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* Ignore recovery_min_apply_delay until recovery has reached consistent stateFujii Masao2016-03-06
| | | | | | | | | | | | | | | | | | | Previously recovery_min_apply_delay was applied even before recovery had reached consistency. This could cause us to wait a long time unexpectedly for read-only connections to be allowed. It's problematic because the standby was useless during that wait time. This patch changes recovery_min_apply_delay so that it's applied once the database has reached the consistent state. That is, even if the delay is set, the standby tries to replay WAL records as fast as possible until it has reached consistency. Author: Michael Paquier Reviewed-By: Julien Rouhaud Reported-By: Greg Clough Backpatch: 9.4, where recovery_min_apply_delay was added Bug: #13770 Discussion: http://www.postgresql.org/message-id/20151111155006.2644.84564@wrigleys.postgresql.org
* Minor improvements to transaction manager README.Robert Haas2016-03-04
| | | | | | | | A simple SELECT is handled by PortalRunSelect, not ProcessQuery. Also, the previous indentation was unclear: change it so that a deeper level of indentation indicates that the outer function calls the inner one. Stas Kelvich
* Minor optimizations based on ParallelContext having nworkers_launched.Robert Haas2016-03-04
| | | | | | | | | | | Originally, we didn't have nworkers_launched, so code that used parallel contexts had to be preprared for the possibility that not all of the workers requested actually got launched. But now we can count on knowing the number of workers that were successfully launched, which can shave off a few cycles and simplify some code slightly. Amit Kapila, reviewed by Haribabu Kommi, per a suggestion from Peter Geoghegan.
* Revert buggy optimization of index scansSimon Riggs2016-03-03
| | | | | | | 606c0123d627 attempted to reduce cost of index scans using > and < strategies, though got that completely wrong in a few complex cases. Revert whole patch until we find a safe optimization.
* Change the format of the VM fork to add a second bit per page.Robert Haas2016-03-01
| | | | | | | | | | | | | | | | | | | | | | | The new bit indicates whether every tuple on the page is already frozen. It is cleared only when the all-visible bit is cleared, and it can be set only when we vacuum a page and find that every tuple on that page is both visible to every transaction and in no need of any future vacuuming. A future commit will use this new bit to optimize away full-table scans that would otherwise be triggered by XID wraparound considerations. A page which is merely all-visible must still be scanned in that case, but a page which is all-frozen need not be. This commit does not attempt that optimization, although that optimization is the goal here. It seems better to get the basic infrastructure in place first. Per discussion, it's very desirable for pg_upgrade to automatically migrate existing VM forks from the old format to the new format. That, too, will be handled in a follow-on patch. Masahiko Sawada, reviewed by Kyotaro Horiguchi, Fujii Masao, Amit Kapila, Simon Riggs, Andres Freund, and others, and substantially revised by me.
* Correct StartupSUBTRANS for page wraparoundSimon Riggs2016-02-19
| | | | | | | | | | StartupSUBTRANS() incorrectly handled cases near the max pageid in the subtrans data structure, which in some cases could lead to errors in startup for Hot Standby. This patch wraps the pageids correctly, avoiding any such errors. Identified by exhaustive crash testing by Jeff Janes. Jeff Janes
* Allow the WAL writer to flush WAL at a reduced rate.Andres Freund2016-02-16
| | | | | | | | | | | | | | | | | | | | | | | | Commit 4de82f7d7 increased the WAL flush rate, mainly to increase the likelihood that hint bits can be set quickly. More quickly set hint bits can reduce contention around the clog et al. But unfortunately the increased flush rate can have a significant negative performance impact, I have measured up to a factor of ~4. The reason for this slowdown is that if there are independent writes to the underlying devices, for example because shared buffers is a lot smaller than the hot data set, or because a checkpoint is ongoing, the fdatasync() calls force cache flushes to be emitted to the storage. This is achieved by flushing WAL only if the last flush was longer than wal_writer_delay ago, or if more than wal_writer_flush_after (new GUC) unflushed blocks are pending. Based on some tests the default for wal_writer_delay is 1MB, which seems to work well both on SSD and rotational media. To avoid negative performance impact due to 4de82f7d7 an earlier commit (db76b1e) made SetHintBits() more likely to succeed; preventing performance regressions in the pgbench tests I performed. Discussion: 20160118163908.GW10941@awork2.anarazel.de
