37965 Commits

Author SHA1 Message Date
Tom Lane
0d01c5b932 Fix postmaster's handling of a startup-process crash.
Ordinarily, a failure (unexpected exit status) of the startup subprocess
should be considered fatal, so the postmaster should just close up shop
and quit.  However, if we sent the startup process a SIGQUIT or SIGKILL
signal, the failure is hardly "unexpected", and we should attempt restart;
this is necessary for recovery from ordinary backend crashes in hot-standby
scenarios.  I attempted to implement the latter rule with a two-line patch
in commit 442231d7f71764b8c628044e7ce2225f9aa43b67, but it now emerges that
that patch was a few bricks shy of a load: it failed to distinguish the
case of a signaled startup process from the case where the new startup
process crashes before reaching database consistency.  That resulted in
infinitely respawning a new startup process only to have it crash again.

To handle this properly, we really must track whether we have sent the
*current* startup process a kill signal.  Rather than add yet another
ad-hoc boolean to the postmaster's state, I chose to unify this with the
existing RecoveryError flag into an enum tracking the startup process's
state.  That seems more consistent with the postmaster's general state
machine design.

Back-patch to 9.0, like the previous patch.
2015-07-09 13:22:23 -04:00
Heikki Linnakangas
cf0c44611c Fix another broken link in documentation.
Tom fixed another one of these in commit 7f32dbcd, but there was another
almost identical one in libpq docs. Per his comment:

HP's web server has apparently become case-sensitive sometime recently.
Per bug #13479 from Daniel Abraham.  Corrected link identified by Alvaro.
2015-07-09 16:12:38 +03:00
Noah Misch
42b6922f31 Replace use of "diff -q".
POSIX does not specify the -q option, and many implementations do not
offer it.  Don't bother changing the MSVC build system, because having
non-GNU diff on Windows is vanishingly unlikely.  Back-patch to 9.2,
where this invocation was introduced.
2015-07-08 20:44:26 -04:00
Noah Misch
eb1525e896 Fix null pointer dereference in "\c" psql command.
The psql crash happened when no current connection existed.  (The second
new check is optional given today's undocumented NULL argument handling
in PQhost() etc.)  Back-patch to 9.0 (all supported versions).
2015-07-08 20:44:26 -04:00
Tom Lane
58c58d1a9f Fix portability issue in pg_upgrade test script: avoid $PWD.
SUSv2-era shells don't set the PWD variable, though anything more modern
does.  In the buildfarm environment this could lead to test.sh executing
with PWD pointing to $HOME or another high-level directory, so that there
were conflicts between concurrent executions of the test in different
branch subdirectories.  This appears to be the explanation for recent
intermittent failures on buildfarm members binturong and dingo (and might
well have something to do with the buildfarm script's failure to capture
log files from pg_upgrade tests, too).

To fix, just use `pwd` in place of $PWD.  AFAICS test.sh is the only place
in our source tree that depended on $PWD.  Back-patch to all versions
containing this script.

Per buildfarm.  Thanks to Oskari Saarenmaa for diagnosing the problem.
2015-07-07 12:49:18 -04:00
Heikki Linnakangas
992c6f0d2c Improve handling of out-of-memory in libpq.
If an allocation fails in the main message handling loop, pqParseInput3
or pqParseInput2, it should not be treated as "not enough data available
yet". Otherwise libpq will wait indefinitely for more data to arrive from
the server, and gets stuck forever.

This isn't a complete fix - getParamDescriptions and getCopyStart still
have the same issue, but it's a step in the right direction.

Michael Paquier and me. Backpatch to all supported versions.
2015-07-07 18:45:17 +03:00
Heikki Linnakangas
4dac5651b1 Turn install.bat into a pure one line wrapper fort he perl script.
Build.bat and vcregress.bat got similar treatment years ago. I'm not sure
why install.bat wasn't treated at the same time, but it seems like a good
idea anyway.

The immediate problem with the old install.bat was that it had quoting
issues, and wouldn't work if the target directory's name contained spaces.
This fixes that problem.

I committed this to master yesterday, this is a backpatch of the same for
all supported versions.
2015-07-07 16:31:52 +03:00
Andres Freund
81fc89a5eb Fix logical decoding bug leading to inefficient reopening of files.
When spilling transaction data to disk a simple typo caused the output
file to be closed and reopened for every serialized change. That happens
to not have a huge impact on linux, which is why it probably wasn't
noticed so far, but on windows that appears to trigger actual disk
writes after every change. Not fun.

