-a-list from in-a-list. Change
proclist_delete_offset to reset removed nodes to next == prev == 0,
making it possible to distinguish those cases, and then add Asserts
to the list add and delete functions that the supplied node isn't
or is in a list at entry. Also tighten assertions about the node
being in the particular list (not some other one) where it is possible
to check that in O(1) time.
In ConditionVariablePrepareToSleep, since we don't expect the process's
cvWaitLink to already be in a list, remove the more-or-less-useless
proclist_contains check; we'd rather have proclist_push_tail's new
assertion fire if that happens.
Improve various comments related to proclists, too.
Patch by me, reviewed by Thomas Munro. This isn't back-patchable, since
there could theoretically be inlined copies of proclist_delete_offset in
third-party modules. But it's only improving debuggability anyway.
Discussion: https://postgr.es/m/CAEepm=0NWKehYw7NDoUSf8juuKOPRnCyY3vuaSvhrEWsOTAa3w@mail.gmail.com
In commit 561885db0, as part of normalizing RemovePgTempFiles's error
handling, I removed its behavior of silently ignoring ENOENT failures
during directory opens. Thomas Munro points out that this is a bad idea at
the top level, because we don't create pgsql_tmp directories until needed.
Thus this coding could produce LOG messages in perfectly normal situations,
which isn't what I intended. Restore the suppression of ENOENT logging,
but only at top level --- it would still be unexpected for a nested temp
directory to disappear between seeing it in the parent directory and
opening it.
Discussion: https://postgr.es/m/CAEepm=2y06SehAkTnd5sU_eVqdv5P-=Srt1y5vYNQk6yVDVaPw@mail.gmail.com
In the wake of commit aced5a92b, the semantics of these results are
a bit squishy: we can tell whether we signaled some other process(es),
but we do not know which ones were real waiters versus mere sentinels
for ConditionVariableBroadcast operations. It does not help much that
ConditionVariableBroadcast will attempt to pass on the signal to the
next real waiter, because (a) there might not be one, and (b) that will
only happen awhile later, anyway. So these results could overstate how
much effect the calls really had.
However, no existing caller of either function pays any attention to its
result value, so it seems reasonable to just define that as a required
property of a correct algorithm. To encourage correctness and save some
tiny number of cycles, change both functions to return void.
Patch by me, per an observation by Thomas Munro. No back-patch, since
if any third parties happen to be using these functions, they might not
appreciate an API break in a minor release.
Discussion: https://postgr.es/m/CAEepm=0NWKehYw7NDoUSf8juuKOPRnCyY3vuaSvhrEWsOTAa3w@mail.gmail.com
In the admittedly-very-unlikely case that AddWaitEventToSet fails,
ConditionVariablePrepareToSleep would error out after already having
set cv_sleep_target, which is probably bad, and after having already
set cv_wait_event_set, which is very bad. Transaction abort might or
might not clean up cv_sleep_target properly; but there is nothing
that would be aware that the WaitEventSet wasn't fully constructed,
so that all future condition variable sleeps would be broken.
We can easily guard against these hazards with slight restructuring.
Back-patch to v10 where condition_variable.c was introduced.
Discussion: https://postgr.es/m/CAEepm=0NWKehYw7NDoUSf8juuKOPRnCyY3vuaSvhrEWsOTAa3w@mail.gmail.com
The original implementation of ConditionVariableBroadcast was, per its
self-description, "the dumbest way possible". Thomas Munro found out
it was a bit too dumb. An awakened process may immediately re-queue
itself, if the specific condition it's waiting for is not yet satisfied.
If this happens before ConditionVariableBroadcast is able to see the wait
queue as empty, then ConditionVariableBroadcast will re-awaken the same
process, repeating the cycle. Given unlucky timing this back-and-forth
can repeat indefinitely; loops lasting thousands of seconds have been
seen in testing.
To fix, add our own process to the end of the wait queue to serve as a
sentinel, and exit the broadcast loop once our process is not there
anymore. There are various special considerations described in the
comments, the principal disadvantage being that wakers can no longer
be sure whether they awakened a real waiter or just a sentinel. But in
practice nobody pays attention to the result of ConditionVariableSignal
or ConditionVariableBroadcast anyway, so that problem seems hypothetical.