* Change delimiter used for display of NextXIDJoe Conway2016-02-12
| | | | | | | | | | | | | NextXID has been rendered in the form of a pg_lsn even though it really is not. This can cause confusion, so change the format from %u/%u to %u:%u, per discussion on hackers. Complaint by me, patch by me and Bruce, reviewed by Michael Paquier and Alvaro. Applied to HEAD only. Author: Joe Conway, Bruce Momjian Reviewed-by: Michael Paquier, Alvaro Herrera Backpatch-through: master
* Make builtin lwlock tranche names consistent.Robert Haas2016-02-12
| | | | | | Previously, we had a mix of styles. Amit Kapila
* Shift the responsibility for emitting "database system is shut down".Tom Lane2016-02-11
| | | | | | | | | | | | | | | | | | Historically this message has been emitted at the end of ShutdownXLOG(). That's not an insane place for it in a standalone backend, but in the postmaster environment we've grown a fair amount of stuff that happens later, including archiver/walsender shutdown, stats collector shutdown, etc. Recent buildfarm experimentation showed that on slower machines there could be many seconds' delay between finishing ShutdownXLOG() and actual postmaster exit. That's fairly confusing, both for testing purposes and for DBAs. Hence, move the code that prints this message into UnlinkLockFiles(), so that it comes out just after we remove the postmaster's pidfile. That is a more appropriate definition of "is shut down" from the point of view of "pg_ctl stop", for example. In general, removing the pidfile should be the last externally-visible action of either a postmaster or a standalone backend; compare commit d73d14c271653dff10c349738df79ea03b85236c for instance. So this seems like a reasonably future-proof approach.
* Revert "Temporarily make pg_ctl and server shutdown a whole lot chattier."Tom Lane2016-02-10
| | | | | | This reverts commit 3971f64843b02e4a55d854156bd53e46a0588e45 and a couple of followon debugging commits; I think we've learned what we can from them.
* Add more chattiness in server shutdown.Tom Lane2016-02-09
| | | | | | | Early returns from the buildfarm show that there's a bit of a gap in the logging I added in 3971f64843b02e4a: the portion of CreateCheckPoint() after CheckPointGuts() can take a fair amount of time. Add a few more log messages in that section of code. This too shall be reverted later.
* Temporarily make pg_ctl and server shutdown a whole lot chattier.Tom Lane2016-02-08
| | | | | | | | | | | | | This is a quick hack, due to be reverted when its purpose has been served, to try to gather information about why some of the buildfarm critters regularly fail with "postmaster does not shut down" complaints. Maybe they are just really overloaded, but maybe something else is going on. Hence, instrument pg_ctl to print the current time when it starts waiting for postmaster shutdown and when it gives up, and add a lot of logging of the current time in the server's checkpoint and shutdown code paths. No attempt has been made to make this pretty. I'm not even totally sure if it will build on Windows, but we'll soon find out.
* Introduce a new GUC force_parallel_mode for testing purposes.Robert Haas2016-02-07
| | | | | | | | | | | | | | | When force_parallel_mode = true, we enable the parallel mode restrictions for all queries for which this is believed to be safe. For the subset of those queries believed to be safe to run entirely within a worker, we spin up a worker and run the query there instead of running it in the original process. When force_parallel_mode = regress, make additional changes to allow the regression tests to run cleanly even though parallel workers have been injected under the hood. Taken together, this facilitates both better user testing and better regression testing of the parallelism code. Robert Haas, with help from Amit Kapila and Rushabh Lathia.
* Introduce group locking to prevent parallel processes from deadlocking.Robert Haas2016-02-07
| | | | | | | | | | | | | For locking purposes, we now regard heavyweight locks as mutually non-conflicting between cooperating parallel processes. There are some possible pitfalls to this approach that are not to be taken lightly, but it works OK for now and can be changed later if we find a better approach. Without this, it's very easy for parallel queries to silently self-deadlock if the user backend holds strong relation locks. Robert Haas, with help from Amit Kapila. Thanks to Noah Misch and Andres Freund for extensive discussion of possible issues with this approach.
