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* Support JSON negative array subscripts everywhereAndrew Dunstan2015-07-17
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Previously, there was an inconsistency across json/jsonb operators that operate on datums containing JSON arrays -- only some operators supported negative array count-from-the-end subscripting. Specifically, only a new-to-9.5 jsonb deletion operator had support (the new "jsonb - integer" operator). This inconsistency seemed likely to be counter-intuitive to users. To fix, allow all places where the user can supply an integer subscript to accept a negative subscript value, including path-orientated operators and functions, as well as other extraction operators. This will need to be called out as an incompatibility in the 9.5 release notes, since it's possible that users are relying on certain established extraction operators changed here yielding NULL in the event of a negative subscript. For the json type, this requires adding a way of cheaply getting the total JSON array element count ahead of time when parsing arrays with a negative subscript involved, necessitating an ad-hoc lex and parse. This is followed by a "conversion" from a negative subscript to its equivalent positive-wise value using the count. From there on, it's as if a positive-wise value was originally provided. Note that there is still a minor inconsistency here across jsonb deletion operators. Unlike the aforementioned new "-" deletion operator that accepts an integer on its right hand side, the new "#-" path orientated deletion variant does not throw an error when it appears like an array subscript (input that could be recognized by as an integer literal) is being used on an object, which is wrong-headed. The reason for not being stricter is that it could be the case that an object pair happens to have a key value that looks like an integer; in general, these two possibilities are impossible to differentiate with rhs path text[] argument elements. However, we still don't allow the "#-" path-orientated deletion operator to perform array-style subscripting. Rather, we just return the original left operand value in the event of a negative subscript (which seems analogous to how the established "jsonb/json #> text[]" path-orientated operator may yield NULL in the event of an invalid subscript). In passing, make SetArrayPath() stricter about not accepting cases where there is trailing non-numeric garbage bytes rather than a clean NUL byte. This means, for example, that strings like "10e10" are now not accepted as an array subscript of 10 by some new-to-9.5 path-orientated jsonb operators (e.g. the new #- operator). Finally, remove dead code for jsonb subscript deletion; arguably, this should have been done in commit b81c7b409. Peter Geoghegan and Andrew Dunstan
* Add new function pg_notification_queue_usage.Robert Haas2015-07-17
| | | | | | | This tells you what fraction of NOTIFY's queue is currently filled. Brendan Jurd, reviewed by Merlin Moncure and Gurjeet Singh. A few further tweaks by me.
* Fix a low-probability crash in our qsort implementation.Tom Lane2015-07-16
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | It's standard for quicksort implementations, after having partitioned the input into two subgroups, to recurse to process the smaller partition and then handle the larger partition by iterating. This method guarantees that no more than log2(N) levels of recursion can be needed. However, Bentley and McIlroy argued that checking to see which partition is smaller isn't worth the cycles, and so their code doesn't do that but just always recurses on the left partition. In most cases that's fine; but with worst-case input we might need O(N) levels of recursion, and that means that qsort could be driven to stack overflow. Such an overflow seems to be the only explanation for today's report from Yiqing Jin of a SIGSEGV in med3_tuple while creating an index of a couple billion entries with a very large maintenance_work_mem setting. Therefore, let's spend the few additional cycles and lines of code needed to choose the smaller partition for recursion. Also, fix up the qsort code so that it properly uses size_t not int for some intermediate values representing numbers of items. This would only be a live risk when sorting more than INT_MAX bytes (in qsort/qsort_arg) or tuples (in qsort_tuple), which I believe would never happen with any caller in the current core code --- but perhaps it could happen with call sites in third-party modules? In any case, this is trouble waiting to happen, and the corrected code is probably if anything shorter and faster than before, since it removes sign-extension steps that had to happen when converting between int and size_t. In passing, move a couple of CHECK_FOR_INTERRUPTS() calls so that it's not necessary to preserve the value of "r" across them, and prettify the output of gen_qsort_tuple.pl a little. Back-patch to all supported branches. The odds of hitting this issue are probably higher in 9.4 and up than before, due to the new ability to allocate sort workspaces exceeding 1GB, but there's no good reason to believe that it's impossible to crash older branches this way.
