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* docs: improve description of how to handle multiple databasesBruce Momjian2020-08-21
| | | | | | | | | | This is a redesign of the intro to the managing databases chapter. Discussion: https://postgr.es/m/159586122762.680.1361378513036616007@wrigleys.postgresql.org Author: David G. Johnston Backpatch-through: 9.5
* docs: add COMMENT examples for new features, rename rtreeBruce Momjian2020-08-21
| | | | | | | | | | Reported-by: Jürgen Purtz Discussion: https://postgr.es/m/15ec5428-d46a-1725-f38d-44986a977abb@purtz.de Author: Jürgen Purtz Backpatch-through: 11
* Fix handling of CREATE TABLE LIKE with inheritance.Tom Lane2020-08-21
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | If a CREATE TABLE command uses both LIKE and traditional inheritance, Vars in CHECK constraints and expression indexes that are absorbed from a LIKE parent table tended to get mis-numbered, resulting in wrong answers and/or bizarre error messages (though probably not any actual crashes, thanks to validation occurring in the executor). In v12 and up, the same could happen to Vars in GENERATED expressions, even in cases with no LIKE clause but multiple traditional-inheritance parents. The cause of the problem for LIKE is that parse_utilcmd.c supposed it could renumber such Vars correctly during transformCreateStmt(), which it cannot since we have not yet accounted for columns added via inheritance. Fix that by postponing processing of LIKE INCLUDING CONSTRAINTS, DEFAULTS, GENERATED, INDEXES till after we've performed DefineRelation(). The error with GENERATED and multiple inheritance is a simple oversight in MergeAttributes(); it knows it has to renumber Vars in inherited CHECK constraints, but forgot to apply the same processing to inherited GENERATED expressions (a/k/a defaults). Per bug #16272 from Tom Gottfried. The non-GENERATED variants of the issue are ancient, presumably dating right back to the addition of CREATE TABLE LIKE; hence back-patch to all supported branches. Discussion: https://postgr.es/m/16272-6e32da020e9a9381@postgresql.org
* Fix explain regression test failure.Fujii Masao2020-08-22
| | | | | | | | | | | | | | | | Commit 9d701e624f caused the regression test for EXPLAIN to fail on the buildfarm member prion. This happened because of instability of test output, i.e., in text format, whether "Planning:" line is output varies depending on the system state. This commit updated the regression test so that it ignores that "Planning:" line to produce more stable test output and get rid of the test failure. Back-patch to v13. Author: Fujii Masao Discussion: https://postgr.es/m/1803897.1598021621@sss.pgh.pa.us
* Rework EXPLAIN for planner's buffer usage.Fujii Masao2020-08-21
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit ce77abe63c allowed EXPLAIN (BUFFERS) to report the information on buffer usage during planning phase. However three issues were reported regarding this feature. (1) Previously, EXPLAIN option BUFFERS required ANALYZE. So the query had to be actually executed by specifying ANALYZE even when we want to see only the planner's buffer usage. This was inconvenient especially when the query was write one like DELETE. (2) EXPLAIN included the planner's buffer usage in summary information. So SUMMARY option had to be enabled to report that. Also this format was confusing. (3) The output structure for planning information was not consistent between TEXT format and the others. For example, "Planning" tag was output in JSON format, but not in TEXT format. For (1), this commit allows us to perform EXPLAIN (BUFFERS) without ANALYZE to report the planner's buffer usage. For (2), this commit changed EXPLAIN output so that the planner's buffer usage is reported before summary information. For (3), this commit made the output structure for planning information more consistent between the formats. Back-patch to v13 where the planner's buffer usage was allowed to be reported in EXPLAIN. Reported-by: Pierre Giraud, David Rowley Author: Fujii Masao Reviewed-by: David Rowley, Julien Rouhaud, Pierre Giraud Discussion: https://postgr.es/m/07b226e6-fa49-687f-b110-b7c37572f69e@dalibo.com
* Fix typos in comments.Fujii Masao2020-08-21
| | | | | | Author: Masahiko Sawada Reviewed-by: Fujii Masao Discussion: https://postgr.es/m/CA+fd4k4m9hFSrRLB3etPWO5_v5=MujVZWRtz63q+55hM0Dz25Q@mail.gmail.com
* Fix a few typos in JIT comments and READMEDavid Rowley2020-08-21
| | | | | | | Reviewed-by: Abhijit Menon-Sen Reviewed-by: Andres Freund Discussion: https://postgr.es/m/CAApHDvobgmCs6CohqhKTUf7D8vffoZXQTCBTERo9gbOeZmvLTw%40mail.gmail.com Backpatch-through: 11, where JIT was added
* Revert "Make vacuum a bit more verbose to debug BF failure."Andres Freund2020-08-20
