An oversight in setting the boundaries of known commit timestamps during
startup caused old commit timestamps to become inaccessible after a
server restart.
Author and reporter: Julien Rouhaud
Review, test code: Craig Ringer
INSERT ... ON CONFLICT (specifically ExecCheckHeapTupleVisible) contains
another example of this unsafe coding practice. It is much harder to get
a failure out of it than the case fixed in commit 6292c2339, because in
most scenarios any hint bits that could be set would have already been set
earlier in the command. However, Konstantin Knizhnik reported a failure
with a custom transaction manager, and it's clearly possible to get a
failure via a race condition in async-commit mode.
For lack of a reproducible example, no regression test case in this
commit.
I did some testing with Asserts added to tqual.c's functions, and can say
that running "make check-world" exposed these two bugs and no others.
The Asserts are messy enough that I've not added them to the code for now.
Report: <57EE93C8.8080504@postgrespro.ru>
Related-Discussion: <CAO3NbwOycQjt2Oqy2VW-eLTq2M5uGMyHnGm=RNga4mjqcYD7gQ@mail.gmail.com>
A transaction that conflicts against itself, for example
INSERT INTO t(pk) VALUES (1),(1) ON CONFLICT DO NOTHING;
should behave the same regardless of isolation level. It certainly
shouldn't throw a serialization error, as retrying will not help.
We got this wrong due to the ON CONFLICT logic not considering the case,
as reported by Jason Dusek.
Core of this patch is by Peter Geoghegan (based on an earlier patch by
Thomas Munro), though I didn't take his proposed code refactoring for fear
that it might have unexpected side-effects. Test cases by Thomas Munro
and myself.
Report: <CAO3NbwOycQjt2Oqy2VW-eLTq2M5uGMyHnGm=RNga4mjqcYD7gQ@mail.gmail.com>
Related-Discussion: <57EE93C8.8080504@postgrespro.ru>
Despite the argumentation I wrote in commit 7a2fe85b0, it's unsafe to do
this, because in corner cases it's possible for HeapTupleSatisfiesSelf
to try to set hint bits on the target tuple; and at least since 8.2 we
have required the buffer content lock to be held while setting hint bits.
The added regression test exercises one such corner case. Unpatched, it
causes an assertion failure in assert-enabled builds, or otherwise would
cause a hint bit change in a buffer we don't hold lock on, which given
the right race condition could result in checksum failures or other data
consistency problems. The odds of a problem in the field are probably
pretty small, but nonetheless back-patch to all supported branches.
Report: <19391.1477244876@sss.pgh.pa.us>
Show how to get the system's huge page size, rather than misleadingly
referring to PAGE_SIZE (which is usually understood to be the regular
page size). Show how to confirm whether huge pages have been allocated.
Minor wordsmithing. Back-patch to 9.4 where this section appeared.
Replace "Full path to ..." with "Full path name of ...". At least one
user has misinterpreted the existing wording as meaning "Directory
containing ...".
With track_io_timing = on, EXPLAIN (ANALYZE, BUFFERS) will emit fields
named like "I/O Read Time". The slash makes that invalid as an XML
element name, so that adding FORMAT XML would produce invalid XML.
We already have code in there to translate spaces to dashes, so let's
generalize that to convert anything that isn't a valid XML name character,
viz letters, digits, hyphens, underscores, and periods. We could just
reject slashes, which would run a bit faster. But the fact that this went
unnoticed for so long doesn't give me a warm feeling that we'd notice the
next creative violation, so let's make it a permanent fix.
Reported by Markus Winand, though this isn't his initial patch proposal.
Back-patch to 9.2 where track_io_timing was added. The problem is only
latent in 9.1, so I don't feel a need to fix it there.
Discussion: <E0BF6A45-68E8-45E6-918F-741FB332C6BB@winand.at>
This absorbs a fix for a symlink-manipulation bug in zic that was
introduced in 2016g. It probably isn't interesting for our use-case,
but I'm not quite sure, so let's update while we're at it.
This is mostly to absorb some corner-case fixes in zic for year-2037
timestamps. The other changes that have been made are unlikely to affect
our usage, but nonetheless we may as well take 'em.
IANA got rid of the really silly "abbreviation" and replaced it with one
that's only moderately silly. But it's still pointless, so keep on not
showing it.
DST law changes in Turkey. Historical corrections for America/Los_Angeles,
Europe/Kirov, Europe/Moscow, Europe/Samara, and Europe/Ulyanovsk.
