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2014-05-15Fix race condition in preparing a transaction for two-phase commit.Heikki Linnakangas
To lock a prepared transaction's shared memory entry, we used to mark it with the XID of the backend. When the XID was no longer active according to the proc array, the entry was implicitly considered as not locked anymore. However, when preparing a transaction, the backend's proc array entry was cleared before transfering the locks (and some other state) to the prepared transaction's dummy PGPROC entry, so there was a window where another backend could finish the transaction before it was in fact fully prepared. To fix, rewrite the locking mechanism of global transaction entries. Instead of an XID, just have simple locked-or-not flag in each entry (we store the locking backend's backend id rather than a simple boolean, but that's just for debugging purposes). The backend is responsible for explicitly unlocking the entry, and to make sure that that happens, install a callback to unlock it on abort or process exit. Backpatch to all supported versions.
2014-05-14In initdb, ensure stdout/stderr buffering behavior is what we expect.Tom Lane
Since this program may print to either stdout or stderr, the relative ordering of its messages depends on the buffering behavior of those files. Force stdout to be line-buffered and stderr to be unbuffered, ensuring that the behavior will match standard Unix interactive behavior, even when stdout and stderr are rerouted to a file. Per complaint from Tomas Vondra. The particular case he pointed out is new in HEAD, but issues of the same sort could arise in any branch with other error messages, so back-patch to all branches. I'm unsure whether we might not want to do this in other client programs as well. For the moment, just fix initdb.
2014-05-12Ignore config.pl and buildenv.pl in src/tools/msvc.Tom Lane
config.pl and buildenv.pl can be used to customize build settings when using MSVC. They should never get committed into the common source tree. Back-patch to 9.0; it looks like the rules were different in 8.4. Michael Paquier
2014-05-08Un-break ecpg test suite under --disable-integer-datetimes.Noah Misch
Commit 4318daecc959886d001a6e79c6ea853e8b1dfb4b broke it. The change in sub-second precision at extreme dates is normal. The inconsistent truncation vs. rounding is essentially a bug, albeit a longstanding one. Back-patch to 8.4, like the causative commit.
2014-05-08Protect against torn pages when deleting GIN list pages.Heikki Linnakangas
To-be-deleted list pages contain no useful information, as they are being deleted, but we must still protect the writes from being torn by a crash after a partial write. To do that, re-initialize the pages on WAL replay. Jeff Janes caught this with a test program to test partial writes. Backpatch to all supported versions.
2014-05-08Include files copied from libpqport in .gitignoreHeikki Linnakangas
Michael Paquier
2014-05-07Avoid buffer bloat in libpq when server is consistently faster than client.Tom Lane
If the server sends a long stream of data, and the server + network are consistently fast enough to force the recv() loop in pqReadData() to iterate until libpq's input buffer is full, then upon processing the last incomplete message in each bufferload we'd usually double the buffer size, due to supposing that we didn't have enough room in the buffer to finish collecting that message. After filling the newly-enlarged buffer, the cycle repeats, eventually resulting in an out-of-memory situation (which would be reported misleadingly as "lost synchronization with server"). Of course, we should not enlarge the buffer unless we still need room after discarding already-processed messages. This bug dates back quite a long time: pqParseInput3 has had the behavior since perhaps 2003, getCopyDataMessage at least since commit 70066eb1a1ad in 2008. Probably the reason it's not been isolated before is that in common environments the recv() loop would always be faster than the server (if on the same machine) or faster than the network (if not); or at least it wouldn't be slower consistently enough to let the buffer ramp up to a problematic size. The reported cases involve Windows, which perhaps has different timing behavior than other platforms. Per bug #7914 from Shin-ichi Morita, though this is different from his proposed solution. Back-patch to all supported branches.