* Fix spelling errorMagnus Hagander2015-07-16
| | | | David Rowley
* Fix copy/past error in commentMagnus Hagander2015-07-16
| | | | David Christensen
* AIX: Link the postgres executable with -Wl,-brtllib.Noah Misch2015-07-15
| | | | | | | | | This allows PostgreSQL modules and their dependencies to have undefined symbols, resolved at runtime. Perl module shared objects rely on that in Perl 5.8.0 and later. This fixes the crash when PL/PerlU loads such modules, as the hstore_plperl test suite does. Module authors can link using -Wl,-G to permit undefined symbols; by default, linking will fail as it has. Back-patch to 9.0 (all supported versions).
* Fix event trigger support for the new ALTER OPERATOR command.Heikki Linnakangas2015-07-14
| | | | | Also, the lock on pg_operator should not be released until end of transaction.
* Add ALTER OPERATOR command, for changing selectivity estimator functions.Heikki Linnakangas2015-07-14
| | | | | | | | | Other options cannot be changed, as it's not totally clear if cached plans would need to be invalidated if one of the other options change. Selectivity estimator functions only change plan costs, not correctness of plans, so those should be safe. Original patch by Uriy Zhuravlev, heavily edited by me.
* Retain comments on indexes and constraints at ALTER TABLE ... TYPE ...Heikki Linnakangas2015-07-14
| | | | | | | | | | | | | | | When a column's datatype is changed, ATExecAlterColumnType() rebuilds all the affected indexes and constraints, and the comments from the old indexes/constraints were not carried over. To fix, create a synthetic COMMENT ON command in the work queue, to re-add any comments on constraints. For indexes, there's a comment field in IndexStmt that is used. This fixes bug #13126, reported by Kirill Simonov. Original patch by Michael Paquier, reviewed by Petr Jelinek and me. This bug is present in all versions, but only backpatch to 9.5. Given how minor the issue is, it doesn't seem worth the work and risk to backpatch further than that.
* Reformat code in ATPostAlterTypeParse.Heikki Linnakangas2015-07-14
| | | | | | | | | | | The code in ATPostAlterTypeParse was very deeply indented, mostly because there were two nested switch-case statements, which add a lot of indentation. Use if-else blocks instead, to make the code less indented and more readable. This is in preparation for next patch that makes some actualy changes to the function. These cosmetic parts have been separated to make it easier to see the real changes in the other patch.
* For consistency add a pfree to ON CONFLICT set_plan_refs code.Andres Freund2015-07-12
| | | | | | Backpatch to 9.5 where ON CONFLICT was introduced. Author: Peter Geoghegan
* Add now-required #include.Tom Lane2015-07-11
| | | | Fixes compiler warning induced by 808ea8fc7bb259ddd810353719cac66e85a608c8.
* Add assign_expr_collations() to CreatePolicy() and AlterPolicy().Joe Conway2015-07-11
| | | | | | As noted by Noah Misch, CreatePolicy() and AlterPolicy() omit to call assign_expr_collations() on the node trees. Fix the omission and add his test case to the rowsecurity regression test.
* Fix postmaster's handling of a startup-process crash.Tom Lane2015-07-09
| | | | | | | | | | | | | | | | | | | | | | | 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.
* Make wal_compression PGC_SUSET rather than PGC_USERSET.Fujii Masao2015-07-09
| | | | | | | | | | | | | When enabling wal_compression, there is a risk to leak data similarly to the BREACH and CRIME attacks on SSL where the compression ratio of a full page image gives a hint of what is the existing data of this page. This vulnerability is quite cumbersome to exploit in practice, but doable. So this patch makes wal_compression PGC_SUSET in order to prevent non-superusers from enabling it and exploiting the vulnerability while DBA thinks the risk very seriously and disables it in postgresql.conf. Back-patch to 9.5 where wal_compression was introduced.
