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* Rename log_lock_failure GUC to log_lock_failures for consistency.Fujii Masao11 days
| | | | | | | | | | | This commit renames the GUC log_lock_failure to log_lock_failures to align with the existing similar setting log_lock_waits, which uses the plural form. This improves naming consistency across related GUCs. Suggested-by: Peter Eisentraut <peter@eisentraut.org> Author: Fujii Masao <masao.fujii@gmail.com Reviewed-by: Peter Eisentraut <peter@eisentraut.org> Discussion: https://postgr.es/m/7a8198b6-d5b8-4910-b41e-8d3efcbb015d@eisentraut.org
* Make XactLockTableWait() and ConditionalXactLockTableWait() interruptable more.Fujii Masao2025-05-31
| | | | | | | | | | | | | | | | | | | | | | | | | | Previously, XactLockTableWait() and ConditionalXactLockTableWait() could enter a non-interruptible loop when they successfully acquired a lock on a transaction but the transaction still appeared to be running. Since this loop continued until the transaction completed, it could result in long, uninterruptible waits. Although this scenario is generally unlikely since XactLockTableWait() and ConditionalXactLockTableWait() can basically acquire a transaction lock only when the transaction is not running, it can occur in a hot standby. In such cases, the transaction may still appear active due to the KnownAssignedXids list, even while no lock on the transaction exists. For example, this situation can happen when creating a logical replication slot on a standby. The cause of the non-interruptible loop was the absence of CHECK_FOR_INTERRUPTS() within it. This commit adds CHECK_FOR_INTERRUPTS() to the loop in both functions, ensuring they can be interrupted safely. Back-patch to all supported branches. Author: Kevin K Biju <kevinkbiju@gmail.com> Reviewed-by: Fujii Masao <masao.fujii@gmail.com> Discussion: https://postgr.es/m/CAM45KeELdjhS-rGuvN=ZLJ_asvZACucZ9LZWVzH7bGcD12DDwg@mail.gmail.com Backpatch-through: 13
* Revert function to get memory context stats for processesDaniel Gustafsson2025-05-23
| | | | | | | | | Due to concerns raised about the approach, and memory leaks found in sensitive contexts the functionality is reverted. This reverts commits 45e7e8ca9, f8c115a6c, d2a1ed172, 55ef7abf8 and 042a66291 for v18 with an intent to revisit this patch for v19. Discussion: https://postgr.es/m/594293.1747708165@sss.pgh.pa.us
* Eliminate divide in new fast-path locking codeDavid Rowley2025-04-27
| | | | | | | | | | | | | | | | | | | | | | | c4d5cb71d2 adjusted the fast-path locking code to allow some configuration of the number of fast-path locking slots via the max_locks_per_transaction GUC. In that commit the FAST_PATH_REL_GROUP() macro used integer division to determine the fast-path locking group slot to use for the lock. The divisor in this case is always a power-of-two value. Here we swap out the divide by a bitwise-AND, which is a significantly faster operation to perform. In passing, adjust the code that's setting FastPathLockGroupsPerBackend so that it's more clear that the value being set is a power-of-two. Also, adjust some comments in the area which contained some magic numbers. It seems better to justify the 1024 upper limit in the location where the #define is made instead of where it is used. Author: David Rowley <drowleyml@gmail.com> Reviewed-by: Tomas Vondra <tomas@vondra.me> Discussion: https://postgr.es/m/CAApHDvodr3bcnpxcs7+k-3cFwYR0tP-BYhyd2PpDhe-bCx9i=g@mail.gmail.com
* Assert lack of hazardous buffer locks before possible catalog read.Noah Misch2025-04-17
| | | | | | | | | | | | | | | | | | | | | Commit 0bada39c83a150079567a6e97b1a25a198f30ea3 fixed a bug of this kind, which existed in all branches for six days before detection. While the probability of reaching the trouble was low, the disruption was extreme. No new backends could start, and service restoration needed an immediate shutdown. Hence, add this to catch the next bug like it. The new check in RelationIdGetRelation() suffices to make autovacuum detect the bug in commit 243e9b40f1b2dd09d6e5bf91ebf6e822a2cd3704 that led to commit 0bada39. This also checks in a number of similar places. It replaces each Assert(IsTransactionState()) that pertained to a conditional catalog read. No back-patch for now, but a back-patch of commit 243e9b4 should back-patch this, too. A back-patch could omit the src/test/regress changes, since back branches won't gain new index columns. Reported-by: Alexander Lakhin <exclusion@gmail.com> Discussion: https://postgr.es/m/20250410191830.0e.nmisch@google.com Discussion: https://postgr.es/m/10ec0bc3-5933-1189-6bb8-5dec4114558e@gmail.com
* Fix recently introduced typosDaniel Gustafsson2025-04-11
| | | | | | | | | This fixes typos in docs and comments introduced during the v18 development cycle, to keep them from ending up in backbranches. Author: Jacob Brazeal <jacob.brazeal@gmail.com> Reviewed-by: Daniel Gustafsson <daniel@yesql.se> Discussion: https://postgr.es/m/CA+COZaCgGua25f2hSrjrDLJcJJAHkwoKgTTqUy-wyL1=64JNjw@mail.gmail.com
* Add function to get memory context stats for processesDaniel Gustafsson2025-04-08