Rename Asia/Rangoon to Asia/Yangon, with a backward compatibility link.
The IANA crew continue their campaign to replace invented time zone
abbrevations with numeric GMT offsets. This update changes numerous zones
in Antarctica and the former Soviet Union, for instance Antarctica/Casey
now reports "+08" not "AWST" in the pg_timezone_names view. I kept these
abbreviations in the tznames/ data files, however, so that we will still
accept them for input. (We may want to start trimming those files someday,
but today is not that day.)
An exception is that since IANA no longer claims that "AMT" is in use
in Armenia for GMT+4, I replaced it in the Default file with GMT-4,
corresponding to Amazon Time which is in use in South America. It may be
that that meaning is also invented and IANA will drop it in a future
update; but for now, it seems silly to give pride of place to a meaning
not traceable to IANA over one that is.
When a relation is truncated, it is important that the FSM is truncated as
well. Otherwise, after recovery, the FSM can return a page that has been
truncated away, leading to errors like:
ERROR: could not read block 28991 in file "base/16390/572026": read only 0
of 8192 bytes
We were using MarkBufferDirtyHint() to dirty the buffer holding the last
remaining page of the FSM, but during recovery, that might in fact not
dirty the page, and the FSM update might be lost.
To fix, use the stronger MarkBufferDirty() function. MarkBufferDirty()
requires us to do WAL-logging ourselves, to protect from a torn page, if
checksumming is enabled.
Also fix an oversight in visibilitymap_truncate: it also needs to WAL-log
when checksumming is enabled.
Analysis by Pavan Deolasee.
Discussion: <CABOikdNr5vKucqyZH9s1Mh0XebLs_jRhKv6eJfNnD2wxTn=_9A@mail.gmail.com>
Backpatch to 9.3, where we got data checksums.
CommandId is declared as uint32, and values up to 4G are indeed legal.
cidout() handles them properly by treating the value as unsigned int.
But cidin() was just using atoi(), which has platform-dependent behavior
for values outside the range of signed int, as reported by Bart Lengkeek
in bug #14379. Use strtoul() instead, as xidin() does.
In passing, make some purely cosmetic changes to make xidin/xidout
look more like cidin/cidout; the former didn't have a monopoly on
best practice IMO.
Neither xidin nor cidin make any attempt to throw error for invalid input.
I didn't change that here, and am not sure it's worth worrying about
since neither is really a user-facing type. The point is just to ensure
that indubitably-valid inputs work as expected.
It's been like this for a long time, so back-patch to all supported
branches.
Report: <20161018152550.1413.6439@wrigleys.postgresql.org>
bitshiftright() and bitshiftleft() would recursively call each other
infinitely if the user passed INT_MIN for the shift amount, due to integer
overflow in negating the shift amount. To fix, clamp to -VARBITMAXLEN.
That doesn't change the results since any shift distance larger than the
input bit string's length produces an all-zeroes result.
Also fix some places that seemed inadequately paranoid about input typmods
exceeding VARBITMAXLEN. While a typmod accepted by anybit_typmodin() will
certainly be much less than that, at least some of these spots are
reachable with user-chosen integer values.
Andreas Seltenreich and Tom Lane
Discussion: <87d1j2zqtz.fsf@credativ.de>
pgstat_twophase_postcommit is supposed to duplicate the math in
AtEOXact_PgStat, but it had missed out the bit about clearing
t_delta_live_tuples/t_delta_dead_tuples for a TRUNCATE.
It's harder than you might think to replicate the issue here, because
those counters would only be nonzero when a previous transaction in
the same backend had added/deleted tuples in the truncated table,
and those counts hadn't been sent to the stats collector yet.
Evident oversight in commit d42358efb. I've not added a regression
test for this; we tried to add one in d42358efb, and had to revert it
because it was too timing-sensitive for the buildfarm.
Back-patch to 9.5 where d42358efb came in.
Stas Kelvich
Discussion: <EB57BF68-C06D-4737-BDDC-4BA778F4E62B@postgrespro.ru>
It's not good for an inherited child constraint to be marked connoinherit;
that would result in the constraint not propagating to grandchild tables,
if any are created later. The code mostly prevented this from happening
but there was one case that was missed.
This is somewhat related to commit e55a946a8, which also tightened checks
on constraint merging. Hence, back-patch to 9.2 like that one. This isn't
so much because there's a concrete feature-related reason to stop there,
as to avoid having more distinct behaviors than we have to in this area.