| | | | | | | | | | | This reverts commit 49967da65aec970fcda123acc681f1df5d70bfc6. Enough time has passed that we can be confident that 07f32fcd23a resolved the issue. Therefore we can remove the temporary debugging aids. Author: Andres Freund <andres@anarazel.de> Discussion: https://postgr.es/m/E1k7tGP-0005V0-5k@gemulon.postgresql.org
* Revise REINDEX CONCURRENTLY recovery instructionsAlvaro Herrera2020-08-20
| | | | | | | | | | | | When the leftover invalid index is "ccold", there's no need to re-run the command. Reword the instructions to make that explicit. Backpatch to 12, where REINDEX CONCURRENTLY appeared. Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Reviewed-by: Michael Paquier <michael@paquier.xyz> Reviewed-by: Julien Rouhaud <rjuju123@gmail.com> Discussion: https://postgr.es/m/20200819211312.GA15497@alvherre.pgsql
* Acquire ProcArrayLock exclusively in ProcArrayClearTransaction.Andres Freund2020-08-19
| | | | | | | | | | | | | | | This corrects an oversight by me in 20729324078, which made ProcArrayClearTransaction() increment xactCompletionCount. That requires an exclusive lock, obviously. There's other approaches that avoid the exclusive acquisition, but given that a 2PC commit is fairly heavyweight, it doesn't seem worth doing so. I've not been able to measure a performance difference, unsurprisingly. I did add a comment documenting that we could do so, should it ever become a bottleneck. Reported-By: Tom Lane <tgl@sss.pgh.pa.us> Author: Andres Freund <andres@anarazel.de> Discussion: https://postgr.es/m/1355915.1597794204@sss.pgh.pa.us
* Suppress unnecessary RelabelType nodes in yet more cases.Tom Lane2020-08-19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit a477bfc1d fixed eval_const_expressions() to ensure that it didn't generate unnecessary RelabelType nodes, but I failed to notice that some other places in the planner had the same issue. Really noplace in the planner should be using plain makeRelabelType(), for fear of generating expressions that should be equal() to semantically equivalent trees, but aren't. An example is that because canonicalize_ec_expression() failed to be careful about this, we could end up with an equivalence class containing both a plain Const, and a Const-with-RelabelType representing exactly the same value. So far as I can tell this led to no visible misbehavior, but we did waste a bunch of cycles generating and evaluating "Const = Const-with-RelabelType" to prove such entries are redundant. Hence, move the support function added by a477bfc1d to where it can be more generally useful, and use it in the places where planner code previously used makeRelabelType. Back-patch to v12, like the previous patch. While I have no concrete evidence of any real misbehavior here, it's certainly possible that I overlooked a case where equivalent expressions that aren't equal() could cause a user-visible problem. In any case carrying extra RelabelType nodes through planning to execution isn't very desirable. Discussion: https://postgr.es/m/1311836.1597781384@sss.pgh.pa.us
* Add pg_backend_memory_contexts system view.Fujii Masao2020-08-19
| | | | | | | | | | | | | | | | | | | This view displays the usages of all the memory contexts of the server process attached to the current session. This information is useful to investigate the cause of backend-local memory bloat. This information can be also collected by calling MemoryContextStats(TopMemoryContext) via a debugger. But this technique cannot be uesd in some environments because no debugger is available there. And it outputs lots of text messages and it's not easy to analyze them. So, pg_backend_memory_contexts view allows us to access to backend-local memory contexts information more easily. Bump catalog version. Author: Atsushi Torikoshi, Fujii Masao Reviewed-by: Tatsuhito Kasahara, Andres Freund, Daniel Gustafsson, Robert Haas, Michael Paquier Discussion: https://postgr.es/m/72a656e0f71d0860161e0b3f67e4d771@oss.nttdata.com
* Fix race condition in snapshot caching when 2PC is used.Andres Freund2020-08-18
| | | | | | | | | | | | | | | | | | | | When preparing a transaction xactCompletionCount needs to be incremented, even though the transaction has not committed yet. Otherwise the snapshot used within the transaction otherwise can get reused outside of the prepared transaction. As GetSnapshotData() does not include the current xid when building a snapshot, reuse would not be correct. Somewhat surprisingly the regression tests only rarely show incorrect results without the fix. The reason for that is that often the snapshot's xmax will be >= the backend xid, yielding a snapshot that is correct, despite the bug. I'm working on a reliable test for the bug, but it seems worth seeing whether this fixes all the BF failures while I do. Author: Andres Freund <andres@anarazel.de> Discussion: https://postgr.es/m/E1k7tGP-0005V0-5k@gemulon.postgresql.org