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This adds a function for retrieving memory context statistics and information from backends as well as auxiliary processes. The intended usecase is cluster debugging when under memory pressure or unanticipated memory usage characteristics. When calling the function it sends a signal to the specified process to submit statistics regarding its memory contexts into dynamic shared memory. Each memory context is returned in detail, followed by a cumulative total in case the number of contexts exceed the max allocated amount of shared memory. Each process is limited to use at most 1Mb memory for this. A summary can also be explicitly requested by the user, this will return the TopMemoryContext and a cumulative total of all lower contexts. In order to not block on busy processes the caller specifies the number of seconds during which to retry before timing out. In the case where no statistics are published within the set timeout, the last known statistics are returned, or NULL if no previously published statistics exist. This allows dash- board type queries to continually publish even if the target process is temporarily congested. Context records contain a timestamp to indicate when they were submitted. Author: Rahila Syed <rahilasyed90@gmail.com> Reviewed-by: Daniel Gustafsson <daniel@yesql.se> Reviewed-by: Andres Freund <andres@anarazel.de> Reviewed-by: Tomas Vondra <tomas@vondra.me> Reviewed-by: Atsushi Torikoshi <torikoshia@oss.nttdata.com> Reviewed-by: Fujii Masao <masao.fujii@oss.nttdata.com> Reviewed-by: Alexander Korotkov <aekorotkov@gmail.com> Discussion: https://postgr.es/m/CAH2L28v8mc9HDt8QoSJ8TRmKau_8FM_HKS41NeO9-6ZAkuZKXw@mail.gmail.com
* Improve accounting for PredXactList, RWConflictPool and PGPROCTomas Vondra2025-04-02
| | | | | | | | | | | | | | | | | | | | | | | | Various places allocated shared memory by first allocating a small chunk using ShmemInitStruct(), followed by ShmemAlloc() calls to allocate more memory. Unfortunately, ShmemAlloc() does not update ShmemIndex, so this affected pg_shmem_allocations - it only shown the initial chunk. This commit modifies the following allocations, to allocate everything as a single chunk, and then split it internally. - PredXactList - RWConflictPool - PGPROC structures - Fast-Path Lock Array The fast-path lock array is allocated separately, not as a part of the PGPROC structures allocation. Author: Rahila Syed <rahilasyed90@gmail.com> Reviewed-by: Andres Freund <andres@anarazel.de> Reviewed-by: Nazir Bilal Yavuz <byavuz81@gmail.com> Reviewed-by: Tomas Vondra <tomas@vondra.me> Discussion: https://postgr.es/m/CAH2L28vHzRankszhqz7deXURxKncxfirnuW68zD7+hVAqaS5GQ@mail.gmail.com
* Fix crash if LockErrorCleanup() is called twiceHeikki Linnakangas2025-03-28
| | | | | | | | | | | | | | | The refactoring in commit 3c0fd64fec removed the clearing of awaitedLock from LockErrorCleanup(). It's still needed, otherwise LockErrorCleanup() during abort processing will try to update the LOCALLOCK struct even after the lock has already been released. Put it back. Reported-by: Richard Guo <guofenglinux@gmail.com> Reported-by: Robins Tharakan <tharakan@gmail.com> Reported-by: Alexander Lakhin <exclusion@gmail.com> Discussion: https://www.postgresql.org/message-id/flat/CAMbWs4_dNX1SzBmvFdoY-LxJh_4W_BjtVd5i008ihfU-wFF=eg@mail.gmail.com Discussion: https://www.postgresql.org/message-id/18832-38e5575b1bbd7277@postgresql.org Discussion: https://www.postgresql.org/message-id/e11a30e5-c0d8-491d-8546-3a1b50c10ad4@gmail.com
* aio: Add io_method=io_uringAndres Freund2025-03-26
| | | | | | | | | | | | | | | | | | | | | | Performing AIO using io_uring can be considerably faster than io_method=worker, particularly when lots of small IOs are issued, as a) the context-switch overhead for worker based AIO becomes more significant b) the number of IO workers can become limiting io_uring, however, is linux specific and requires an additional compile-time dependency (liburing). This implementation is fairly simple and there are substantial optimization opportunities. The description of the existing AIO_IO_COMPLETION wait event is updated to make the difference between it and the new AIO_IO_URING_EXECUTION clearer. Reviewed-by: Noah Misch <noah@leadboat.com> Reviewed-by: Jakub Wartak <jakub.wartak@enterprisedb.com> Discussion: https://postgr.es/m/uvrtrknj4kdytuboidbhwclo4gxhswwcpgadptsjvjqcluzmah%40brqs62irg4dt Discussion: https://postgr.es/m/20210223100344.llw5an2aklengrmn@alap3.anarazel.de Discussion: https://postgr.es/m/stj36ea6yyhoxtqkhpieia2z4krnam7qyetc57rfezgk4zgapf@gcnactj4z56m
* Add GUC option to log lock acquisition failures.Fujii Masao2025-03-14