Amit Langote
Discussion: <b28ee774-7009-313d-dd55-5bdd81242c41@lab.ntt.co.jp>
Even if Linux's mmap() is okay with a partial-hugepage request, munmap()
is not, as reported by Chris Richards. Therefore it behooves us to try
a bit harder to find out the actual hugepage size, instead of assuming
that we can skate by with a guess.
For the moment, just look into /proc/meminfo to find out the default
hugepage size, and use that. Later, on kernels that support requests
for nondefault sizes, we might try to consider other alternatives.
But that smells more like a new feature than a bug fix, especially if
we want to provide any way for the DBA to control it, so leave it for
another day.
I set this up to allow easy addition of platform-specific code for
non-Linux platforms, if needed; but right now there are no reports
suggesting that we need to work harder on other platforms.
Back-patch to 9.4 where hugepage support was introduced.
Discussion: <31056.1476303954@sss.pgh.pa.us>
Fix detaching of the mmap'd segment to have its own on_shmem_exit callback,
rather than piggybacking on the one for detaching from the SysV segment.
That was confusing, and given the distance between the two attach calls,
it was trouble waiting to happen.
Make the detaching calls idempotent by clearing AnonymousShmem to show
we've already unmapped. I spent quite a bit of time yesterday trying
to find a path that would allow the munmap()'s to be done twice, and
while I did not succeed, it seems silly that there's even a question.
Make the #ifdef logic less confusing by separating "do we want to use
anonymous shmem" from EXEC_BACKEND. Even though there's no current
scenario where those conditions are different, it is not helpful for
different places in the same file to be testing EXEC_BACKEND for what
are fundamentally different reasons.
Don't do on_exit_reset() in StartBackgroundWorker(). At best that's
useless (InitPostmasterChild would have done it already) and at worst
it could zap some callback that's unrelated to shared memory.
Improve comments, and simplify the huge_pages enablement logic slightly.
Back-patch to 9.4 where hugepage support was introduced.
Arguably this should go into 9.3 as well, but the code looks
significantly different there, and I doubt it's worth the
trouble of adapting the patch given I can't show a live bug.
This turns out not to be as harmless as I thought: MSVC will complain
if it sees an "extern" declaration without PGDLLEXPORT and then one with.
(Seems fairly silly, given that this can be changed after the fact by the
linker, but there you have it.) Therefore, contrib modules that have
extern's for V1 functions in header files are falling over in the
buildfarm, since none of those externs are marked PGDLLEXPORT.
We might or might not conclude that we're willing to plaster those
declarations with PGDLLEXPORT in HEAD, but in any case there's no way we're
going to ship this change in the back branches. Third-party authors would
not thank us for breaking their code in a minor release. Hence, revert
the addition of PGDLLEXPORT (but let's keep the extra info in the comment).
If we do the other changes we can revert this commit in HEAD.
Per buildfarm.
This isn't really necessary for our own code, because we use a .DEF file
in MSVC builds (see gendef.pl), or --export-all-symbols in MinGW and
Cygwin builds, to ensure that all global symbols in loadable modules
will be exported on Windows. However, third-party authors might use
different build processes that need this marker, and it's harmless
enough for our own builds.
To some extent, this is an oversight in commit e7128e8db, so back-patch
to 9.4 where that was added.
Laurenz Albe
Discussion: <A737B7A37273E048B164557ADEF4A58B539300BD@ntex2010a.host.magwien.gv.at>
It was perhaps not entirely clear that internal self-references shouldn't
be schema-qualified even if the view name is written with a schema.
Spell it out.
Discussion: <871sznz69m.fsf@metapensiero.it>
Ordinarily there would not be an async result sitting around at this
point, but it appears that in corner cases there can be. Considering
all the work we're about to launch, it's hardly going to cost anything
noticeable to check.
It's been like this forever, so back-patch to all supported branches.
Report: <CAD-Qf1eLUtBOTPXyFQGW-4eEsop31tVVdZPu4kL9pbQ6tJPO8g@mail.gmail.com>
Historically, we've allowed users to add a CHECK constraint to a child
table and then add an identical CHECK constraint to the parent. This
results in "merging" the two constraints so that the pre-existing
child constraint ends up with both conislocal = true and coninhcount > 0.