2014-05-07Fix failure to set ActiveSnapshot while rewinding a cursor.Tom Lane
ActiveSnapshot needs to be set when we call ExecutorRewind because some plan node types may execute user-defined functions during their ReScan calls (nodeLimit.c does so, at least). The wisdom of that is somewhat debatable, perhaps, but for now the simplest fix is to make sure the required context is valid. Failure to do this typically led to a null-pointer-dereference core dump, though it's possible that in more complex cases a function could be executed with the wrong snapshot leading to very subtle misbehavior. Per report from Leif Jensen. It's been broken for a long time, so back-patch to all active branches.
2014-05-06Fix interval test, which was broken for floating-point timestamps.Jeff Davis
Commit 4318daecc959886d001a6e79c6ea853e8b1dfb4b introduced a test that couldn't be made consistent between integer and floating-point timestamps. It was designed to test the longest possible interval output length, so removing four zeros from the number of hours, as this patch does, is not ideal. But the test still has some utility for its original purpose, and there aren't a lot of other good options. Noah Misch suggested a different approach where we test that the output either matches what we expect from integer timestamps or what we expect from floating-point timestamps. That seemed to obscure an otherwise simple test, however. Reviewed by Tom Lane and Noah Misch.
2014-05-06Remove tabs after spaces in C commentsBruce Momjian
This was not changed in HEAD, but will be done later as part of a pgindent run. Future pgindent runs will also do this. Report by Tom Lane Backpatch through all supported branches, but not HEAD
2014-05-06Fix use of free in walsender error handling after a sysid mismatch.Heikki Linnakangas
Found via valgrind. The bug exists since the introduction of the walsender, so backpatch to 9.0. Andres Freund
2014-05-06Fix handling of array of char pointers in ecpglib.Michael Meskes
When array of char * was used as target for a FETCH statement returning more than one row, it tried to store all the result in the first element. Instead it should dump array of char pointers with right offset, use the address instead of the value of the C variable while reading the array and treat such variable as char **, instead of char * for pointer arithmetic. Patch by Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>
2014-05-05Fix possible cache invalidation failure in ReceiveSharedInvalidMessages.Tom Lane
Commit fad153ec45299bd4d4f29dec8d9e04e2f1c08148 modified sinval.c to reduce the number of calls into sinvaladt.c (which require taking a shared lock) by keeping a local buffer of collected-but-not-yet-processed messages. However, if processing of the last message in a batch resulted in a recursive call to ReceiveSharedInvalidMessages, we could overwrite that message with a new one while the outer invalidation function was still working on it. This would be likely to lead to invalidation of the wrong cache entry, allowing subsequent processing to use stale cache data. The fix is just to make a local copy of each message while we're processing it. Spotted by Andres Freund. Back-patch to 8.4 where the bug was introduced.
2014-05-01Fix failure to detoast fields in composite elements of structured types.Tom Lane
If we have an array of records stored on disk, the individual record fields cannot contain out-of-line TOAST pointers: the tuptoaster.c mechanisms are only prepared to deal with TOAST pointers appearing in top-level fields of a stored row. The same applies for ranges over composite types, nested composites, etc. However, the existing code only took care of expanding sub-field TOAST pointers for the case of nested composites, not for other structured types containing composites. For example, given a command such as UPDATE tab SET arraycol = ARRAY[(ROW(x,42)::mycompositetype] ... where x is a direct reference to a field of an on-disk tuple, if that field is long enough to be toasted out-of-line then the TOAST pointer would be inserted as-is into the array column. If the source record for x is later deleted, the array field value would become a dangling pointer, leading to errors along the line of "missing chunk number 0 for toast value ..." when the value is referenced. A reproducible test case for this was provided by Jan Pecek, but it seems likely that some of the "missing chunk number" reports we've heard in the past were caused by similar issues. Code-wise, the problem is that PG_DETOAST_DATUM() is not adequate to produce a self-contained Datum value if the Datum is of composite type. Seen in this light, the problem is not just confined to arrays and ranges, but could also affect some other places where detoasting is done in that way, for example form_index_tuple(). I tried teaching the array code to apply toast_flatten_tuple_attribute() along