* Fix lossy KNN GiST when ordering operator returns non-float8 value.Teodor Sigaev2016-02-02
| | | | | | | | | | | | | | | | | KNN GiST with recheck flag should return to executor the same type as ordering operator, GiST detects this type by looking to return type of function which implements ordering operator. But occasionally detecting code works after replacing ordering operator function to distance support function. Distance support function always returns float8, so, detecting code get float8 instead of actual return type of ordering operator. Built-in opclasses don't have ordering operator which doesn't return non-float8 value, so, tests are impossible here, at least now. Backpatch to 9.5 where lozzy KNN was introduced. Author: Alexander Korotkov Report by: Artur Zakirov
* Make all built-in lwlock tranche IDs fixed.Robert Haas2016-02-02
| | | | | | | This makes the values more stable, which seems like a good thing for anybody who needs to look at at them. Alexander Korotkov and Amit Kapila
* Fix misspelled function name in comment.Heikki Linnakangas2016-02-01
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* Fix whitespacePeter Eisentraut2016-01-30
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* Add gin_clean_pending_list function to clean up GIN pending listFujii Masao2016-01-28
| | | | | | | | | | | | | | | | This function cleans up the pending list of the GIN index by moving entries in it to the main GIN data structure in bulk. It returns the number of pages cleaned up from the pending list. This function is useful, for example, when the pending list needs to be cleaned up *quickly* to improve the performance of the search using GIN index. VACUUM can do the same thing, too, but it may take days to run on a large table. Jeff Janes, reviewed by Julien Rouhaud, Jaime Casanova, Alvaro Herrera and me. Discussion: CAMkU=1x8zFkpfnozXyt40zmR3Ub_kHu58LtRmwHUKRgQss7=iQ@mail.gmail.com
* Improve ResourceOwners' behavior for large numbers of owned objects.Tom Lane2016-01-26
| | | | | | | | | | | | | | | | | | The original coding was quite fast so long as objects were always released in reverse order of addition; otherwise, it degenerated into O(N^2) behavior due to searching for the array element to delete. Improve matters by switching to hashed storage when the number of objects of a given type exceeds 64. (The cutover point is open to discussion, of course, but some simple performance testing suggests that hashing has enough overhead to be a loser below there.) Also, refactor resowner.c so that we don't need N copies of the array management code. Since all the resource IDs the code currently needs to deal with are either pointers or integers, it seems sufficient to create a one-size-fits-all infrastructure in which everything is converted to a Datum for storage. Aleksander Alekseev, reviewed by Stas Kelvich, further fixes by me
* Suppress compiler warning.Tom Lane2016-01-21
| | | | | | | | Given the limited range of i, these shifts should not cause any problem, but that apparently doesn't stop some compilers from whining about them. David Rowley
* Improve index AMs' opclass validation procedures.Tom Lane2016-01-21
| | | | | | | | | | | | | | | | | | | | The amvalidate functions added in commit 65c5fcd353a859da were on the crude side. Improve them in a few ways: * Perform signature checking for operators and support functions. * Apply more thorough checks for missing operators and functions, where possible. * Instead of reporting problems as ERRORs, report most problems as INFO messages and make the amvalidate function return FALSE. This allows more than one problem to be discovered per run. * Report object names rather than OIDs, and work a bit harder on making the messages understandable. Also, remove a few more opr_sanity regression test queries that are now superseded by the amvalidate checks.
* Remove unused argument from ginInsertCleanup()Fujii Masao2016-01-22
| | | | It's an oversight in commit dc943ad.
* Refactor headers to split out standby defsSimon Riggs2016-01-20
| | | | Jeff Janes
* Speedup 2PC by skipping two phase state files in normal pathSimon Riggs2016-01-20
| | | | | | | | | | | | | | | | | 2PC state info is written only to WAL at PREPARE, then read back from WAL at COMMIT PREPARED/ABORT PREPARED. Prepared transactions that live past one bufmgr checkpoint cycle will be written to disk in the same form as previously. Crash recovery path is not altered. Measured performance gains of 50-100% for short 2PC transactions by completely avoiding writing files and fsyncing. Other optimizations still available, further patches in related areas expected. Stas Kelvich and heavily edited by Simon Riggs Based upon earlier ideas and patches by Michael Paquier and Heikki Linnakangas, a concrete example of how Postgres-XC has fed back ideas into PostgreSQL. Reviewed by Michael Paquier, Jeff Janes and Andres Freund Performance testing by Jesper Pedersen
* Refactor to create generic WAL page read callbackSimon Riggs2016-01-20
| | | | | | | | | | Previously we didn’t have a generic WAL page read callback function, surprisingly. Logical decoding has logical_read_local_xlog_page(), which was actually generic, so move that to xlogfunc.c and rename to read_local_xlog_page(). Maintain logical_read_local_xlog_page() so existing callers still work. As requested by Michael Paquier, Alvaro Herrera and Andres Freund