The bug fortunately does not have any impact besides speed. A change
could end up being in the wrong segment (last instead of next), but
since we read all files to the end, that's just ugly, not really
problematic. It's not a problem to upgrade, since transaction spill
files do not persist across restarts.

Bug: #13484
Reported-By: Olivier Gosseaume
Discussion: 20150703090217.1190.63940@wrigleys.postgresql.org

Backpatch to 9.4, where logical decoding was added.
2015-07-07 13:12:59 +02:00
Andres Freund
1790b35baf Fix pg_recvlogical not to fsync output when it's a tty or pipe.
The previous coding tried to handle possible failures when fsyncing a
tty or pipe fd by accepting EINVAL - but apparently some
platforms (windows, OSX) don't reliably return that. So instead check
whether the output fd refers to a pipe or a tty when opening it.

Reported-By: Olivier Gosseaume, Marko Tiikkaja
Discussion: 559AF98B.3050901@joh.to

Backpatch to 9.4, where pg_recvlogical was added.
2015-07-07 13:07:50 +02:00
Fujii Masao
0471894a6f Remove incorrect warning from pg_archivecleanup document.
The .backup file name can be passed to pg_archivecleanup even if
it includes the extension which is specified in -x option.
However, previously the document incorrectly warned a user
not to do that.

Back-patch to 9.2 where pg_archivecleanup's -x option and
the warning were added.
2015-07-06 20:59:59 +09:00
Tom Lane
353f4fde79 Fix some typos in regression test comments.
Back-patch to avoid unnecessary cross-branch differences.

CharSyam
2015-07-05 13:14:50 -04:00
Tom Lane
60c38e62cd Make numeric form of PG version number readily available in Makefiles.
Expose PG_VERSION_NUM (e.g., "90600") as a Make variable; but for
consistency with the other Make variables holding similar info,
call the variable just VERSION_NUM not PG_VERSION_NUM.

There was some discussion of making this value available as a pg_config
value as well.  However, that would entail substantially more work than
this two-line patch.  Given that there was not exactly universal consensus
that we need this at all, let's just do a minimal amount of work for now.

Back-patch of commit a5d489ccb7e613c7ca3be6141092b8c1d2c13fa7, so that this
variable is actually useful for its intended purpose sometime before 2020.

Michael Paquier, reviewed by Pavel Stehule
2015-07-05 12:01:01 -04:00
Peter Eisentraut
4a1944ec6c PL/Perl: Add alternative expected file for Perl 5.22 2015-07-03 14:08:11 -04:00
Heikki Linnakangas
9d6352aaae Fix pgbench progress report behaviour when pgbench or a query gets stuck.
There were two issues here. First, if a query got stuck so that it took
e.g. 5 seconds, and progress interval was 1 second, no progress reports were
printed until the query returned. Fix so that we wake up specifically to
print the progress report. Secondly, if pgbench got stuck so that it would
nevertheless not print a progress report on time, and enough time passes
that it's already time to print the next progress report, just skip the one
that was missed. Before this patch, it would print the missed one with 0 TPS
immediately after the previous one.

Fabien Coelho. Backpatch to 9.4, where progress reports were added.
2015-07-03 11:15:27 +03:00
Heikki Linnakangas
0eaa49a5c4 Don't emit a spurious space at end of line in pg_dump of event triggers.
Backpatch to 9.3 and above, where event triggers were added.
2015-07-02 12:51:04 +03:00
Tom Lane
505f78c446 Fix broken link in documentation.
HP's web server has apparently become case-sensitive sometime recently.
Per bug #13479 from Daniel Abraham.  Corrected link identified by Alvaro.
2015-06-30 18:47:47 -04:00
Alvaro Herrera
ef704ec069 Test -lrt for sched_yield
Apparently, this is needed in some Solaris versions.

Author: Oskari Saarenmaa
2015-06-30 14:20:38 -03:00
Heikki Linnakangas
7dc721889b Don't call PageGetSpecialPointer() on page until it's been initialized.
After calling XLogInitBufferForRedo(), the page might be all-zeros if it was
not in page cache already. btree_xlog_unlink_page initialized the page
correctly, but it called PageGetSpecialPointer before initializing it, which
would lead to a corrupt page at WAL replay, if the unlinked page is not in
page cache.