Back-patch to v10 where condition_variable.c was introduced.
Tom Lane and Thomas Munro
Discussion: https://postgr.es/m/CAEepm=0NWKehYw7NDoUSf8juuKOPRnCyY3vuaSvhrEWsOTAa3w@mail.gmail.com
XactLockTableWait assumed that its xid argument has already added itself
to the lock table. That assumption led to another assumption that if
locking the xid has succeeded but the xid is reported as still in
progress, then the input xid must have been a subtransaction.
These assumptions hold true for the original uses of this code in
locking related to on-disk tuples, but they break down in logical
replication slot snapshot building -- in particular, when a standby
snapshot logged contains an xid that's already in ProcArray but not yet
in the lock table. This leads to assertion failures that can be
reproduced all the way back to 9.4, when logical decoding was
introduced.
To fix, change SubTransGetParent to SubTransGetTopmostTransaction which
has a slightly different API: it returns the argument Xid if there is no
parent, and it goes all the way to the top instead of moving up the
levels one by one. Also, to avoid busy-waiting, add a 1ms sleep to give
the other process time to register itself in the lock table.
For consistency, change ConditionalXactLockTableWait the same way.
Author: Petr Jelínek
Discussion: https://postgr.es/m/1B3E32D8-FCF4-40B4-AEF9-5C0E3AC57969@postgrespro.ru
Reported-by: Konstantin Knizhnik
Diagnosed-by: Stas Kelvich, Petr Jelínek
Reviewed-by: Andres Freund, Robert Haas
SharedTuplestore allows multiple participants to write into it and
then read the tuples back from it in parallel. Each reader receives
partial results.
For now it always uses disk files, but other buffering policies and
other kinds of scans (ie each reader receives complete results) may be
useful in future.
The upcoming parallel hash join feature will use this facility.
Author: Thomas Munro
Reviewed-By: Peter Geoghegan, Andres Freund, Robert Haas
Discussion: https://postgr.es/m/CAEepm=2W=cOkiZxcg6qiFQP-dHUe09aqTrEMM7yJDrHMhDv_RA@mail.gmail.com
Crash restarts currently don't clean up temporary files, as a debugging aid.
If a left-over file happens to have the same name as a segment file we're
trying to create, we'll just truncate and reuse it, but there is a problem:
BufFileOpenShared() determines how many segment files exist by trying to open
.0, .1, .2, ... until it finds no more files. It might be confused by a junk
file that has the next segment number. To defend against that, make sure we
always create a gap after the end file by unlinking the following name if it
exists. Also make it an error to try to open a BufFile that doesn't exist
(has no segment 0), so as not to encourage the development of client code
that depends on an interface that we can't reliably provide.
Author: Thomas Munro
Reviewed-By: Andres Freund
Discussion: https://postgr.es/m/CAEepm%3D2jhCbC_GFQJaaDhWxLB4EXtT3vVd5czuRNaqF5CWSTog%40mail.gmail.com
When we create an Append node, we can spread out the workers over the
subplans instead of piling on to each subplan one at a time, which
should typically be a bit more efficient, both because the startup
cost of any plan executed entirely by one worker is paid only once and
also because of reduced contention. We can also construct Append
plans using a mix of partial and non-partial subplans, which may allow
for parallelism in places that otherwise couldn't support it.
Unfortunately, this patch doesn't handle the important case of
parallelizing UNION ALL by running each branch in a separate worker;
the executor infrastructure is added here, but more planner work is
needed.
Amit Khandekar, Robert Haas, Amul Sul, reviewed and tested by
Ashutosh Bapat, Amit Langote, Rafia Sabih, Amit Kapila, and
Rajkumar Raghuwanshi.
Discussion: http://postgr.es/m/CAJ3gD9dy0K_E8r727heqXoBmWZ83HwLFwdcaSSmBQ1+S+vRuUQ@mail.gmail.com
Previously, this code just reported such problems at LOG level and kept
going. The problem with this approach is that transient failures (e.g.,
ENFILE) could prevent us from resetting unlogged relations to empty,
yet allow recovery to appear to complete successfully. That seems like
a data corruption hazard large enough to treat such problems as reasons
to fail startup.