with PG_DETOAST_DATUM() when the array element type is composite, but this was messy and imposed extra cache lookup costs whether or not any TOAST pointers were present, indeed sometimes when the array element type isn't even composite (since sometimes it takes a typcache lookup to find that out). The idea of extending that approach to all the places that currently use PG_DETOAST_DATUM() wasn't attractive at all. This patch instead solves the problem by decreeing that composite Datum values must not contain any out-of-line TOAST pointers in the first place; that is, we expand out-of-line fields at the point of constructing a composite Datum, not at the point where we're about to insert it into a larger tuple. This rule is applied only to true composite Datums, not to tuples that are being passed around the system as tuples, so it's not as invasive as it might sound at first. With this approach, the amount of code that has to be touched for a full solution is greatly reduced, and added cache lookup costs are avoided except when there actually is a TOAST pointer that needs to be inlined. The main drawback of this approach is that we might sometimes dereference a TOAST pointer that will never actually be used by the query, imposing a rather large cost that wasn't there before. On the other side of the coin, if the field value is used multiple times then we'll come out ahead by avoiding repeat detoastings. Experimentation suggests that common SQL coding patterns are unaffected either way, though. Applications that are very negatively affected could be advised to modify their code to not fetch columns they won't be using. In future, we might consider reverting this solution in favor of detoasting only at the point where data is about to be stored to disk, using some method that can drill down into multiple levels of nested structured types. That will require defining new APIs for structured types, though, so it doesn't seem feasible as a back-patchable fix. Note that this patch changes HeapTupleGetDatum() from a macro to a function call; this means that any third-party code using that macro will not get protection against creating TOAST-pointer-containing Datums until it's recompiled. The same applies to any uses of PG_RETURN_HEAPTUPLEHEADER(). It seems likely that this is not a big problem in practice: most of the tuple-returning functions in core and contrib produce outputs that could not possibly be toasted anyway, and the same probably holds for third-party extensions. This bug has existed since TOAST was invented, so back-patch to all supported branches.
2014-04-30Check for interrupts and stack overflow during rule/view dumps.Tom Lane
Since ruleutils.c recurses, it could be driven to stack overflow by deeply nested constructs. Very large queries might also take long enough to deparse that a check for interrupts seems like a good idea. Stick appropriate tests into a couple of key places. Noted by Greg Stark. Back-patch to all supported branches.
2014-04-30Add missing SYSTEMQUOTEsHeikki Linnakangas
Some popen() calls were missing SYSTEMQUOTEs, which caused initdb and pg_upgrade to fail on Windows, if the installation path contained both spaces and @ signs. Patch by Nikhil Deshpande. Backpatch to all supported versions.
2014-04-28Fix two bugs in WAL-logging of GIN pending-list pages.Heikki Linnakangas
In writeListPage, never take a full-page image of the page, because we have all the information required to re-initialize in the WAL record anyway. Before this fix, a full-page image was always generated, unless full_page_writes=off, because when the page is initialized its LSN is always 0. In stable-branches, keep the code to restore the backup blocks if they exist, in case that the WAL is generated with an older minor version, but in master Assert that there are no full-page images. In the redo routine, add missing "off++". Otherwise the tuples are added to the page in reverse order. That happens to be harmless because we always scan and remove all the tuples together, but it was clearly wrong. Also, it was masked by the first bug unless full_page_writes=off, because the page was always restored from a full-page image. Backpatch to all supported versions.
2014-04-24Reset pg_stat_activity.xact_start during PREPARE TRANSACTION.Tom Lane
Once we've completed a PREPARE, our session is not running a transaction, so its entry in pg_stat_activity should show xact_start as null, rather than leaving the value as the start time of the now-prepared transaction. I think possibly this oversight was triggered by faulty extrapolation from the adjacent comment that says PrepareTransaction should not call AtEOXact_PgStat, so tweak the wording of that comment. Noted by Andres Freund while considering bug #10123 from Maxim Boguk, although this error doesn't seem to explain that report. Back-patch to all active branches.