Backpatch to 9.4, the bug came with the rewrite of B-tree page deletion.
2015-06-30 13:45:00 +03:00
Tom Lane
1afc1fe9c7 Back-patch some minor bug fixes in GUC code.
In 9.4, fix a 9.4.1 regression that allowed multiple entries for a
PGC_POSTMASTER variable to cause bogus complaints in the postmaster log.
(The issue here was that commit bf007a27acd7b2fb unintentionally reverted
3e3f65973a3c94a6, which suppressed any duplicate entries within
ParseConfigFp.  Back-patch the reimplementation just made in HEAD, which
makes use of an "ignore" field to prevent application of superseded items.)

Add missed failure check in AlterSystemSetConfigFile().  We don't really
expect ParseConfigFp() to fail, but that's not an excuse for not checking.

In both 9.3 and 9.4, remove mistaken assignment to ConfigFileLineno that
caused line counting after an include_dir directive to be completely wrong.
2015-06-28 18:38:06 -04:00
Kevin Grittner
f9f7150376 Fix comment for GetCurrentIntegerTimestamp().
The unit of measure is microseconds, not milliseconds.

Backpatch to 9.3 where the function and its comment were added.
2015-06-28 12:45:41 -05:00
Tatsuo Ishii
9a43799440 Fix function declaration style to respect the coding standard. 2015-06-28 19:04:39 +09:00
Andres Freund
ed6c8d7361 Fix test_decoding's handling of nonexistant columns in old tuple versions.
test_decoding used fastgetattr() to extract column values. That's wrong
when decoding updates and deletes if a table's replica identity is set
to FULL and new columns have been added since the old version of the
tuple was created. Due to the lack of a crosscheck with the datum's
natts values an invalid value will be output, leading to errors or
worse.

Bug: #13470
Reported-By: Krzysztof Kotlarski
Discussion: 20150626100333.3874.90852@wrigleys.postgresql.org

Backpatch to 9.4, where the feature, including the bug, was added.
2015-06-27 19:01:00 +02:00
Kevin Grittner
524e1e4031 Add opaque declaration of HTAB to tqual.h.
Commit b89e151054a05f0f6d356ca52e3b725dd0505e53 added the
ResolveCminCmaxDuringDecoding declaration to tqual.h, which uses an
HTAB parameter, without declaring HTAB.  It accidentally fails to
fail to build with current sources because a declaration happens to
be included, directly or indirectly, in all source files that
currently use tqual.h before tqual.h is first included, but we
shouldn't count on that.  Since an opaque declaration is enough
here, just use that, as was done in snapmgr.h.

Backpatch to 9.4, where the HTAB reference was added to tqual.h.
2015-06-27 09:55:08 -05:00
Simon Riggs
8ab0ef89d9 Revoke incorrectly applied patch version 2015-06-27 02:21:03 +01:00
Simon Riggs
9af67b667c Avoid hot standby cancels from VAC FREEZE
VACUUM FREEZE generated false cancelations of standby queries on an
otherwise idle master. Caused by an off-by-one error on cutoff_xid
which goes back to original commit.

Backpatch to all versions 9.0+

Analysis and report by Marco Nenciarini

Bug fix by Simon Riggs
2015-06-27 00:44:56 +01:00
Heikki Linnakangas
b6c4b58ac5 Fix a couple of bugs with wal_log_hints.
1. Replay of the WAL record for setting a bit in the visibility map
contained an assertion that a full-page image of that record type can only
occur with checksums enabled. But it can also happen with wal_log_hints, so
remove the assertion. Unlike checksums, wal_log_hints can be changed on the
fly, so it would be complicated to figure out if it was enabled at the time
that the WAL record was generated.

2. wal_log_hints has the same effect on the locking needed to read the LSN
of a page as data checksums. BufferGetLSNAtomic() didn't get the memo.

Backpatch to 9.4, where wal_log_hints was added.
2015-06-26 12:39:22 +03:00
Robert Haas
8364510a46 Allow background workers to connect to no particular database.
The documentation claims that this is supported, but it didn't
actually work.  Fix that.

Reported by Pavel Stehule; patch by me.
2015-06-25 16:53:59 -04:00
Tom Lane
e118555cf9 Fix the logic for putting relations into the relcache init file.
Commit f3b5565dd4e59576be4c772da364704863e6a835 was a couple of bricks shy
of a load; specifically, it missed putting pg_trigger_tgrelid_tgname_index
into the relcache init file, because that index is not used by any
syscache.  However, we have historically nailed that index into cache for
performance reasons.  The upshot was that load_relcache_init_file always
decided that the init file was busted and silently ignored it, resulting
in a significant hit to backend startup speed.