* Add .gitignore entries for AIX-specific intermediate build artifacts.Noah Misch2015-07-08
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* Revoke support for strxfrm() that write past the specified array length.Noah Misch2015-07-08
| | | | | | | This formalizes a decision implicit in commit 4ea51cdfe85ceef8afabceb03c446574daa0ac23 and adds clean detection of affected systems. Vendor updates are available for each such known bug. Back-patch to 9.5, where the aforementioned commit first appeared.
* Fix logical decoding bug leading to inefficient reopening of files.Andres Freund2015-07-07
| | | | | | | | | | | | | | | | | | | | 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.
* Make RLS related error messages more consistent and compliant.Joe Conway2015-07-06
| | | | Also updated regression expected output to match. Noted and patch by Daniele Varrazzo.
* Call getsockopt() on the correct socket.Heikki Linnakangas2015-07-06
| | | | | | | | | We're interested in the buffer size of the socket that's connected to the client, not the one that's listening for new connections. It happened to work, as default buffer size is the same on both, but it was clearly not wrong. Spotted by Tom Lane
* Don't set SO_SNDBUF on recent Windows versions that have a bigger default.Heikki Linnakangas2015-07-06
| | | | | | | | | | It's unnecessary to set it if the default is higher in the first place. Furthermore, setting SO_SNDBUF disables the so-called "dynamic send buffering" feature, which hurts performance further. This can be seen especially when the network between the client and the server has high latency. Chen Huajun
* Fix misuse of TextDatumGetCString().Tom Lane2015-07-02
| | | | | | | | | | "TextDatumGetCString(PG_GETARG_TEXT_P(x))" is formally wrong: a text* is not a Datum. Although this coding will accidentally fail to fail on all known platforms, it risks leaking memory if a detoast step is needed, unlike "TextDatumGetCString(PG_GETARG_DATUM(x))" which is what's used elsewhere. Make pg_get_object_address() fall in line with other uses. Noted while reviewing two-arg current_setting() patch.
* Add an optional missing_ok argument to SQL function current_setting().Tom Lane2015-07-02
| | | | | | | This allows convenient checking for existence of a GUC from SQL, which is particularly useful when dealing with custom variables. David Christensen, reviewed by Jeevan Chalke
* Remove obsolete heap_formtuple/modifytuple/deformtuple functions.Heikki Linnakangas2015-07-02
| | | | | | | | | | These variants used the old-style 'n'/' ' NULL indicators. The new-style functions have been available since version 8.1. That should be long enough that if there is still any old external code using these functions, they can just switch to the new functions without worrying about backwards compatibility Peter Geoghegan
* Use appendStringInfoString/Char et al where appropriate.Heikki Linnakangas2015-07-02
| | | | | | Patch by David Rowley. Backpatch to 9.5, as some of the calls were new in 9.5, and keeping the code in sync with master makes future backpatching easier.
* Don't leave pg_hba and pg_ident data lying around in running backends.Tom Lane2015-07-01
| | | | | | | | | | | | | | | | Free the contexts holding this data after we're done using it, by the expedient of attaching them to the PostmasterContext which we were already taking care to delete (and where, indeed, this data used to live before commits e5e2fc842c418432 and 7c45e3a3c682f855). This saves a probably-usually-negligible amount of space per running backend. It also avoids leaving potentially-security-sensitive data lying around in memory in processes that don't need it. You'd have to be unusually paranoid to think that that amounts to a live security bug, so I've not gone so far as to forcibly zero the memory; but there surely isn't a good reason to keep this data around. Arguably this is a memory management bug in the aforementioned commits, but it doesn't seem important enough to back-patch.