| | | | | | | | | | | | | | | | | | | | | | This commit introduces a new GUC, log_lock_failure, which controls whether a detailed log message is produced when a lock acquisition fails. Currently, it only supports logging lock failures caused by SELECT ... NOWAIT. The log message includes information about all processes holding or waiting for the lock that couldn't be acquired, helping users analyze and diagnose the causes of lock failures. Currently, this option does not log failures from SELECT ... SKIP LOCKED, as that could generate excessive log messages if many locks are skipped, causing unnecessary noise. This mechanism can be extended in the future to support for logging lock failures from other commands, such as LOCK TABLE ... NOWAIT. Author: Yuki Seino <seinoyu@oss.nttdata.com> Co-authored-by: Fujii Masao <masao.fujii@gmail.com> Reviewed-by: Jelte Fennema-Nio <postgres@jeltef.nl> Discussion: https://postgr.es/m/411280a186cc26ef7034e0f2dfe54131@oss.nttdata.com
* Optimize iteration over PGPROC for fast-path lock searches.Fujii Masao2025-03-14
| | | | | | | | | | | | | | | | | | | | | | This commit improves efficiency in FastPathTransferRelationLocks() and GetLockConflicts(), which iterate over PGPROCs to search for fast-path locks. Previously, these functions recalculated the fast-path group during every loop iteration, even though it remained constant. This update optimizes the process by calculating the group once and reusing it throughout the loop. The functions also now skip empty fast-path groups, avoiding unnecessary scans of their slots. Additionally, groups belonging to inactive backends (with pid=0) are always empty, so checking the group is sufficient to bypass these backends, further enhancing performance. Author: Fujii Masao <masao.fujii@gmail.com> Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi> Reviewed-by: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com> Discussion: https://postgr.es/m/07d5fd6a-71f1-4ce8-8602-4cc6883f4bd1@oss.nttdata.com
* Make lwlocknames.h generated file less uglyÁlvaro Herrera2025-03-13
| | | | | | | | | | We can make the output look a bit better by aligning each lock's definition, so add some padding space to achieve that. This change makes no practical difference, but casual onlookers will be less distracted by (lack of) whitespace. Author: Gurjeet Singh <gurjeet@singh.im> Discussion: https://postgr.es/m/CABwTF4VxfwDtRV-H22_XK4XeDogaV-Vaobu+af5U=8ZAZn9ZZQ@mail.gmail.com
* Make parallel nbtree index scans use an LWLock.Peter Geoghegan2025-03-08
| | | | | | | | | | | | | | Teach parallel nbtree index scans to use an LWLock (not a spinlock) to protect the scan's shared descriptor state. Preparation for an upcoming patch that will add skip scan optimizations to nbtree. That patch will create the need to occasionally allocate memory while the scan descriptor is locked, while copying datums that were serialized by another backend. Author: Peter Geoghegan <pg@bowt.ie> Reviewed-By: Matthias van de Meent <boekewurm+postgres@gmail.com> Discussion: https://postgr.es/m/CAH2-Wz=PKR6rB7qbx+Vnd7eqeB5VTcrW=iJvAsTsKbdG+kW_UA@mail.gmail.com
* Make FP_LOCK_SLOTS_PER_BACKEND look like a functionTomas Vondra2025-03-04
| | | | | | | | | | | | | The FP_LOCK_SLOTS_PER_BACKEND macro looks like a constant, but it depends on the max_locks_per_transaction GUC, and thus can change. This is non-obvious and confusing, so make it look more like a function by renaming it to FastPathLockSlotsPerBackend(). While at it, use the macro when initializing fast-path shared memory, instead of using the formula. Reported-by: Andres Freund Discussion: https://postgr.es/m/ffiwtzc6vedo6wb4gbwelon5nefqg675t5c7an2ta7pcz646cg%40qwmkdb3l4ett
* Add static asserts for MAX_BACKENDS limiting factorsAndres Freund2025-02-24
| | | | | | | So far the various dependencies were documented in the comment above MAX_BACKENDS, but not checked. Discussion: https://postgr.es/m/CA+COZaBO_s3LfALq=b+HcBHFSOEGiApVjrRacCe4VP9m7CJsNQ@mail.gmail.com
* Base LWLock limits directly on MAX_BACKENDSAndres Freund2025-02-24
| | | | | | | | | | | | | | | | | | | Jacob reported that comments for LW_SHARED_MASK referenced a MAX_BACKENDS limit of 2^23-1, but that MAX_BACKENDS is actually limited to 2^18-1. The limit was lowered in 48354581a49c, but the comment in lwlock.c wasn't updated. Instead of just fixing the comment, it seems better to directly base the lwlock defines on MAX_BACKENDS and add static assertions to ensure that there is enough space. That way there's no comment that can go out of sync in the future. As part of that change I noticed that for some reason the high bit wasn't used for flags, which seems somewhat odd. Redefine the flag values to start at the highest bit. Reported-by: Jacob Brazeal <jacob.brazeal@gmail.com> Reviewed-by: Jacob Brazeal <jacob.brazeal@gmail.com> Discussion: https://postgr.es/m/CA+COZaBO_s3LfALq=b+HcBHFSOEGiApVjrRacCe4VP9m7CJsNQ@mail.gmail.com
* Move MAX_BACKENDS to procnumber.hAndres Freund2025-02-24
| | | | | | | | | | | | | MAX_BACKENDS influences many things besides postmaster. I e.g. noticed that we don't have static assertions ensuring BUF_REFCOUNT_MASK is big enough for MAX_BACKENDS, adding them would require including postmaster.h in buf_internals.h which doesn't seem right. While at that, add MAX_BACKENDS_BITS, as that's useful in various places for static assertions (to be added in subsequent commits). Reviewed-by: Thomas Munro <thomas.munro@gmail.com> Discussion: https://postgr.es/m/wptizm4qt6yikgm2pt52xzyv6ycmqiutloyvypvmagn7xvqkce@d4xuv3mylpg4