To fix, reinstantiate RelationIdIsInInitFile() as a wrapper around
RelationSupportsSysCache(), which can know about additional relations
that should be in the init file despite being unknown to syscache.c.

Also install some guards against future mistakes of this type: make
write_relcache_init_file Assert that all nailed relations get written to
the init file, and make load_relcache_init_file emit a WARNING if it takes
the "wrong number of nailed relations" exit path.  Now that we remove the
init files during postmaster startup, that case should never occur in the
field, even if we are starting a minor-version update that added or removed
rels from the nailed set.  So the warning shouldn't ever be seen by end
users, but it will show up in the regression tests if somebody breaks this
logic.

Back-patch to all supported branches, like the previous commit.
2015-06-25 14:39:05 -04:00
Tom Lane
38c6b19415 Docs: fix claim that to_char('FM') removes trailing zeroes.
Of course, what it removes is leading zeroes.  Seems to have been a thinko
in commit ffe92d15d53625d5ae0c23f4e1984ed43614a33d.  Noted by Hubert Depesz
Lubaczewski.
2015-06-25 10:44:40 -04:00
Tom Lane
d8f9ab776c Improve inheritance_planner()'s performance for large inheritance sets.
Commit c03ad5602f529787968fa3201b35c119bbc6d782 introduced a planner
performance regression for UPDATE/DELETE on large inheritance sets.
It required copying the append_rel_list (which is of size proportional to
the number of inherited tables) once for each inherited table, thus
resulting in O(N^2) time and memory consumption.  While it's difficult to
avoid that in general, the extra work only has to be done for
append_rel_list entries that actually reference subquery RTEs, which
inheritance-set entries will not.  So we can buy back essentially all of
the loss in cases without subqueries in FROM; and even for those, the added
work is mainly proportional to the number of UNION ALL subqueries.

Back-patch to 9.2, like the previous commit.

Tom Lane and Dean Rasheed, per a complaint from Thomas Munro.
2015-06-22 18:53:27 -04:00
Noah Misch
d1c1e48832 Truncate strings in tarCreateHeader() with strlcpy(), not sprintf().
This supplements the GNU libc bug #6530 workarounds introduced in commit
54cd4f04576833abc394e131288bf3dd7dcf4806.  On affected systems, a
tar-format pg_basebackup failed when some filename beneath the data
directory was not valid character data in the postmaster/walsender
locale.  Back-patch to 9.1, where pg_basebackup was introduced.  Extant,
bug-prone conversion specifications receive only ASCII bytes or involve
low-importance messages.
2015-06-21 20:04:53 -04:00
Andres Freund
ec1408155d Improve multixact emergency autovacuum logic.
Previously autovacuum was not necessarily triggered if space in the
members slru got tight. The first problem was that the signalling was
tied to values in the offsets slru, but members can advance much
faster. Thats especially a problem if old sessions had been around that
previously prevented the multixact horizon to increase. Secondly the
skipping logic doesn't work if the database was restarted after
autovacuum was triggered - that knowledge is not preserved across
restart. This is especially a problem because it's a common
panic-reaction to restart the database if it gets slow to
anti-wraparound vacuums.

Fix the first problem by separating the logic for members from
offsets. Trigger autovacuum whenever a multixact crosses a segment
boundary, as the current member offset increases in irregular values, so
we can't use a simple modulo logic as for offsets.  Add a stopgap for
the second problem, by signalling autovacuum whenver ERRORing out
because of boundaries.

Discussion: 20150608163707.GD20772@alap3.anarazel.de

Backpatch into 9.3, where it became more likely that multixacts wrap
around.
2015-06-21 19:00:30 +02:00
Andres Freund
67876a17eb Add missing check for wal_debug GUC.
9a20a9b2 added a new elog(), enabled when WAL_DEBUG is defined. The
other WAL_DEBUG dependant messages check for the wal_debug GUC, but this
one did not. While at it replace 'upto' with 'up to'.