2014-04-23Fix incorrect pg_proc.proallargtypes entries for two built-in functions.Tom Lane
pg_sequence_parameters() and pg_identify_object() have had incorrect proallargtypes entries since 9.1 and 9.3 respectively. This was mostly masked by the correct information in proargtypes, but a few operations such as pg_get_function_arguments() (and thus psql's \df display) would show the wrong data types for these functions' input parameters. In HEAD, fix the wrong info, bump catversion, and add an opr_sanity regression test to catch future mistakes of this sort. In the back branches, just fix the wrong info so that installations initdb'd with future minor releases will have the right data. We can't force an initdb, and it doesn't seem like a good idea to add a regression test that will fail on existing installations. Andres Freund
2014-04-23Fix typos in comment.Heikki Linnakangas
2014-04-17Fix unused-variable warning on Windows.Tom Lane
Introduced in 585bca39: msgid is not used in the Windows code path. Also adjust comments a tad (mostly to keep pgindent from messing it up). David Rowley
2014-04-16Attempt to get plpython regression tests working again for MSVC builds.Andrew Dunstan
This has probably been broken for quite a long time. Buildfarm member currawong's current results suggest that it's been broken since 9.1, so backpatch this to that branch. This only supports Python 2 - I will handle Python 3 separately, but this is a fairly simple fix.
2014-04-16Use AF_UNSPEC not PF_UNSPEC in getaddrinfo calls.Tom Lane
According to the Single Unix Spec and assorted man pages, you're supposed to use the constants named AF_xxx when setting ai_family for a getaddrinfo call. In a few places we were using PF_xxx instead. Use of PF_xxx appears to be an ancient BSD convention that was not adopted by later standardization. On BSD and most later Unixen, it doesn't matter much because those constants have equivalent values anyway; but nonetheless this code is not per spec. In the same vein, replace PF_INET by AF_INET in one socket() call, which wasn't even consistent with the other socket() call in the same function let alone the remainder of our code. Per investigation of a Cygwin trouble report from Marco Atzeri. It's probably a long shot that this will fix his issue, but it's wrong in any case.
2014-04-16Fix timeout in LDAP lookup of libpq connection parametersMagnus Hagander
Bind attempts to an LDAP server should time out after two seconds, allowing additional lines in the service control file to be parsed (which provide a fall back to a secondary LDAP server or default options). The existing code failed to enforce that timeout during TCP connect, resulting in a hang far longer than two seconds if the LDAP server does not respond. Laurenz Albe
2014-04-16check socket creation errors against PGINVALID_SOCKETBruce Momjian
Previously, in some places, socket creation errors were checked for negative values, which is not true for Windows because sockets are unsigned. This masked socket creation errors on Windows. Backpatch through 9.0. 8.4 doesn't have the infrastructure to fix this.
2014-04-16Use correctly-sized buffer when zero-filling a WAL file.Heikki Linnakangas
I mixed up BLCKSZ and XLOG_BLCKSZ when I changed the way the buffer is allocated a couple of weeks ago. With the default settings, they are both 8k, but they can be changed at compile-time.
2014-04-09Several fixes to array handling in ecpg.Michael Meskes
Patches by Ashutosh Bapat <ashutosh.bapat@enterprisedb.com> Conflicts: src/interfaces/ecpg/test/expected/preproc-outofscope.c
2014-04-08Fix hot standby bug with GiST scans.Heikki Linnakangas
Don't reset the rightlink of a page when replaying a page update record. This was a leftover from pre-hot standby days, when it was not possible to have scans concurrent with WAL replay. Resetting the right-link was not necessary back then either, but it was done for the sake of tidiness. But with hot standby, it's wrong, because a concurrent scan might still need it. Backpatch all versions with hot standby, 9.0 and above.