* Fix assorted inconsistencies in GiST opclass support function declarations.Tom Lane2016-01-19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The conventions specified by the GiST SGML documentation were widely ignored. For example, the strategy-number argument for "consistent" and "distance" functions is specified to be a smallint, but most of the built-in support functions declared it as an integer, and for that matter the core code passed it using Int32GetDatum not Int16GetDatum. None of that makes any real difference at runtime, but it's quite confusing for newcomers to the code, and it makes it very hard to write an amvalidate() function that checks support function signatures. So let's try to instill some consistency here. Another similar issue is that the "query" argument is not of a single well-defined type, but could have different types depending on the strategy (corresponding to search operators with different righthand-side argument types). Some of the functions threw up their hands and declared the query argument as being of "internal" type, which surely isn't right ("any" would have been more appropriate); but the majority position seemed to be to declare it as being of the indexed data type, corresponding to a search operator with both input types the same. So I've specified a convention that that's what to do always. Also, the result of the "union" support function actually must be of the index's storage type, but the documentation suggested declaring it to return "internal", and some of the functions followed that. Standardize on telling the truth, instead. Similarly, standardize on declaring the "same" function's inputs as being of the storage type, not "internal". Also, somebody had forgotten to add the "recheck" argument to both the documentation of the "distance" support function and all of their SQL declarations, even though the C code was happily using that argument. Clean that up too. Fix up some other omissions in the docs too, such as documenting that union's second input argument is vestigial. So far as the errors in core function declarations go, we can just fix pg_proc.h and bump catversion. Adjusting the erroneous declarations in contrib modules is more debatable: in principle any change in those scripts should involve an extension version bump, which is a pain. However, since these changes are purely cosmetic and make no functional difference, I think we can get away without doing that.
* Restructure index access method API to hide most of it at the C level.Tom Lane2016-01-17
| | | | | | | | | | | | | | | | | | | | | | | | This patch reduces pg_am to just two columns, a name and a handler function. All the data formerly obtained from pg_am is now provided in a C struct returned by the handler function. This is similar to the designs we've adopted for FDWs and tablesample methods. There are multiple advantages. For one, the index AM's support functions are now simple C functions, making them faster to call and much less error-prone, since the C compiler can now check function signatures. For another, this will make it far more practical to define index access methods in installable extensions. A disadvantage is that SQL-level code can no longer see attributes of index AMs; in particular, some of the crosschecks in the opr_sanity regression test are no longer possible from SQL. We've addressed that by adding a facility for the index AM to perform such checks instead. (Much more could be done in that line, but for now we're content if the amvalidate functions more or less replace what opr_sanity used to do.) We might also want to expose some sort of reporting functionality, but this patch doesn't do that. Alexander Korotkov, reviewed by Petr Jelínek, and rather heavily editorialized on by me.
* Add new user fn pg_current_xlog_flush_location()Simon Riggs2016-01-12
| | | | | Tomas Vondra, reviewed by Michael Paquier and Amit Kapila Minor edits by me
* Maintain local LogwrtResult consistentlySimon Riggs2016-01-12
| | | | | Teach GetFlushRecPtr() to update LogwrtResult cache as performed by all other functions in xlog.c
* Revoke change to rmgr desc of btree vacuumSimon Riggs2016-01-09
| | | | Per discussion with Andres Freund
* Avoid pin scan for replay of XLOG_BTREE_VACUUMSimon Riggs2016-01-09
| | | | | | | | | | | | | | | | | | | | Replay of XLOG_BTREE_VACUUM during Hot Standby was previously thought to require complex interlocking that matched the requirements on the master. This required an O(N) operation that became a significant problem with large indexes, causing replication delays of seconds or in some cases minutes while the XLOG_BTREE_VACUUM was replayed. This commit skips the “pin scan” that was previously required, by observing in detail when and how it is safe to do so, with full documentation. The pin scan is skipped only in replay; the VACUUM code path on master is not touched here. The current commit still performs the pin scan for toast indexes, though this can also be avoided if we recheck scans on toast indexes. Later patch will address this. No tests included. Manual tests using an additional patch to view WAL records and their timing have shown the change in WAL records and their handling has successfully reduced replication delay.