* Allow lwlocks to be disownedAndres Freund2025-02-21
| | | | | | | | | | | | | | | | | | To implement AIO writes, the backend initiating writes needs to transfer the lock ownership to the AIO subsystem, so the lock held during the write can be released in another backend. Other backends need to be able to "complete" an asynchronously started IO to avoid deadlocks (consider e.g. one backend starting IO for a buffer and then waiting for a heavyweight lock held by another relation followed by the current holder of the heavyweight lock waiting for the IO to complete). To that end, this commit adds LWLockDisown() and LWLockReleaseDisowned(). If code uses LWLockDisown() it's the code's responsibility to ensure that the lock is released in case of errors. Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi> Discussion: https://postgr.es/m/1f6b50a7-38ef-4d87-8246-786d39f46ab9@iki.fi
* Fix grammatical typos around possessive "its"John Naylor2025-01-29
| | | | | | | | Some places spelled it "it's", which is short for "it is". In passing, fix a couple other nearby grammatical errors. Author: Jacob Brazeal <jacob.brazeal@gmail.com> Discussion: https://postgr.es/m/CA+COZaAO8g1KJCV0T48=CkJMjAnnfTGLWOATz+2aCh40c2Nm+g@mail.gmail.com
* Allow changing autovacuum_max_workers without restarting.Nathan Bossart2025-01-06
| | | | | | | | | | | | | | | | | | | | | | | This commit introduces a new parameter named autovacuum_worker_slots that controls how many autovacuum worker slots to reserve during server startup. Modifying this new parameter's value does require a server restart, but it should typically be set to the upper bound of what you might realistically need to set autovacuum_max_workers. With that new parameter in place, autovacuum_max_workers can now be changed with a SIGHUP (e.g., pg_ctl reload). If autovacuum_max_workers is set higher than autovacuum_worker_slots, a WARNING is emitted, and the server will only start up to autovacuum_worker_slots workers at a given time. If autovacuum_max_workers is set to a value less than the number of currently-running autovacuum workers, the existing workers will continue running, but no new workers will be started until the number of running autovacuum workers drops below autovacuum_max_workers. Reviewed-by: Sami Imseih, Justin Pryzby, Robert Haas, Andres Freund, Yogesh Sharma Discussion: https://postgr.es/m/20240410212344.GA1824549%40nathanxps13
* Fix an assortment of spelling mistakes and typosDavid Rowley2025-01-02
| | | | | Author: Alexander Lakhin <exclusion@gmail.com> Discussion: https://postgr.es/m/5812a0b9-b0cf-4151-9a14-d9f00e4f2858@gmail.com
* Update copyright for 2025Bruce Momjian2025-01-01
| | | | Backpatch-through: 13
* Replace PGPROC.isBackgroundWorker with isRegularBackend.Tom Lane2024-12-28
| | | | | | | | | Commit 34486b609 effectively redefined isBackgroundWorker as meaning "not a regular backend", whereas before it had the narrower meaning of AmBackgroundWorkerProcess(). For clarity, rename the field to isRegularBackend and invert its sense. Discussion: https://postgr.es/m/1808397.1735156190@sss.pgh.pa.us
* Exclude parallel workers from connection privilege/limit checks.Tom Lane2024-12-28
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Cause parallel workers to not check datallowconn, rolcanlogin, and ACL_CONNECT privileges. The leader already checked these things (except for rolcanlogin which might have been checked for a different role). Re-checking can accomplish little except to induce unexpected failures in applications that might not even be aware that their query has been parallelized. We already had the principle that parallel workers rely on their leader to pass a valid set of authorization information, so this change just extends that a bit further. Also, modify the ReservedConnections, datconnlimit and rolconnlimit logic so that these limits are only enforced against regular backends, and only regular backends are counted while checking if the limits were already reached. Previously, background processes that had an assigned database or role were subject to these limits (with rather random exclusions for autovac workers and walsenders), and the set of existing processes that counted against each limit was quite haphazard as well. The point of these limits, AFAICS, is to ensure the availability of PGPROC slots for regular backends. Since all other types of processes have their own separate pools of PGPROC slots, it makes no sense either to enforce these limits against them or to count them while enforcing the limit. While edge-case failures of these sorts have been possible for a long time, the problem got a good deal worse with commit 5a2fed911 (CVE-2024-10978), which caused parallel workers to make some of these checks using the leader's current role where before we had used its AuthenticatedUserId, thus allowing parallel queries to fail after SET ROLE. The previous behavior was fairly accidental and I have no desire to return to it. This patch includes reverting 73c9f91a1, which was an emergency hack to suppress these same checks in some cases. It wasn't complete, as shown by a recent bug report from Laurenz Albe. We can also revert fd4d93d26 and 492217301, which hacked around the same problems in one regression test. In passing, remove the special case for autovac workers in CheckMyDatabase; it seems cleaner to have AutoVacWorkerMain pass the INIT_PG_OVERRIDE_ALLOW_CONNS flag, now that that does what's needed. Like 5a2fed911, back-patch to supported branches (which sadly no longer includes v12). Discussion: https://postgr.es/m/1808397.1735156190@sss.pgh.pa.us