For the same reason, treat unlink failures for unlogged files as hard
errors not just LOG messages. It's a little odd that we did it like that
when file-level errors in other steps (copy_file, fsync_fname) are ERRORs.
The sole case that I left alone is that ENOENT failure on a tablespace
(not database) directory is not an error, though it will now be logged
rather than just silently ignored. This is to cover the scenario where
a previous DROP TABLESPACE removed the tablespace directory but failed
before removing the pg_tblspc symlink. I'm not sure that that's very
likely in practice, but that seems like the only real excuse for the
old behavior here, so let's allow for it. (As coded, this will also
allow ENOENT on $PGDATA/base/. But since we'll fail soon enough if
that's gone, I don't think we need to complicate this code by
distinguishing that from a true tablespace case.)
Discussion: https://postgr.es/m/21040.1512418508@sss.pgh.pa.us
Modify this function and its subsidiaries so that syscall failures are
reported via ereport(LOG), rather than silently ignored as before.
We don't want to throw a hard ERROR, as that would prevent database
startup, and getting rid of leftover temporary files is not important
enough for that. On the other hand, not reporting trouble at all
seems like an odd choice not in line with current project norms,
especially since any failure here is quite unexpected.
On the same reasoning, adjust these functions' AllocateDir/ReadDir calls
so that failure to scan a directory results in LOG not ERROR. I also
removed the previous practice of silently ignoring ENOENT failures during
directory opens --- there are some corner cases where that could happen
given a previous database crash, but that seems like a bad excuse for
ignoring a condition that isn't expected in most cases. A LOG message
during postmaster start seems OK in such situations, and better than
no output at all.
In passing, make RemovePgTempRelationFiles' test for "is the file name
all digits" look more like the way it's done elsewhere.
Discussion: https://postgr.es/m/19907.1512402254@sss.pgh.pa.us
This patch fixes a couple of low-probability bugs that could lead to
reporting an irrelevant errno value (and hence possibly a wrong SQLSTATE)
concerning directory-open or file-open failures. It also fixes places
where we took shortcuts in reporting such errors, either by using elog
instead of ereport or by using ereport but forgetting to specify an
errcode. And it eliminates a lot of just plain redundant error-handling
code.
In service of all this, export fd.c's formerly-static function
ReadDirExtended, so that external callers can make use of the coding
pattern
dir = AllocateDir(path);
while ((de = ReadDirExtended(dir, path, LOG)) != NULL)
if they'd like to treat directory-open failures as mere LOG conditions
rather than errors. Also fix FreeDir to be a no-op if we reach it
with dir == NULL, as such a coding pattern would cause.
Then, remove code at many call sites that was throwing an error or log
message for AllocateDir failure, as ReadDir or ReadDirExtended can handle
that job just fine. Aside from being a net code savings, this gets rid of
a lot of not-quite-up-to-snuff reports, as mentioned above. (In some
places these changes result in replacing a custom error message such as
"could not open tablespace directory" with more generic wording "could not
open directory", but it was agreed that the custom wording buys little as
long as we report the directory name.) In some other call sites where we
can't just remove code, change the error reports to be fully
project-style-compliant.
Also reorder code in restoreTwoPhaseData that was acquiring a lock
between AllocateDir and ReadDir; in the unlikely but surely not
impossible case that LWLockAcquire changes errno, AllocateDir failures
would be misreported. There is no great value in opening the directory
before acquiring TwoPhaseStateLock, so just do it in the other order.
Also fix CheckXLogRemoved to guarantee that it preserves errno,
as quite a number of call sites are implicitly assuming. (Again,
it's unlikely but I think not impossible that errno could change
during a SpinLockAcquire. If so, this function was broken for its
own purposes as well as breaking callers.)
And change a few places that were using not-per-project-style messages,
such as "could not read directory" when "could not open directory" is
more correct.
Back-patch the exporting of ReadDirExtended, in case we have occasion
to back-patch some fix that makes use of it; it's not needed right now
but surely making it global is pretty harmless. Also back-patch the
restoreTwoPhaseData and CheckXLogRemoved fixes. The rest of this is
essentially cosmetic and need not get back-patched.