* Make sampler_random_fract() actually obey its API contract.Tom Lane2015-07-01
| | | | | | | | | | | | This function is documented to return a value in the range (0,1), which is what its predecessor anl_random_fract() did. However, the new version depends on pg_erand48() which returns a value in [0,1). The possibility of returning zero creates hazards of division by zero or trying to compute log(0) at some call sites, and it might well break third-party modules using anl_random_fract() too. So let's change it to never return zero. Spotted by Coverity. Michael Paquier, cosmetically adjusted by me
* Make XLogFileCopy() look the same as in 9.4.Fujii Masao2015-07-01
| | | | | | | | | | | | | | | | XLogFileCopy() was changed heavily in commit de76884. However it was partially reverted in commit 7abc685 and most of those changes to XLogFileCopy() were no longer needed. Then commit 7cbee7c removed those unnecessary code, but XLogFileCopy() looked different in master and 9.4 though the contents are almost the same. This patch makes XLogFileCopy() look the same in master and back-branches, which makes back-patching easier, per discussion on pgsql-hackers. Back-patch to 9.5. Discussion: 55760844.7090703@iki.fi Michael Paquier
* Remove useless check for NULL subexpression.Tom Lane2015-06-30
| | | | | | | Coverity rightly gripes that it's silly to have a test here when the adjacent ExecEvalExpr() would choke on a NULL expression pointer. Petr Jelinek
* Don't call PageGetSpecialPointer() on page until it's been initialized.Heikki Linnakangas2015-06-30
| | | | | | | | | | 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.
* In bttext_abbrev_convert, move pfree to the right place.Robert Haas2015-06-29
| | | | | | | Without this, we might access memory that's already been freed, or leak memory if in the C locale. Peter Geoghegan
* Initialize GIN metapage correctly when replaying metapage-update WAL record.Heikki Linnakangas2015-06-30
| | | | | | | | | | | | | | | | | I broke this with my WAL format refactoring patch. Before that, the metapage was read from disk, and modified in-place regardless of the LSN. That was always a bit silly, as there's no need to read the old page version from disk disk when we're overwriting it anyway. So that was changed in 9.5, but I failed to add a GinInitPage call to initialize the page-headers correctly. Usually you wouldn't notice, because the metapage is already in the page cache and is not zeroed. One way to reproduce this is to perform a VACUUM on an already vacuumed table (so that the vacuum has no real work to do), immediately after a checkpoint, and then perform an immediate shutdown. After recovery, the page headers of the metapage will be incorrectly all-zeroes. Reported by Jeff Janes
* Code + docs review for escaping of option values (commit 11a020eb6).Tom Lane2015-06-29
| | | | | | | | | Avoid memory leak from incorrect choice of how to free a StringInfo (resetStringInfo doesn't do it). Now that pg_split_opts doesn't scribble on the optstr, mark that as "const" for clarity. Attach the commentary in protocol.sgml to the right place, and add documentation about the user-visible effects of this change on postgres' -o option and libpq's PGOPTIONS option.
* Translation updatesPeter Eisentraut2015-06-28
| | | | | Source-Git-URL: git://git.postgresql.org/git/pgtranslation/messages.git Source-Git-Hash: fb7e72f46cfafa1b5bfe4564d9686d63a1e6383f
* Run the C portions of guc-file.l through pgindent.Tom Lane2015-06-28
| | | | | Yeah, I know, pretty anal-retentive of me. But we oughta find some way to automate this for the .y and .l files.