Discussion: 20150610110253.GF3832@alap3.anarazel.de

Backpatch to 9.4, the first release containing 9a20a9b2.
2015-06-21 18:37:30 +02:00
Noah Misch
b2ed1682d4 Fix failure to copy setlocale() return value.
POSIX permits setlocale() calls to invalidate any previous setlocale()
return values, but commit 5f538ad004aa00cf0881f179f0cde789aad4f47e
neglected to account for setlocale(LC_CTYPE, NULL) doing so.  The effect
was to set the LC_CTYPE environment variable to an unintended value.
pg_perm_setlocale() sets this variable to assist PL/Perl; without it,
Perl would undo PostgreSQL's locale settings.  The known-affected
configurations are 32-bit, release builds using Visual Studio 2012 or
Visual Studio 2013.  Visual Studio 2010 is unaffected, as were all
buildfarm-attested configurations.  In principle, this bug could leave
the wrong LC_CTYPE in effect after PL/Perl use, which could in turn
facilitate problems like corrupt tsvector datums.  No known platform
experiences that consequence, because PL/Perl on Windows does not use
this environment variable.

The bug has been user-visible, as early postmaster failure, on systems
with Windows ANSI code page set to CP936 for "Chinese (Simplified, PRC)"
and probably on systems using other multibyte code pages.
(SetEnvironmentVariable() rejects values containing character data not
valid under the Windows ANSI code page.)  Back-patch to 9.4, where the
faulty commit first appeared.

Reported by Didi Hu and 林鹏程.  Reviewed by Tom Lane, though this fix
strategy was not his first choice.
2015-06-20 12:10:56 -04:00
Alvaro Herrera
b8839b3a74 Fix thinko in comment (launcher -> worker) 2015-06-20 11:45:59 -03:00
Tom Lane
29722d79b8 In immediate shutdown, postmaster should not exit till children are gone.
This adjusts commit 82233ce7ea42d6ba519aaec63008aff49da6c7af so that the
postmaster does not exit until all its child processes have exited, even
if the 5-second timeout elapses and we have to send SIGKILL.  There is no
great value in having the postmaster process quit sooner, and doing so can
mislead onlookers into thinking that the cluster is fully terminated when
actually some child processes still survive.

This effect might explain recent test failures on buildfarm member hamster,
wherein we failed to restart a cluster just after shutting it down with
"pg_ctl stop -m immediate".

I also did a bit of code review/beautification, including fixing a faulty
use of the Max() macro on a volatile expression.

Back-patch to 9.4.  In older branches, the postmaster never waited for
children to exit during immediate shutdowns, and changing that would be
too much of a behavioral change.
2015-06-19 14:23:39 -04:00
Alvaro Herrera
cf733760ea Clamp autovacuum launcher sleep time to 5 minutes
This avoids the problem that it might go to sleep for an unreasonable
amount of time in unusual conditions like the server clock moving
backwards an unreasonable amount of time.

(Simply moving the server clock forward again doesn't solve the problem
unless you wake up the autovacuum launcher manually, say by sending it
SIGHUP).

Per trouble report from Prakash Itnal in
https://www.postgresql.org/message-id/CAHC5u79-UqbapAABH2t4Rh2eYdyge0Zid-X=Xz-ZWZCBK42S0Q@mail.gmail.com

Analyzed independently by Haribabu Kommi and Tom Lane.
2015-06-19 12:44:35 -03:00
Robert Haas
8507a5b37b Fix corner case in autovacuum-forcing logic for multixact wraparound.
Since find_multixact_start() relies on SimpleLruDoesPhysicalPageExist(),
and that function looks only at the on-disk state, it's possible for it
to fail to find a page that exists in the in-memory SLRU that has not
been written yet.  If that happens, SetOffsetVacuumLimit() will
erroneously decide to force emergency autovacuuming immediately.

We should probably fix find_multixact_start() to consider the data
cached in memory as well as on the on-disk state, but that's no excuse
for SetOffsetVacuumLimit() to be stupid about the case where it can
no longer read the value after having previously succeeded in doing so.

Report by Andres Freund.
2015-06-19 11:35:44 -04:00
Michael Meskes
2a781b5bb2 Check for out of memory when allocating sqlca.
Patch by Michael Paquier
2015-06-15 14:22:24 +02:00
Michael Meskes
853222ce00 Fix memory leak in ecpglib's connect function.
Patch by Michael Paquier
2015-06-15 14:22:18 +02:00
Michael Meskes
70767ac268 Fix intoasc() in Informix compat lib. This function used to be a noop.
Patch by Michael Paquier
2015-06-13 11:05:06 +02:00
Michael Meskes
4f60d66587 Fixed some memory leaks in ECPG.
Patch by Michael Paquier
2015-06-13 11:04:58 +02:00
Tom Lane
1c150f8aa7 Improve error message and hint for ALTER COLUMN TYPE can't-cast failure.
We already tried to improve this once, but the "improved" text was rather
off-target if you had provided a USING clause.  Also, it seems helpful
to provide the exact text of a suggested USING clause, so users can just
copy-and-paste it when needed.  Per complaint from Keith Rarick and a
suggestion from Merlin Moncure.