* Reserve a PGPROC slot and semaphore for the slotsync worker process.Tom Lane2024-12-28
| | | | | | | | | | | | | | | | | | | | | | | | | The need for this was missed in commit 93db6cbda, with the result being that if we launch a slotsync worker it would consume one of the PGPROCs in the max_connections pool. That could lead to inability to launch the worker, or to subsequent failures of connection requests that should have succeeded according to the configured settings. Rather than create some one-off infrastructure to support this, let's group the slotsync worker with the existing autovac launcher in a new category of "special worker" processes. These are kind of like auxiliary processes, but they cannot use that infrastructure because they need to be able to run transactions. For the moment, make these processes share the PGPROC freelist used for autovac workers (which previously supplied the autovac launcher too). This is partly to avoid an ABI change in v17, and partly because it seems silly to have a freelist with at most two members. This might be worth revisiting if we grow enough workers in this category. Tom Lane and Hou Zhijie. Back-patch to v17. Discussion: https://postgr.es/m/1808397.1735156190@sss.pgh.pa.us
* Remove useless casts to (const void *)Peter Eisentraut2024-12-06
| | | | | Similar to commit 7f798aca1d5, but I didn't think to look for "const" as well.
* Drop "Lock" suffix from LWLock wait event namesÁlvaro Herrera2024-12-03
| | | | | | | | | | | | | Commit da952b415f44 unintentially reverted the SQL-visible part of commit 14a910109126, which breaks queries joining pg_wait_events with pg_stat_acivity. Remove the suffix again. Backpatch to 17. Reported-by: Christophe Courtois <christophe.courtois@dalibo.com> Author: Bertrand Drouvot <bertranddrouvot.pg@gmail.com> Discussion: https://postgr.es/m/18728-450924477056a339%40postgresql.org Discussion: https://postgr.es/m/Z01w1+LihtRiS0Te@ip-10-97-1-34.eu-west-3.compute.internal
* Assign a child slot to every postmaster child processHeikki Linnakangas2024-11-14
| | | | | | | | | | | | | | | | | | | | | | | | | | | Previously, only backends, autovacuum workers, and background workers had an entry in the PMChildFlags array. With this commit, all postmaster child processes, including all the aux processes, have an entry. Dead-end backends still don't get an entry, though, and other processes that don't touch shared memory will never mark their PMChildFlags entry as active. We now maintain separate freelists for different kinds of child processes. That ensures that there are always slots available for autovacuum and background workers. Previously, pre-authentication backends could prevent autovacuum or background workers from starting up, by using up all the slots. The code to manage the slots in the postmaster process is in a new pmchild.c source file. Because postmaster.c is just so large. Assigning pmsignal slot numbers is now pmchild.c's responsibility. This replaces the PMChildInUse array in pmsignal.c. Some of the comments in postmaster.c still talked about the "stats process", but that was removed in commit 5891c7a8ed. Fix those while we're at it. Reviewed-by: Andres Freund <andres@anarazel.de> Discussion: https://www.postgresql.org/message-id/a102f15f-eac4-4ff2-af02-f9ff209ec66f@iki.fi
* Revert pg_wal_replay_wait() stored procedureAlexander Korotkov2024-11-04
| | | | | | | | | | | | | | | | This commit reverts 3c5db1d6b0, and subsequent improvements and fixes including 8036d73ae3, 867d396ccd, 3ac3ec580c, 0868d7ae70, 85b98b8d5a, 2520226c95, 014f9f34d2, e658038772, e1555645d7, 5035172e4a, 6cfebfe88b, 73da6b8d1b, and e546989a26. The reason for reverting is a set of remaining issues. Most notably, the stored procedure appears to need more effort than the utility statement to turn the backend into a "snapshot-less" state. This makes an approach to use stored procedures questionable. Catversion is bumped. Discussion: https://postgr.es/m/Zyhj2anOPRKtb0xW%40paquier.xyz
* Split ProcSleep function into JoinWaitQueue and ProcSleepHeikki Linnakangas2024-11-04