2014-04-05Block signals earlier during postmaster startup.Tom Lane
Formerly, we set up the postmaster's signal handling only when we were about to start launching subprocesses. This is a bad idea though, as it means that for example a SIGINT arriving before that will kill the postmaster instantly, perhaps leaving lockfiles, socket files, shared memory, etc laying about. We'd rather that such a signal caused orderly postmaster termination including releasing of those resources. A simple fix is to move the PostmasterMain stanza that initializes signal handling to an earlier point, before we've created any such resources. Then, an early-arriving signal will be blocked until we're ready to deal with it in the usual way. (The only part that really needs to be moved up is blocking of signals, but it seems best to keep the signal handler installation calls together with that; for one thing this ensures the kernel won't drop any signals we wished to get. The handlers won't get invoked in any case until we unblock signals in ServerLoop.) Per a report from MauMau. He proposed changing the way "pg_ctl stop" works to deal with this, but that'd just be masking one symptom not fixing the core issue. It's been like this since forever, so back-patch to all supported branches.
2014-04-05Fix processing of PGC_BACKEND GUC parameters on Windows.Tom Lane
EXEC_BACKEND builds (i.e., Windows) failed to absorb values of PGC_BACKEND parameters if they'd been changed post-startup via the config file. This for example prevented log_connections from working if it were turned on post-startup. The mechanism for handling this case has always been a bit of a kluge, and it wasn't revisited when we implemented EXEC_BACKEND. While in a normal forking environment new backends will inherit the postmaster's value of such settings, EXEC_BACKEND backends have to read the settings from the CONFIG_EXEC_PARAMS file, and they were mistakenly rejecting them. So this case has always been broken in the Windows port; so back-patch to all supported branches. Amit Kapila
2014-04-04Fix tablespace creation WAL replay to work on Windows.Tom Lane
The code segment that removes the old symlink (if present) wasn't clued into the fact that on Windows, symlinks are junction points which have to be removed with rmdir(). Backpatch to 9.0, where the failing code was introduced. MauMau, reviewed by Muhammad Asif Naeem and Amit Kapila
2014-04-04Avoid allocations in critical sections.Heikki Linnakangas
If a palloc in a critical section fails, it becomes a PANIC.
2014-04-03Avoid palloc in critical section in GiST WAL-logging.Heikki Linnakangas
Memory allocation can fail if you run out of memory, and inside a critical section that will lead to a PANIC. Use conservatively-sized arrays in stack instead. There was previously no explicit limit on the number of pages a GiST split can produce, it was only limited by the number of LWLocks that can be held simultaneously (100 at the moment). This patch adds an explicit limit of 75 pages. That should be plenty, a typical split shouldn't produce more than 2-3 page halves. The bug has been there forever, but only backpatch down to 9.1. The code was changed significantly in 9.1, and it doesn't seem worth the risk or trouble to adapt this for 9.0 and 8.4.
2014-04-02Fix assorted issues in client host name lookup.Tom Lane
The code for matching clients to pg_hba.conf lines that specify host names (instead of IP address ranges) failed to complain if reverse DNS lookup failed; instead it silently didn't match, so that you might end up getting a surprising "no pg_hba.conf entry for ..." error, as seen in bug #9518 from Mike Blackwell. Since we don't want to make this a fatal error in situations where pg_hba.conf contains a mixture of host names and IP addresses (clients matching one of the numeric entries should not have to have rDNS data), remember the lookup failure and mention it as DETAIL if we get to "no pg_hba.conf entry". Apply the same approach to forward-DNS lookup failures, too, rather than treating them as immediate hard errors. Along the way, fix a couple of bugs that prevented us from detecting an rDNS lookup error reliably, and make sure that we make only one rDNS lookup attempt; formerly, if the lookup attempt failed, the code would try again for each host name entry in pg_hba.conf. Since more or less the whole point of this design is to ensure there's only one lookup attempt not one per entry, the latter point represents a performance bug that seems sufficient justification for back-patching. Also, adjust src/port/getaddrinfo.c so that it plays as well as it can with this code. Which is not all that well, since it does not have actual support for rDNS lookup, but at least it should return the expected (and required by spec) error codes so that the main code correctly perceives the lack of functionality as a lookup failure. It's unlikely that PG is still being used in production on any machines that require our getaddrinfo.c, so I'm not excited about working harder than this. To keep the code in the various branches similar, this includes back-patching commits c424d0d1052cb4053c8712ac44123f9b9a9aa3f2 and 1997f34db4687e671690ed054c8f30bb501b1168 into 9.2 and earlier. Back-patch to 9.1 where the facility for hostnames in pg_hba.conf was introduced.