However, if you tried to do it in the other order, you got a duplicate
constraint error. This is problematic for pg_dump, which needs to issue
separated ADD CONSTRAINT commands in some cases, but has no good way to
ensure that the constraints will be added in the required order.
And it's more than a bit arbitrary, too. The goal of complaining about
duplicated ADD CONSTRAINT commands can be served if we reject the case of
adding a constraint when the existing one already has conislocal = true;
but if it has conislocal = false, let's just make the ADD CONSTRAINT set
conislocal = true. In this way, either order of adding the constraints
has the same end result.
Another problem was that the code allowed creation of a parent constraint
marked convalidated that is merged with a child constraint that is
!convalidated. In this case, an inheritance scan of the parent table could
emit some rows violating the constraint condition, which would be an
unexpected result given the marking of the parent constraint as validated.
Hence, forbid merging of constraints in this case. (Note: valid child and
not-valid parent seems fine, so continue to allow that.)
Per report from Benedikt Grundmann. Back-patch to 9.2 where we introduced
possibly-not-valid check constraints. The second bug obviously doesn't
apply before that, and I think the first doesn't either, because pg_dump
only gets into this situation when dealing with not-valid constraints.
Report: <CADbMkNPT-Jz5PRSQ4RbUASYAjocV_KHUWapR%2Bg8fNvhUAyRpxA%40mail.gmail.com>
Discussion: <22108.1475874586@sss.pgh.pa.us>
Back-patch commit 0dba54f166 into the older
branches. This test is almost as much of a patching hazard there as it is
in HEAD, and it has no more reason to be needed than it does in HEAD.
I went back as far as 9.2; I judged 9.1 not worth the trouble since
it's on the verge of being EOL'd.
The need for this was previously obscured even on picky platforms
by the hack we used to support direct cross-module references in
the transforms contrib modules. Now that that hack is gone, the
undefined symbol is exposed, as reported by Robert Haas.
Back-patch to 9.5 where we started to use -Wl,-undefined,dynamic_lookup.
I'm a bit surprised that the older branches don't seem to contain
any gettext references in this module, but since they don't fail
at build time, they must not. (We might be able to get away with
leaving this alone in 9.5/9.6, but I think it's cleaner if the
reference gets resolved at link time.)
Report: <CA+TgmoaHJKU5kcWZcYduATYVT7Mnx+8jUnycaYYL7OtCwCigug@mail.gmail.com>
I somehow had assumed that in the spinlock (in turn possibly using
semaphores) based fallback atomics implementation 32 bit writes could be
done without a lock. As far as the write goes that's correct, since
postgres supports only platforms with single-copy atomicity for aligned
32bit writes. But writing without holding the spinlock breaks
read-modify-write operations like pg_atomic_compare_exchange_u32(),
since they'll potentially "miss" a concurrent write, which can't happen
in actual hardware implementations.
In 9.6+ when using the fallback atomics implementation this could lead
to buffer header locks not being properly marked as released, and
potentially some related state corruption. I don't see a related danger
in 9.5 (earliest release with the API), because pg_atomic_write_u32()
wasn't used in a concurrent manner there.
The state variable of local buffers, before this change, were
manipulated using pg_atomic_write_u32(), to avoid unnecessary
synchronization overhead. As that'd not be the case anymore, introduce
and use pg_atomic_unlocked_write_u32(), which does not correctly
interact with RMW operations.
This bug only caused issues when postgres is compiled on platforms
without atomics support (i.e. no common new platform), or when compiled
with --disable-atomics, which explains why this wasn't noticed in
testing.
Reported-By: Tom Lane
Discussion: <14947.1475690465@sss.pgh.pa.us>
Backpatch: 9.5-, where the atomic operations API was introduced.
Recent Perl and/or new Linux distributions are starting to remove "." from
the @INC list by default. That breaks pg_rewind and ssl test suites, which
use helper perl modules that reside in the same directory. To fix, add the
current source directory explicitly to prove's include dir.
The vcregress.pl script probably also needs something like this, but I
wasn't able to remove '.' from @INC on Windows to test this, and don't want
to try doing that blindly.
Discussion: <20160908204529.flg6nivjuwp5vaoy@alap3.anarazel.de>
They are supposed to be mutually exclusive, but there was no check for
that.