* Fix overly-strict assertions in spgtextproc.c.Tom Lane2016-01-02
| | | | | | | | | | | | | | | | | spg_text_inner_consistent is capable of reconstructing an empty string to pass down to the next index level; this happens if we have an empty string coming in, no prefix, and a dummy node label. (In practice, what is needed to trigger that is insertion of a whole bunch of empty-string values.) Then, we will arrive at the next level with in->level == 0 and a non-NULL (but zero length) in->reconstructedValue, which is valid but the Assert tests weren't expecting it. Per report from Andreas Seltenreich. This has no impact in non-Assert builds, so should not be a problem in production, but back-patch to all affected branches anyway. In passing, remove a couple of useless variable initializations and shorten the code by not duplicating DatumGetPointer() calls.
* Update copyright for 2016Bruce Momjian2016-01-02
| | | | Backpatch certain files through 9.1
* Fix comments about WAL rule "write xlog before data" versus pg_multixact.Noah Misch2016-01-01
| | | | | | | | | | | Recovery does not achieve its goal of zeroing all pg_multixact entries whose accompanying WAL records never reached disk. Remove that claim and justify its expendability. Detail the need for TrimMultiXact(), which has little in common with the TrimCLOG() rationale. Merge two tightly-related comments. Stop presenting pg_multixact as specific to heap_lock_tuple(); PostgreSQL 9.3 extended its use to heap_update(). Noticed while investigating a report from Andres Freund.
* Rename (new|old)estCommitTs to (new|old)estCommitTsXidJoe Conway2015-12-28
| | | | | | | | | | | | | The variables newestCommitTs and oldestCommitTs sound as if they are timestamps, but in fact they are the transaction Ids that correspond to the newest and oldest timestamps rather than the actual timestamps. Rename these variables to reflect that they are actually xids: to wit newestCommitTsXid and oldestCommitTsXid respectively. Also modify related code in a similar fashion, particularly the user facing output emitted by pg_controldata and pg_resetxlog. Complaint and patch by me, review by Tom Lane and Alvaro Herrera. Backpatch to 9.5 where these variables were first introduced.
* Fix brin_summarize_new_values() to check index type and ownership.Tom Lane2015-12-26
| | | | | | | | | | brin_summarize_new_values() did not check that the passed OID was for an index at all, much less that it was a BRIN index, and would fail in obscure ways if it wasn't (possibly damaging data first?). It also lacked any permissions test; by analogy to VACUUM, we should only allow the table's owner to summarize. Noted by Jeff Janes, fix by Michael Paquier and me
* Fix typo in comment.Robert Haas2015-12-18
| | | | Amit Langote
* Provide a way to predefine LWLock tranche IDs.Robert Haas2015-12-15
| | | | | | | | | | | It's a bit cumbersome to use LWLockNewTrancheId(), because the returned value needs to be shared between backends so that each backend can call LWLockRegisterTranche() with the correct ID. So, for built-in tranches, use a hard-coded value instead. This is motivated by an upcoming patch adding further built-in tranches. Andres Freund and Robert Haas
* Fix bug in SetOffsetVacuumLimit() triggered by find_multixact_start() failure.Andres Freund2015-12-14
| | | | | | | | | | | | | | | | Previously, if find_multixact_start() failed, SetOffsetVacuumLimit() would install 0 into MultiXactState->offsetStopLimit if it previously succeeded. Luckily, there are no known cases where find_multixact_start() will return an error in 9.5 and above. But if it were to happen, for example due to filesystem permission issues, it'd be somewhat bad: GetNewMultiXactId() could continue allocating mxids even if close to a wraparound, or it could erroneously stop allocating mxids, even if no wraparound is looming. The wrong value would be corrected the next time SetOffsetVacuumLimit() is called, or by a restart. Reported-By: Noah Misch, although this is not his preferred fix Discussion: 20151210140450.GA22278@alap3.anarazel.de Backpatch: 9.5, where the bug was introduced as part of 4f627f
* Fix commit timestamp initializationAlvaro Herrera2015-12-11
| | | | | | | | | | | | | | | | | | | | | | This module needs explicit initialization in order to replay WAL records in recovery, but we had broken this recently following changes to make other (stranger) scenarios work correctly. To fix, rework the initialization sequence so that it always takes place before WAL replay commences for both master and standby. I could have gone for a more localized fix that just added a "startup" call for the master server, but it seemed better to restructure the existing callers as well so that the whole thing made more sense. As a drawback, there is more control logic in xlog.c now than previously, but doing otherwise meant passing down the ControlFile flag, which seemed uglier as a whole. This also meant adding a check to not re-execute ActivateCommitTs if it had already been called. Reported by Fujii Masao. Backpatch to 9.5.