Michael Paquier, with a bit of additional work by me
Discussion: https://postgr.es/m/CAB7nPqRpOCxjiirHmebEFhXVTK7V5Jvw4bz82p7Oimtsm3TyZA@mail.gmail.com
Provide support for dynamic or static parties of processes to wait for
all processes to reach point in the code before continuing.
This is similar to the mechanism of the same name in POSIX threads and
MPI, though has explicit phasing and dynamic party support like the
Java core library's Phaser.
This will be used by an upcoming patch adding support for parallel
hash joins.
Author: Thomas Munro
Reviewed-By: Andres Freund
Discussion: https://postgr.es/m/CAEepm=2_y7oi01OjA_wLvYcWMc9_d=LaoxrY3eiROCZkB_qakA@mail.gmail.com
Commit 11e264517 removed BufFile's isTemp flag, thereby eliminating
the possibility of resurrecting BufFileCreate(). But it left that
function in place, as well as a bunch of comments describing how things
worked for the non-temp-file case. At best, that's now a source of
confusion. So remove the long-since-commented-out function and change
relevant comments.
I (tgl) wanted to rename BufFileCreateTemp() to BufFileCreate(), but
that seems not to be the consensus position, so leave it as-is.
In passing, fix commit f0828b2fc's failure to update BufFileSeek's
comment to match the change of its argument type from long to off_t.
(I think that might actually have been intentional at the time, but
now that 64-bit off_t is nearly universal, it looks anachronistic.)
Thomas Munro and Tom Lane
Discussion: https://postgr.es/m/E1eFVyl-0008J1-RO@gemulon.postgresql.org
Up to now, ACL checks for large objects happened at the level of
the SQL-callable functions, which led to CVE-2017-7548 because of a
missing check. Push them down to be enforced in inv_api.c as much
as possible, in hopes of preventing future bugs. This does have the
effect of moving read and write permission errors to happen at lo_open
time not loread or lowrite time, but that seems acceptable.
Michael Paquier and Tom Lane
Discussion: https://postgr.es/m/CAB7nPqRHmNOYbETnc_2EjsuzSM00Z+BWKv9sy6tnvSd5gWT_JA@mail.gmail.com
The point of having separate ResourceOwnerEnlargeFoo and
ResourceOwnerRememberFoo functions is so that resource allocation
can happen in between. Doing it in some other order is just wrong.
OpenTemporaryFile() did open(), enlarge, remember, which would leak the
open file if the enlarge step ran out of memory. Because fd.c has its own
layer of resource-remembering, the consequences look like they'd be limited
to an intratransaction FD leak, but it's still not good.
IncrBufferRefCount() did enlarge, remember, incr-refcount, which would blow
up if the incr-refcount step ever failed. It was safe enough when written,
but since the introduction of PrivateRefCountHash, I think the assumption
that no error could happen there is pretty shaky.
The odds of real problems from either bug are probably small, but still,
back-patch to supported branches.
Thomas Munro and Tom Lane, per a comment from Andres Freund
The lower case spellings are C and C++ standard and are used in most
parts of the PostgreSQL sources. The upper case spellings are only used
in some files/modules. So standardize on the standard spellings.
The APIs for ICU, Perl, and Windows define their own TRUE and FALSE, so
those are left as is when using those APIs.
In code comments, we use the lower-case spelling for the C concepts and
keep the upper-case spelling for the SQL concepts.
Reviewed-by: Michael Paquier <michael.paquier@gmail.com>
There doesn't seem to be any good reason to do the filling of the
itemidbase[] array separately from the first traversal of the pointers.
It's certainly not a win if there are any line pointers with storage,
and even if there aren't, this change doesn't insert code into the part
of the first loop that will be traversed in that case. So let's just
merge the two loops.
Yura Sokolov, reviewed by Claudio Freire
Discussion: https://postgr.es/m/e49befcc6f1d7099834c6fdf5c675a60@postgrespro.ru
Thomas Munro
Magnus Hagander
Andres Freund
Michael Paquier
Tom Lane
Alexander Korotkov
Peter Eisentraut
Fujii Masao
Andrew Dunstan
Simon Riggs
Tatsuo Ishii
Teodor Sigaev
Heikki Linnakangas
Stephen Frost
Bruce Momjian
Robert Haas
Alvaro Herrera