Michael Banck
Discussion: <20161007103414.GD12247@nighthawk.caipicrew.dd-dns.de>
Leaving the error in the error queue used to be harmless, because the
X509_STORE_load_locations() call used to be the last step in
initialize_SSL(), and we would clear the queue before the next
SSL_connect() call. But previous commit moved things around. The symptom
was that if a CRL file was not found, and one of the subsequent
initialization steps, like loading the client certificate or private key,
failed, we would incorrectly print the "no such file" error message from
the earlier X509_STORE_load_locations() call as the reason.
Backpatch to all supported versions, like the previous patch.
There were several issues with the old coding:
1. There was a race condition, if two threads opened a connection at the
same time. We used a mutex around SSL_CTX_* calls, but that was not
enough, e.g. if one thread SSL_CTX_load_verify_locations() with one
path, and another thread set it with a different path, before the first
thread got to establish the connection.
2. Opening two different connections, with different sslrootcert settings,
seemed to fail outright with "SSL error: block type is not 01". Not sure
why.
3. We created the SSL object, before calling SSL_CTX_load_verify_locations
and SSL_CTX_use_certificate_chain_file on the SSL context. That was
wrong, because the options set on the SSL context are propagated to the
SSL object, when the SSL object is created. If they are set after the
SSL object has already been created, they won't take effect until the
next connection. (This is bug #14329)
At least some of these could've been fixed while still using a shared
context, but it would've been more complicated and error-prone. To keep
things simple, let's just use a separate SSL context for each connection,
and accept the overhead.
Backpatch to all supported versions.
Report, analysis and test case by Kacper Zuk.
Discussion: <20160920101051.1355.79453@wrigleys.postgresql.org>
If you point pg_rewind to a server that is using synchronous replication,
with "pg_rewind --source-server=...", and the replication is not working
for some reason, pg_rewind will get stuck because it creates a temporary
table, which needs to be replicated. You could call broken replication a
pilot error, but pg_rewind is often used in special circumstances, when
there are changes to the replication setup.
We don't do any "real" updates, and we don't care about fsyncing or
replicating the operations on the temporary tables, so fix that by
setting synchronous_commit off.
Michael Banck, Michael Paquier. Backpatch to 9.5, where pg_rewind was
introduced.
Discussion: <20161005143938.GA12247@nighthawk.caipicrew.dd-dns.de>
Before initializing iteration over a subtransaction's changes, the last
few changes were not spilled to disk. That's correct if the transaction
didn't spill to disk, but otherwise... This bug can lead to missed or
misorderd subtransaction contents when they were spilled to disk.
Move spilling of the remaining in-memory changes to
ReorderBufferIterTXNInit(), where it can easily be applied to the top
transaction and, if present, subtransactions.
Since this code had too many bugs already, noticeably increase test
coverage.
Fixes: #14319
Reported-By: Huan Ruan
Discussion: <20160909012610.20024.58169@wrigleys.postgresql.org>
Backport: 9,4-, where logical decoding was added
Commit 88e982302 invented GUC_UNIT_XSEGS for min_wal_size and max_wal_size,
but neglected to make it display sensibly in pg_settings.unit (by adding a
case to the switch in GetConfigOptionByNum). Fix that, and adjust said
switch to throw a run-time error the next time somebody forgets.
In passing, avoid using a static buffer for the output string --- the rest
of this function pstrdup's from a local buffer, and I see no very good
reason why the units code should do it differently and less safely.
Per report from Otar Shavadze. Back-patch to 9.5 where the new unit type
was added.
Report: <CAG-jOyA=iNFhN+yB4vfvqh688B7Tr5SArbYcFUAjZi=0Exp-Lg@mail.gmail.com>
Attempting to COPY a subset of columns from a table with RLS enabled
would fail due to an invalid query being constructed (using a single
ColumnRef with the list of fields to exact in 'fields', but that's for
the different levels of an indirection for a single column, not for
specifying multiple columns).
Correct by building a ColumnRef and then RestTarget for each column
being requested and then adding those to the targetList for the select
query. Include regression tests to hopefully catch if this is broken
again in the future.
Patch-By: Adam Brightwell
Reviewed-By: Michael Paquier
pg_upgrade checks whether all the shared libraries used in the old cluster
are also available in the new one by issuing LOAD for each library name.
Previously, it cared not what order it did the LOADs in. Ideally it
should not have to care, but currently the transform modules in contrib
fail unless both the language and datatype modules they depend on are
loaded first. A backend-side solution for that looks possible but
probably not back-patchable, so as a stopgap measure, let's do the LOAD
tests in order by library name length. That should fix the problem for
reasonably-named transform modules, eg "hstore_plpython" will be loaded
after both "hstore" and "plpython". (Yeah, it's a hack.)