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Split ProcSleep into two functions: JoinWaitQueue and ProcSleep. JoinWaitQueue is called while holding the partition lock, and inserts the current process to the wait queue, while ProcSleep() does the actual sleeping. ProcSleep() is now called without holding the partition lock, and it no longer re-acquires the partition lock before returning. That makes the wakeup a little cheaper. Once upon a time, re-acquiring the partition lock was needed to prevent a signal handler from longjmping out at a bad time, but these days our signal handlers just set flags, and longjmping can only happen at points where we explicitly run CHECK_FOR_INTERRUPTS(). If JoinWaitQueue detects an "early deadlock" before even joining the wait queue, it returns without changing the shared lock entry, leaving the cleanup of the shared lock entry to the caller. This makes the handling of an early deadlock the same as the dontWait=true case. One small user-visible side-effect of this refactoring is that we now only set the 'ps' title to say "waiting" when we actually enter the sleep, not when the lock is skipped because dontWait=true, or when a deadlock is detected early before entering the sleep. This eliminates the 'lockAwaited' global variable in proc.c, which was largely redundant with 'awaitedLock' in lock.c Note: Updating the local lock table is now the caller's responsibility. JoinWaitQueue and ProcSleep are now only responsible for modifying the shared state. Seems a little nicer that way. Based on Thomas Munro's earlier patch and observation that ProcSleep doesn't really need to re-acquire the partition lock. Reviewed-by: Maxim Orlov Discussion: https://www.postgresql.org/message-id/7c2090cd-a72a-4e34-afaa-6dd2ef31440e@iki.fi
* Move TRACE calls into WaitOnLock()Heikki Linnakangas2024-11-04
| | | | | | | | LockAcquire is a long and complex function. Pushing more stuff to its subroutines makes it a little more manageable. Reviewed-by: Maxim Orlov Discussion: https://www.postgresql.org/message-id/7c2090cd-a72a-4e34-afaa-6dd2ef31440e@iki.fi
* Set MyProc->heldLocks in ProcSleepHeikki Linnakangas2024-11-04
| | | | | | | | | | | | Previously, ProcSleep()'s caller was responsible for setting MyProc->heldLocks, and we had comments to remind about that. But it seems simpler to make ProcSleep() itself responsible for it. ProcSleep() already set the other info about the lock its waiting for (waitLock, waitProcLock and waitLockMode), so it is natural for it to set heldLocks too. Reviewed-by: Maxim Orlov Discussion: https://www.postgresql.org/message-id/7c2090cd-a72a-4e34-afaa-6dd2ef31440e@iki.fi
* Fix comment in LockReleaseAll() on when locallock->nLock can be zeroHeikki Linnakangas2024-11-04
| | | | | | | | We reach this case also e.g. when a deadlock is detected, not only when we run out of memory. Reviewed-by: Maxim Orlov Discussion: https://www.postgresql.org/message-id/7c2090cd-a72a-4e34-afaa-6dd2ef31440e@iki.fi
* Use ProcNumbers instead of direct Latch pointers to address other procsHeikki Linnakangas2024-11-01
| | | | | | | | This is in preparation for replacing Latches with a new abstraction. That's still work in progress, but this seems a little tidier anyway, so let's get this refactoring out of the way already. Discussion: https://www.postgresql.org/message-id/391abe21-413e-4d91-a650-b663af49500c%40iki.fi
* Remove unused #include's from backend .c filesPeter Eisentraut2024-10-27
| | | | | | | | as determined by IWYU These are mostly issues that are new since commit dbbca2cf299. Discussion: https://www.postgresql.org/message-id/flat/0df1d5b1-8ca8-4f84-93be-121081bde049%40eisentraut.org
* Refactor GetLockStatusData() to skip backends/groups without fast-path locks.Fujii Masao2024-10-25
| | | | | | | | | | | | | | | | Previously, GetLockStatusData() checked all slots for every backend to gather fast-path lock data, which could be inefficient. This commit refactors it by skipping backends with PID=0 (since they don't hold fast-path locks) and skipping groups with no registered fast-path locks, improving efficiency. This refactoring is particularly beneficial, for example when max_connections and max_locks_per_transaction are set high, as it reduces unnecessary checks across numerous slots. Author: Fujii Masao Reviewed-by: Bertrand Drouvot Discussion: https://postgr.es/m/a0a00c44-31e9-4c67-9846-fb9636213ac9@oss.nttdata.com
* Move LSN waiting declarations and definitions to better placeAlexander Korotkov2024-10-24
| | | | | | | | | | | | | | | | | | | 3c5db1d6b implemented the pg_wal_replay_wait() stored procedure. Due to the patch development history, the implementation resided in src/backend/commands/waitlsn.c (src/include/commands/waitlsn.h for headers). 014f9f34d moved pg_wal_replay_wait() itself to src/backend/access/transam/xlogfuncs.c near to the WAL-manipulation functions. But most of the implementation stayed in place. The code in src/backend/commands/waitlsn.c has nothing to do with commands, but is related to WAL. So, this commit moves this code into src/backend/access/transam/xlogwait.c (src/include/access/xlogwait.h for headers). Reported-by: Peter Eisentraut Discussion: https://postgr.es/m/18c0fa64-0475-415e-a1bd-665d922c5201%40eisentraut.org Reviewed-by: Pavel Borisov
* Fix race condition in committing a serializable transactionHeikki Linnakangas2024-10-21