* Improve some messagesPeter Eisentraut2015-12-10
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* Fix bug leading to restoring unlogged relations from empty files.Andres Freund2015-12-10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | At the end of crash recovery, unlogged relations are reset to the empty state, using their init fork as the template. The init fork is copied to the main fork without going through shared buffers. Unfortunately WAL replay so far has not necessarily flushed writes from shared buffers to disk at that point. In normal crash recovery, and before the introduction of 'fast promotions' in fd4ced523 / 9.3, the END_OF_RECOVERY checkpoint flushes the buffers out in time. But with fast promotions that's not the case anymore. To fix, force WAL writes targeting the init fork to be flushed immediately (using the new FlushOneBuffer() function). In 9.5+ that flush can centrally be triggered from the code dealing with restoring full page writes (XLogReadBufferForRedoExtended), in earlier releases that responsibility is in the hands of XLOG_HEAP_NEWPAGE's replay function. Backpatch to 9.1, even if this currently is only known to trigger in 9.3+. Flushing earlier is more robust, and it is advantageous to keep the branches similar. Typical symptoms of this bug are errors like 'ERROR: index "..." contains unexpected zero page at block 0' shortly after promoting a node. Reported-By: Thom Brown Author: Andres Freund and Michael Paquier Discussion: 20150326175024.GJ451@alap3.anarazel.de Backpatch: 9.1-
* Further tweak commit_timestamp behaviorAlvaro Herrera2015-12-03
| | | | | | | | | | | | | | | | | | | | | | As pointed out by Fujii Masao, we weren't quite there on a standby behaving sanely: first because we were failing to acquire the correct state in the case where no XLOG_PARAMETER_CHANGE message was sent (because a checkpoint had already happened after the setting was changed in the master, and then the standby was restarted); and second because promoting the standby with the feature enabled failed to activate it if the master had the feature disabled. This patch fixes both those misbehaviors hopefully without re-introducing any old problems. Also change the hint emitted in a standby together with the error message about the feature being disabled, to make it point out that the place to chance the setting is the master. Otherwise, if the setting is already enabled in the standby, it is very confusing to have it say that the setting must be enabled ... Authors: Álvaro Herrera, Petr Jelínek. Backpatch to 9.5.
* Fix typo in comment.Robert Haas2015-11-19
| | | | Amit Langote
* Remove function names from some elog() calls in heapam.c.Andres Freund2015-11-19
| | | | | | | | | | At least one of the names was, due to a function renaming late in the development of ON CONFLICT, wrong. Since including function names in error messages is against the message style guide anyway, remove them from the messages. Discussion: CAM3SWZT8paz=usgMVHm0XOETkQvzjRtAUthATnmaHQQY0obnGw@mail.gmail.com Backpatch: 9.5, where ON CONFLICT was introduced
* Message improvementsPeter Eisentraut2015-11-16
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* Move each SLRU's lwlocks to a separate tranche.Robert Haas2015-11-12
| | | | | | | | | | This makes it significantly easier to identify these lwlocks in LWLOCK_STATS or Trace_lwlocks output. It's also arguably better from a modularity standpoint, since lwlock.c no longer needs to know anything about the LWLock needs of the higher-level SLRU facility. Ildus Kurbangaliev, reviewd by Álvaro Herrera and by me.
* Pass extra data to bgworkers, and use this to fix parallel contexts.Robert Haas2015-11-05
| | | | | | | | | | | | | | | | | | | | | | | | Up until now, the total amount of data that could be passed to a background worker at startup was one datum, which can be a small as 4 bytes on some systems. That's enough to pass a dsm_handle or an array index, but not much else. Add a bgw_extra flag to the BackgroundWorker struct, allowing up to 128 bytes to be passed to a new worker on any platform. Use this to fix a problem I recently discovered with the parallel context machinery added in 9.5: the master assigns each worker an array index, and each worker subsequently assigns itself an array index, and there's nothing to guarantee that the two sets of indexes match, leading to chaos. Normally, I would not back-patch the change to add bgw_extra, since it is basically a feature addition. However, since 9.5 is still in beta and there seems to be no other sensible way to repair the broken parallel context machinery, back-patch to 9.5. Existing background worker code can ignore the bgw_extra field without a problem, but might need to be recompiled since the structure size has changed. Report and patch by me. Review by Amit Kapila.
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