2014-04-01Fix bugs in manipulation of PgBackendStatus.st_clienthostname.Tom Lane
Initialization of this field was not being done according to the st_changecount protocol (it has to be done within the changecount increment range, not outside). And the test to see if the value should be reported as null was wrong. Noted while perusing uses of Port.remote_hostname. This was wrong from the introduction of this code (commit 4a25bc145), so back-patch to 9.1.
2014-03-29Revert "Secure Unix-domain sockets of "make check" temporary clusters."Noah Misch
About half of the buildfarm members use too-long directory names, strongly suggesting that this approach is a dead end.
2014-03-29Secure Unix-domain sockets of "make check" temporary clusters.Noah Misch
Any OS user able to access the socket can connect as the bootstrap superuser and in turn execute arbitrary code as the OS user running the test. Protect against that by placing the socket in the temporary data directory, which has mode 0700 thanks to initdb. Back-patch to 8.4 (all supported versions). The hazard remains wherever the temporary cluster accepts TCP connections, notably on Windows. Attempts to run "make check" from a directory with a long name will now fail. An alternative not sharing that problem was to place the socket in a subdirectory of /tmp, but that is only secure if /tmp is sticky. The PG_REGRESS_SOCK_DIR environment variable is available as a workaround when testing from long directory paths. As a convenient side effect, this lets testing proceed smoothly in builds that override DEFAULT_PGSOCKET_DIR. Popular non-default values like /var/run/postgresql are often unwritable to the build user. Security: CVE-2014-0067
2014-03-26Fix refcounting bug in PLy_modify_tuple().Tom Lane
We must increment the refcount on "plntup" as soon as we have the reference, not sometime later. Otherwise, if an error is thrown in between, the Py_XDECREF(plntup) call in the PG_CATCH block removes a refcount we didn't add, allowing the object to be freed even though it's still part of the plpython function's parsetree. This appears to be the cause of crashes seen on buildfarm member prairiedog. It's a bit surprising that we've not seen it fail repeatably before, considering that the regression tests have been exercising the faulty code path since 2009. The real-world impact is probably minimal, since it's unlikely anyone would be provoking the "TD["new"] is not a dictionary" error in production, and that's the only case that is actually wrong. Still, it's a bug affecting the regression tests, so patch all supported branches. In passing, remove dead variable "plstr", and demote "platt" to a local variable inside the PG_TRY block, since we don't need to clean it up in the PG_CATCH path.
2014-03-26Don't forget to flush XLOG_PARAMETER_CHANGE record.Fujii Masao
Backpatch to 9.0 where XLOG_PARAMETER_CHANGE record was instroduced.
2014-03-21Properly check for readdir/closedir() failuresBruce Momjian
Clear errno before calling readdir() and handle old MinGW errno bug while adding full test coverage for readdir/closedir failures. Backpatch through 8.4.