| | | | | | | | | | | | | | | | The finished transaction list can contain XIDs that are older than the serializable global xmin. It's a short-lived state; ClearOldPredicateLocks() removes any such transactions from the list, and it's called whenever the global xmin advances. But if another backend calls SummarizeOldestCommittedSxact() in that window, it will call SerialAdd() on an XID that's older than the global xmin, or if there are no more transactions running, when global xmin is invalid. That trips the assertion in SerialAdd(). Fixes bug #18658 reported by Andrew Bille. Thanks to Alexander Lakhin for analysis. Backpatch to all versions. Discussion: https://www.postgresql.org/message-id/18658-7dab125ec688c70b%40postgresql.org
* Use an shmem_exit callback to remove backend from PMChildFlags on exitHeikki Linnakangas2024-10-08
| | | | | | | | | | | | This seems nicer than having to duplicate the logic between InitProcess() and ProcKill() for which child processes have a PMChildFlags slot. Move the MarkPostmasterChildActive() call earlier in InitProcess(), out of the section protected by the spinlock. Reviewed-by: Andres Freund <andres@anarazel.de> Discussion: https://www.postgresql.org/message-id/a102f15f-eac4-4ff2-af02-f9ff209ec66f@iki.fi
* Warn if LOCKTAG_TUPLE is held at commit, under debug_assertions.Noah Misch2024-09-24
| | | | | | | | | | | | The current use always releases this locktag. A planned use will continue that intent. It will involve more areas of code, making unlock omissions easier. Warn under debug_assertions, like we do for various resource leaks. Back-patch to v12 (all supported versions), the plan for the commit of the new use. Reviewed by Heikki Linnakangas. Discussion: https://postgr.es/m/20240512232923.aa.nmisch@google.com
* Fix asserts in fast-path locking codeTomas Vondra2024-09-23
| | | | | | | | | | | | | | | | | | | Commit c4d5cb71d229 introduced a couple asserts in the fast-path locking code, upsetting Coverity. The assert in InitProcGlobal() is clearly wrong, as it assigns instead of checking the value. This is harmless, but doesn't check anything. The asserts in FAST_PATH_ macros are written as if for signed values, but the macros are only called for unsigned ones. That makes the check for (val >= 0) useless. Checks written as ((uint32) x < max) work for both signed and unsigned values. Negative values should wrap to values greater than INT32_MAX. Per Coverity, report by Tom Lane. Reported-by: Tom Lane Discussion: https://postgr.es/m/2891628.1727019959@sss.pgh.pa.us
* Increase the number of fast-path lock slotsTomas Vondra2024-09-21
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Replace the fixed-size array of fast-path locks with arrays, sized on startup based on max_locks_per_transaction. This allows using fast-path locking for workloads that need more locks. The fast-path locking introduced in 9.2 allowed each backend to acquire a small number (16) of weak relation locks cheaply. If a backend needs to hold more locks, it has to insert them into the shared lock table. This is considerably more expensive, and may be subject to contention (especially on many-core systems). The limit of 16 fast-path locks was always rather low, because we have to lock all relations - not just tables, but also indexes, views, etc. For planning we need to lock all relations that might be used in the plan, not just those that actually get used in the final plan. So even with rather simple queries and schemas, we often need significantly more than 16 locks. As partitioning gets used more widely, and the number of partitions increases, this limit is trivial to hit. Complex queries may easily use hundreds or even thousands of locks. For workloads doing a lot of I/O this is not noticeable, but for workloads accessing only data in RAM, the access to the shared lock table may be a serious issue. This commit removes the hard-coded limit of the number of fast-path locks. Instead, the size of the fast-path arrays is calculated at startup, and can be set much higher than the original 16-lock limit. The overall fast-path locking protocol remains unchanged. The variable-sized fast-path arrays can no longer be part of PGPROC, but are allocated as a separate chunk of shared memory and then references from the PGPROC entries. The fast-path slots are organized as a 16-way set associative cache. You can imagine it as a hash table of 16-slot "groups". Each relation is mapped to exactly one group using hash(relid), and the group is then processed using linear search, just like the original fast-path cache. With only 16 entries this is cheap, with good locality. Treating this as a simple hash table with open addressing would not be efficient, especially once the hash table gets almost full. The usual remedy is to grow the table, but we can't do that here easily. The access would also be more random, with worse locality. The fast-path arrays are sized using the max_locks_per_transaction GUC. We try to have enough capacity for the number of locks specified in the GUC, using the traditional 2^n formula, with an upper limit of 1024 lock groups (i.e. 16k locks). The default value of max_locks_per_transaction is 64, which means those instances will have 64 fast-path slots. The main purpose of the max_locks_per_transaction GUC is to size the shared lock table. It is often set to the "average" number of locks needed by backends, with some backends using significantly more locks. This should not be a major issue, however. Some backens may have to insert locks into the shared lock table, but there can't be too many of them, limiting the contention. The only solution is to increase the GUC, even if the shared lock table already has sufficient capacity. That is not free, especially in terms of memory usage (the shared lock table entries are fairly large). It should only happen on machines with plenty of memory, though. In the future we may consider a separate GUC for the number of fast-path slots, but let's try without one first. Reviewed-by: Robert Haas, Jakub Wartak Discussion: https://postgr.es/m/510b887e-c0ce-4a0c-a17a-2c6abb8d9a5c@enterprisedb.com