Back-patch to 9.2 where the current wording was adopted.
2015-06-12 11:54:03 -04:00
Kevin Grittner
e9eebbaebf Fix typo in comment.
Backpatch to 9.4 to minimize possible conflicts.
2015-06-10 17:04:06 -05:00
Tom Lane
7c055f3ec3 Stamp 9.4.4. REL9_4_4 2015-06-09 15:29:38 -04:00
Tom Lane
57ec3db267 Release notes for 9.4.4, 9.3.9, 9.2.13, 9.1.18, 9.0.22. 2015-06-09 14:33:43 -04:00
Tom Lane
abdeb3504d Report more information if pg_perm_setlocale() fails at startup.
We don't know why a few Windows users have seen this fail, but the
taciturnity of the error message certainly isn't helping debug it.
Let's at least find out which LC category isn't working.
2015-06-09 13:37:08 -04:00
Andres Freund
0db10d4e92 Allow HotStandbyActiveInReplay() to be called in single user mode.
HotStandbyActiveInReplay, introduced in 061b079f, only allowed WAL
replay to happen in the startup process, missing the single user case.

This buglet is fairly harmless as it only causes problems when single
user mode in an assertion enabled build is used to replay a btree vacuum
record.

Backpatch to 9.2. 061b079f was backpatched further, but the assertion
was not.
2015-06-08 14:09:46 +02:00
Tom Lane
be25a08a91 Use a safer method for determining whether relcache init file is stale.
When we invalidate the relcache entry for a system catalog or index, we
must also delete the relcache "init file" if the init file contains a copy
of that rel's entry.  The old way of doing this relied on a specially
maintained list of the OIDs of relations present in the init file: we made
the list either when reading the file in, or when writing the file out.
The problem is that when writing the file out, we included only rels
present in our local relcache, which might have already suffered some
deletions due to relcache inval events.  In such cases we correctly decided
not to overwrite the real init file with incomplete data --- but we still
used the incomplete initFileRelationIds list for the rest of the current
session.  This could result in wrong decisions about whether the session's
own actions require deletion of the init file, potentially allowing an init
file created by some other concurrent session to be left around even though
it's been made stale.

Since we don't support changing the schema of a system catalog at runtime,
the only likely scenario in which this would cause a problem in the field
involves a "vacuum full" on a catalog concurrently with other activity, and
even then it's far from easy to provoke.  Remarkably, this has been broken
since 2002 (in commit 786340441706ac1957a031f11ad1c2e5b6e18314), but we had
never seen a reproducible test case until recently.  If it did happen in
the field, the symptoms would probably involve unexpected "cache lookup
failed" errors to begin with, then "could not open file" failures after the
next checkpoint, as all accesses to the affected catalog stopped working.
Recovery would require manually removing the stale "pg_internal.init" file.

To fix, get rid of the initFileRelationIds list, and instead consult
syscache.c's list of relations used in catalog caches to decide whether a
relation is included in the init file.  This should be a tad more efficient
anyway, since we're replacing linear search of a list with ~100 entries
with a binary search.  It's a bit ugly that the init file contents are now
so directly tied to the catalog caches, but in practice that won't make
much difference.

Back-patch to all supported branches.
2015-06-07 15:32:09 -04:00
Tom Lane
247263dc33 Fix incorrect order of database-locking operations in InitPostgres().
We should set MyProc->databaseId after acquiring the per-database lock,
not beforehand.  The old way risked deadlock against processes trying to
copy or delete the target database, since they would first acquire the lock
and then wait for processes with matching databaseId to exit; that left a
window wherein an incoming process could set its databaseId and then block
on the lock, while the other process had the lock and waited in vain for
the incoming process to exit.

CountOtherDBBackends() would time out and fail after 5 seconds, so this
just resulted in an unexpected failure not a permanent lockup, but it's
still annoying when it happens.  A real-world example of a use-case is that
short-duration connections to a template database should not cause CREATE
DATABASE to fail.

Doing it in the other order should be fine since the contract has always
been that processes searching the ProcArray for a database ID must hold the
relevant per-database lock while searching.  Thus, this actually removes
the former race condition that required an assumption that storing to
MyProc->databaseId is atomic.

It's been like this for a long time, so back-patch to all active branches.
2015-06-05 13:22:27 -04:00