* Improve design and implementation of pg_file_settings view.Tom Lane2015-06-28
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | As first committed, this view reported on the file contents as they were at the last SIGHUP event. That's not as useful as reporting on the current contents, and what's more, it didn't work right on Windows unless the current session had serviced at least one SIGHUP. Therefore, arrange to re-read the files when pg_show_all_settings() is called. This requires only minor refactoring so that we can pass changeVal = false to set_config_option() so that it won't actually apply any changes locally. In addition, add error reporting so that errors that would prevent the configuration files from being loaded, or would prevent individual settings from being applied, are visible directly in the view. This makes the view usable for pre-testing whether edits made in the config files will have the desired effect, before one actually issues a SIGHUP. I also added an "applied" column so that it's easy to identify entries that are superseded by later entries; this was the main use-case for the original design, but it seemed unnecessarily hard to use for that. Also 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. However, since the original coding of the pg_file_settings view depended on such suppression *not* happening, we couldn't have fixed this issue now without first doing something with pg_file_settings. Now we suppress duplicates by marking them "ignored" within ProcessConfigFileInternal, which doesn't hide them in the view.) Lesser changes include: Drive the view directly off the ConfigVariable list, instead of making a basically-equivalent second copy of the data. There's no longer any need to hang onto the data permanently, anyway. Convert show_all_file_settings() to do its work in one call and return a tuplestore; this avoids risks associated with assuming that the GUC state will hold still over the course of query execution. (I think there were probably latent bugs here, though you might need something like a cursor on the view to expose them.) Arrange to run SIGHUP processing in a short-lived memory context, to forestall process-lifespan memory leaks. (There is one known leak in this code, in ProcessConfigDirectory; it seems minor enough to not be worth back-patching a specific fix for.) Remove mistaken assignment to ConfigFileLineno that caused line counting after an include_dir directive to be completely wrong. Add missed failure check in AlterSystemSetConfigFile(). We don't really expect ParseConfigFp() to fail, but that's not an excuse for not checking.
* Also trigger restartpoints based on max_wal_size on standby.Heikki Linnakangas2015-06-29
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | When archive recovery and restartpoints were initially introduced, checkpoint_segments was ignored on the grounds that the files restored from archive don't consume any space in the recovery server. That was changed in later releases, but even then it was arguably a feature rather than a bug, as performing restartpoints as often as checkpoints during normal operation might be excessive, but you might nevertheless not want to waste a lot of space for pre-allocated WAL by setting checkpoint_segments to a high value. But now that we have separate min_wal_size and max_wal_size settings, you can bound WAL usage with max_wal_size, and still avoid consuming excessive space usage by setting min_wal_size to a lower value, so that argument is moot. There are still some issues with actually limiting the space usage to max_wal_size: restartpoints in recovery can only start after seeing the checkpoint record, while a checkpoint starts flushing buffers as soon as the redo-pointer is set. Restartpoint is paced to happen at the same leisurily speed, determined by checkpoint_completion_target, as checkpoints, but because they are started later, max_wal_size can be exceeded by upto one checkpoint cycle's worth of WAL, depending on checkpoint_completion_target. But that seems better than not trying at all, and max_wal_size is a soft limit anyway. The documentation already claimed that max_wal_size is obeyed in recovery, so this just fixes the behaviour to match the docs. However, add some weasel-words there to mention that max_wal_size may well be exceeded by some amount in recovery.
* Promote the assertion that XLogBeginInsert() is not called twice into ERROR.Heikki Linnakangas2015-06-28
| | | | | | | | | Seems like cheap insurance for WAL bugs. A spurious call to XLogBeginInsert() in itself would be fairly harmless, but if there is any data registered and the insertion is not completed/cancelled properly, there is a risk that the data ends up in a wrong WAL record. Per Jeff Janes's suggestion.
* Fix double-XLogBeginInsert call in GIN page splits.Heikki Linnakangas2015-06-28
| | | | | | | | | | | | | | If data checksums or wal_log_hints is on, and a GIN page is split, the code to find a new, empty, block was called after having already called XLogBeginInsert(). That causes an assertion failure or PANIC, if finding the new block involves updating a FSM page that had not been modified since last checkpoint, because that update is WAL-logged, which calls XLogBeginInsert again. Nested XLogBeginInsert calls are not supported. To fix, rearrange GIN code so that XLogBeginInsert is called later, after finding the victim buffers. Reported by Jeff Janes.
* Add missing_ok option to the SQL functions for reading files.Heikki Linnakangas2015-06-28
| | | | | | | | | | | | | | | This makes it possible to use the functions without getting errors, if there is a chance that the file might be removed or renamed concurrently. pg_rewind needs to do just that, although this could be useful for other purposes too. (The changes to pg_rewind to use these functions will come in a separate commit.) The read_binary_file() function isn't very well-suited for extensions.c's purposes anymore, if it ever was. So bite the bullet and make a copy of it in extension.c, tailored for that use case. This seems better than the accidental code reuse, even if it's a some more lines of code. Michael Paquier, with plenty of kibitzing by me.