2014-03-17Stamp 9.1.13.REL9_1_13Tom Lane
2014-03-17Fix bug in clean shutdown of walsender that pg_receiving is connecting to.Fujii Masao
On clean shutdown, walsender waits for all WAL to be replicated to a standby, and exits. It determined whether that replication had been completed by checking whether its sent location had been equal to a standby's flush location. Unfortunately this condition never becomes true when the standby such as pg_receivexlog which always returns an invalid flush location is connecting to walsender, and then walsender waits forever. This commit changes walsender so that it just checks a standby's write location if a flush location is invalid. Back-patch to 9.1 where enough infrastructure for this exists.
2014-03-16plperl: Fix memory leak in hek2cstrAlvaro Herrera
Backpatch all the way back to 9.1, where it was introduced by commit 50d89d42. Reported by Sergey Burladyan in #9223 Author: Alex Hunsaker
2014-03-16Translation updatesPeter Eisentraut
2014-03-16Fix advertised dispsize for libpq's sslmode connection parameter.Tom Lane
"8" was correct back when "disable" was the longest allowed value, but since "verify-full" was added, it should be "12". Given the lack of complaints, I wouldn't be surprised if nobody is actually using these values ... but still, if they're in the API, they should be right. Noticed while pursuing a different problem. It's been wrong for quite a long time, so back-patch to all supported branches.
2014-03-16Disable RandomizeBaseAddress on MSVC buildsMagnus Hagander
This is a backpatch of 7f3e17b4827b61ad84e0774e3e43da4c57c4487f to 9.0 and 9.1. Patch by MauMau
2014-03-15Update time zone data files to tzdata release 2014a.Tom Lane
DST law changes in Fiji, Turkey; historical changes in Israel, Ukraine.
2014-03-13Prevent interrupts while reporting non-ERROR elog messages.Tom Lane
This should eliminate the risk of recursive entry to syslog(3), which appears to be the cause of the hang reported in bug #9551 from James Morton. Arguably, the real problem here is auth.c's willingness to turn on ImmediateInterruptOK while executing fairly wide swaths of backend code. We may well need to work at narrowing the code ranges in which the authentication_timeout interrupt is enabled. For the moment, though, this is a cheap and reasonably noninvasive fix for a field-reported failure; the other approach would be complex and not necessarily bug-free itself. Back-patch to all supported branches.
2014-03-13Avoid transaction-commit race condition while receiving a NOTIFY message.Tom Lane
Use TransactionIdIsInProgress, then TransactionIdDidCommit, to distinguish whether a NOTIFY message's originating transaction is in progress, committed, or aborted. The previous coding could accept a message from a transaction that was still in-progress according to the PGPROC array; if the client were fast enough at starting a new transaction, it might fail to see table rows added/updated by the message-sending transaction. Which of course would usually be the point of receiving the message. We noted this type of race condition long ago in tqual.c, but async.c overlooked it. The race condition probably cannot occur unless there are multiple NOTIFY senders in action, since an individual backend doesn't send NOTIFY signals until well after it's done committing. But if two senders commit in close succession, it's certainly possible that we could see the second sender's message within the race condition window while responding to the signal from the first one. Per bug #9557 from Marko Tiikkaja. This patch is slightly more invasive than what he proposed, since it removes the now-redundant TransactionIdDidAbort call. Back-patch to 9.0, where the current NOTIFY implementation was introduced.
2014-03-12In WAL replay, restore GIN metapage unconditionally to avoid torn page.Heikki Linnakangas
We don't take a full-page image of the GIN metapage; instead, the WAL record contains all the information required to reconstruct it from scratch. But to avoid torn page hazards, we must re-initialize it from the WAL record every time, even if it already has a greater LSN, similar to how normal full page images are restored. This was highly unlikely to cause any problems in practice, because the GIN metapage is small. We rely on an update smaller than a 512 byte disk sector to be atomic elsewhere, at least in pg_control. But better safe than sorry, and this would be easy to overlook if more fields are added to the metapage so that it's no longer small. Reported by Noah Misch. Backpatch to all supported versions.