In a larger sense, having a predictable order of these probes is a good
thing, since it will make upgrades predictably work or not work in the
face of inter-library dependencies. Also, this patch replaces O(N^2)
de-duplication logic with O(N log N) logic, which could matter in
installations with very many databases. So I don't foresee reverting this
even after we have a proper fix for the library-dependency problem.
In passing, improve a couple of SQL queries used here.
Per complaint from Andrew Dunstan that pg_upgrade'ing the transform contrib
modules failed. Back-patch to 9.5 where transform modules were introduced.
Discussion: <f7ac29f3-515c-2a44-21c5-ec925053265f@dunslane.net>
In standard Unix builds, postmaster child processes do ClosePostmasterPorts
immediately after InitPostmasterChild, that is almost immediately after
being spawned. This is important because we don't want children holding
open the postmaster's end of the postmaster death watch pipe.
However, in EXEC_BACKEND builds, SubPostmasterMain was postponing this
responsibility significantly, in order to make it slightly more convenient
to pass the right flag value to ClosePostmasterPorts. This is bad,
particularly seeing that process_shared_preload_libraries() might invoke
nearly-arbitrary code. Rearrange so that we do it as soon as we've
fetched the socket FDs via read_backend_variables().
Also move the comment explaining about randomize_va_space to before the
call of PGSharedMemoryReAttach, which is where it's relevant. The old
placement was appropriate when the reattach happened inside
CreateSharedMemoryAndSemaphores, but that was a long time ago.
Back-patch to 9.3; the patch doesn't apply cleanly before that, and
it doesn't seem worth a lot of effort given that we've had no actual
field complaints traceable to this.
Discussion: <4157.1475178360@sss.pgh.pa.us>
There is a small window between when the server closes out the existing
segment and the new one is created. Put a loop around the open call in
this case to make sure we wait for the new file to actually appear.
<sys/select.h> is required by POSIX.1-2001 to get the prototype of
select(2), but nearly no systems enforce that because older standards
let you get away with including some other headers. Recent OpenBSD
hacking has removed that frail touch of friendliness, however, which
broke some compiles; fix all the way back to 9.1 by adding the required
standard. Only vacuumdb.c was reported to fail, but it seems easier to
fix the whole lot in a fell swoop.
Per bug #14334 by Sean Farrell.
Evidently an oversight in commit 729205571. Back-patch to 9.2 where
privileges for types were introduced.
Report: <20160922173517.8214.88959@wrigleys.postgresql.org>
When configured with --enable-tap-tests, "make install" will now install
the Perl support files for TAP testing where PGXS will find them.
This allows extensions to rely on $(prove_check) even when being built
out-of-tree. Back-patch to 9.4 where we first started to support TAP
testing, to reduce the number of cases extension makefiles need to
consider.
Craig Ringer
Discussion: <CAMsr+YFXv+2qne6xJW7z_25mYBtktRX5rpkrgrb+DRgQ_FxgHQ@mail.gmail.com>
These worked as-is until around 7.0, but fail in newer versions because
there are more operators named "#". Besides it's a bit inconsistent that
only two of the examples on this page lack type names on their constants.
Report: <20160923081530.1517.75670@wrigleys.postgresql.org>
Faulty AND/OR nesting in the WHERE clause of getFuncs' SQL query led to
dumping range constructor functions if they are part of an extension
and we're in binary-upgrade mode. Actually, we don't want to dump them
separately even then, since CREATE TYPE AS RANGE will create the range's
constructor functions regardless. Per report from Andrew Dunstan.
It looks like this mistake was introduced by me, in commit b985d4877, in
perhaps-overzealous refactoring to reduce code duplication. I'm suitably
embarrassed.
Report: <34854939-02d7-f591-5677-ce2994104599@dunslane.net>
We must test GetLastError() even when CreateFileMapping() returns a
non-null handle. If that value were left over from some previous system
call, we might be fooled into thinking the segment already existed.
Experimentation on Windows 7 suggests that CreateFileMapping() clears
the error code on success, but it is not documented to do so, so let's
not rely on that happening in all Windows releases.
Amit Kapila
Discussion: <20811.1474390987@sss.pgh.pa.us>
Alvaro Herrera
Tom Lane
Heikki Linnakangas
Andres Freund
Stephen Frost
Magnus Hagander
Robert Haas