* Fix comment for GetCurrentIntegerTimestamp().Kevin Grittner2015-06-28
| | | | | | The unit of measure is microseconds, not milliseconds. Backpatch to 9.3 where the function and its comment were added.
* Avoid passing NULL to memcmp() in lookups of zero-argument functions.Tom Lane2015-06-27
| | | | | | | | | | | | | | | | | | | | A few places assumed they could pass NULL for the argtypes array when looking up functions known to have zero arguments. At first glance it seems that this should be safe enough, since memcmp() is surely not allowed to fetch any bytes if its count argument is zero. However, close reading of the C standard says that such calls have undefined behavior, so we'd probably best avoid it. Since the number of places doing this is quite small, and some other places looking up zero-argument functions were already passing dummy arrays, let's standardize on the latter solution rather than hacking the function lookup code to avoid calling memcmp() in these cases. I also added Asserts to catch any future violations of the new rule. Given the utter lack of any evidence that this actually causes any problems in the field, I don't feel a need to back-patch this change. Per report from Piotr Stefaniak, though this is not his patch.
* Fix typo in commentHeikki Linnakangas2015-06-27
| | | | Etsuro Fujita
* Avoid hot standby cancels from VAC FREEZESimon Riggs2015-06-27
| | | | | | | | | | | | 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
* Fix DDL command collection for TRANSFORMAlvaro Herrera2015-06-26
| | | | | | | | Commit b488c580ae, which added the DDL command collection feature, neglected to update the code that commit cac76582053e had previously added two weeks earlier for the TRANSFORM feature. Reported by Michael Paquier.
* Fix BRIN xlog replayAlvaro Herrera2015-06-26
| | | | | | | | There was a confusion about which block number to use when storing an item's pointer in the revmap -- the revmap page's blkno was being used, not the data page's blkno. Spotted-by: Jeff Janes
* Be more conservative about removing tablespace "symlinks".Robert Haas2015-06-26
| | | | | | | | | | Don't apply rmtree(), which will gleefully remove an entire subtree, and don't even apply unlink() unless it's symlink or a directory, the only things that we expect to find. Amit Kapila, with minor tweaks by me, per extensive discussions involving Andrew Dunstan, Fujii Masao, and Heikki Linnakangas, at least some of whom also reviewed the code.
* Don't warn about creating temporary or unlogged hash indexes.Robert Haas2015-06-26
| | | | | | | Warning people that no WAL-logging will be done doesn't make sense in this case. Michael Paquier
* Reduce log level for background worker events from LOG to DEBUG1.Robert Haas2015-06-26
| | | | | | | Per discussion, LOG is just too chatty for something that will happen as routinely as this. Pavel Stehule
* Fix the fallback memory barrier implementation to be reentrant.Andres Freund2015-06-26
| | | | | | | | | | | | | | | | | | | | | | | | | | | This was essentially "broken" since 0c8eda62; but until more recently (14e8803f) barriers usage in signal handlers was infrequent. The failure to be reentrant was noticed because the test_shm_mq, which uses memory barriers at a high frequency, occasionally got stuck on some solaris buildfarm animals. Turns out, those machines use sun studio 12.1, which doesn't yet have efficient memory barrier support. A machine with a newer sun studio did not fail. Forcing the barrier fallback to be used on x86 allows to reproduce the problem. The new fallback is to use kill(PostmasterPid, 0) based on the theory that that'll always imply a barrier due to checking the liveliness of PostmasterPid on systems old enough to need fallback support. It's hard to come up with a good and performant fallback. I'm not backpatching this for now - the problem isn't active in the back branches, and we haven't backpatched barrier changes for now. Additionally master looks entirely different than the back branches due to the new atomics abstraction. It seems better to let this rest in master, where the non-reentrancy actively causes a problem, and then consider backpatching. Found-By: Robert Haas Discussion: 55626265.3060800@dunslane.net