* Fix inconsistent LWLock tranche name "CommitTsSLRU"Michael Paquier2024-09-04
| | | | | | | | | | | | | | | | This term was using an inconsistent casing between the code and the documentation, using "CommitTsSLRU" in wait_event_names.txt and "CommitTSSLRU" in the code. Let's update the term in the code to reflect what's in the documentation, "CommitTs" being more commonly used, so as pg_stat_activity shows the same term as the documentation. Oversight in 53c2a97a9266. Author: Alexander Lakhin Discussion: https://postgr.es/m/f7e514cf-2446-21f1-a5d2-8c089a6e2168@gmail.com Backpatch-through: 17
* Fix typos and grammar in code comments and docsMichael Paquier2024-09-03
| | | | | Author: Alexander Lakhin Discussion: https://postgr.es/m/f7e514cf-2446-21f1-a5d2-8c089a6e2168@gmail.com
* Rename some shared memory initialization routinesHeikki Linnakangas2024-08-29
| | | | | | | | | | | | | | | | To make them follow the usual naming convention where FoobarShmemSize() calculates the amount of shared memory needed by Foobar subsystem, and FoobarShmemInit() performs the initialization. I didn't rename CreateLWLocks() and InitShmmeIndex(), because they are a little special. They need to be called before any of the other ShmemInit() functions, because they set up the shared memory bookkeeping itself. I also didn't rename InitProcGlobal(), because unlike other Shmeminit functions, it's not called by individual backends. Reviewed-by: Andreas Karlsson Discussion: https://www.postgresql.org/message-id/c09694ff-2453-47e5-b26c-32a16cd75ce6@iki.fi
* Refactor lock manager initialization to make it a bit less specialHeikki Linnakangas2024-08-29
| | | | | | | | | | Split the shared and local initialization to separate functions, and follow the common naming conventions. With this, we no longer create the LockMethodLocalHash hash table in the postmaster process, which was always pointless. Reviewed-by: Andreas Karlsson Discussion: https://www.postgresql.org/message-id/c09694ff-2453-47e5-b26c-32a16cd75ce6@iki.fi
* Implement pg_wal_replay_wait() stored procedureAlexander Korotkov2024-08-02
| | | | | | | | | | | | | | | | | | | | | | | | | | pg_wal_replay_wait() is to be used on standby and specifies waiting for the specific WAL location to be replayed. This option is useful when the user makes some data changes on primary and needs a guarantee to see these changes are on standby. The queue of waiters is stored in the shared memory as an LSN-ordered pairing heap, where the waiter with the nearest LSN stays on the top. During the replay of WAL, waiters whose LSNs have already been replayed are deleted from the shared memory pairing heap and woken up by setting their latches. pg_wal_replay_wait() needs to wait without any snapshot held. Otherwise, the snapshot could prevent the replay of WAL records, implying a kind of self-deadlock. This is why it is only possible to implement pg_wal_replay_wait() as a procedure working without an active snapshot, not a function. Catversion is bumped. Discussion: https://postgr.es/m/eb12f9b03851bb2583adab5df9579b4b%40postgrespro.ru Author: Kartyshov Ivan, Alexander Korotkov Reviewed-by: Michael Paquier, Peter Eisentraut, Dilip Kumar, Amit Kapila Reviewed-by: Alexander Lakhin, Bharath Rupireddy, Euler Taveira Reviewed-by: Heikki Linnakangas, Kyotaro Horiguchi
* Remove --disable-spinlocks.Thomas Munro2024-07-30
| | | | | | | | | | A later change will require atomic support, so it wouldn't make sense for a hypothetical new system not to be able to implement spinlocks. Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi> Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> (concept, not the patch) Reviewed-by: Andres Freund <andres@anarazel.de> (concept, not the patch) Discussion: https://postgr.es/m/3351991.1697728588%40sss.pgh.pa.us
* Use more consistently int64 for page numbers in SLRU-related codeMichael Paquier2024-07-23
| | | | | | | | | | | | | | clog.c, async.c and predicate.c included some SLRU page numbers still handled as 4-byte integers, while int64 should be used for this purpose. These holes have been introduced in 4ed8f0913bfd, that has introduced the use of 8-byte integers for SLRU page numbers, still forgot about the code paths updated by this commit. Reported-by: Noah Misch Author: Aleksander Alekseev, Michael Paquier Discussion: https://postgr.es/m/20240626002747.dc.nmisch@google.com Backpatch-through: 17
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