* Avoid non-constant format string argument to fprintf().Heikki Linnakangas2020-08-18
| | | | | | | | | As Tom Lane pointed out, it could defeat the compiler's printf() format string verification. Backpatch to v12, like that patch that introduced it. Discussion: https://www.postgresql.org/message-id/1069283.1597672779%40sss.pgh.pa.us
* snapshot scalability: cache snapshots using a xact completion counter.Andres Freund2020-08-17
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | Previous commits made it faster/more scalable to compute snapshots. But not building a snapshot is still faster. Now that GetSnapshotData() does not maintain RecentGlobal* anymore, that is actually not too hard: This commit introduces xactCompletionCount, which tracks the number of top-level transactions with xids (i.e. which may have modified the database) that completed in some form since the start of the server. We can avoid rebuilding the snapshot's contents whenever the current xactCompletionCount is the same as it was when the snapshot was originally built. Currently this check happens while holding ProcArrayLock. While it's likely possible to perform the check without acquiring ProcArrayLock, it seems better to do that separately / later, some careful analysis is required. Even with the lock this is a significant win on its own. On a smaller two socket machine this gains another ~1.03x, on a larger machine the effect is roughly double (earlier patch version tested though). If we were able to safely avoid the lock there'd be another significant gain on top of that. Author: Andres Freund <andres@anarazel.de> Reviewed-By: Robert Haas <robertmhaas@gmail.com> Reviewed-By: Thomas Munro <thomas.munro@gmail.com> Reviewed-By: David Rowley <dgrowleyml@gmail.com> Discussion: https://postgr.es/m/20200301083601.ews6hz5dduc3w2se@alap3.anarazel.de
* Fix use-after-release issue in PL/SampleMichael Paquier2020-08-18
| | | | | Introduced in adbe62d0. Per buildfarm member prion, when using RELCACHE_FORCE_RELEASE.
* Add PL/Sample to src/test/modules/Michael Paquier2020-08-18
| | | | | | | | | | | | | | | | | PL/Sample is an example template of procedural-language handler. This can be used as a base to implement a custom PL, or as a facility to test APIs dedicated to PLs. Much more could be done in this module, like adding a simple validator, but this is left as future work. The documentation included originally some C code to understand the basics of PL handler implementation, but it was outdated, and not really helpful either if trying to implement a new procedural language, particularly when it came to the integration of a PL installation with CREATE EXTENSION. Author: Mark Wong Reviewed-by: Tom Lane, Michael Paquier Discussion: https://postgr.es/m/20200612172648.GA3327@2ndQuadrant.com
* Disable autovacuum for BRIN test tableAlvaro Herrera2020-08-17
| | | | | | | | This should improve stability in the tests. Per buildfarm member hyrax (CLOBBER_CACHE_ALWAYS) via Tom Lane. Discussion: https://postgr.es/m/871534.1597503261@sss.pgh.pa.us
* Doc: fix description of UNION/CASE/etc type unification.Tom Lane2020-08-17
| | | | | | | | | The description of what select_common_type() does was not terribly accurate. Improve it. David Johnston and Tom Lane Discussion: https://postgr.es/m/1019930.1597613200@sss.pgh.pa.us
* Mark commit and abort WAL records with XLR_SPECIAL_REL_UPDATE.Heikki Linnakangas2020-08-17
| | | | | | | | | | | | | | | | If a commit or abort record includes "dropped relfilenodes", then replaying the record will remove data files. That is surely a "special rel update", but the records were not marked as such. Fix that, teach pg_rewind to expect and ignore them, and add a test case to cover it. It's always been like this, but no backporting for fear of breaking existing applications. If an application parsed the WAL but was not handling commit/abort records, it would stop working. That might be a good thing if it really needed to handle the dropped rels, but it will be caught when the application is updated to work with PostgreSQL v14 anyway. Discussion: https://www.postgresql.org/message-id/07b33e2c-46a6-86a1-5f9e-a7da73fddb95%40iki.fi Reviewed-by: Amit Kapila, Michael Paquier
* Make xact.h usable in frontend.Heikki Linnakangas2020-08-17
| | | | | | | | xact.h included utils/datetime.h, which cannot be used in the frontend (it includes fmgr.h, which needs Datum). But xact.h only needs the definition of TimestampTz from it, which is available directly in datatypes/timestamp.h. Change xact.h to include that instead of utils/datetime.h, so that it can be used in client programs.
* Fix printing last progress report line in client programs.Heikki Linnakangas2020-08-17
| | | | | | | | | | | | | | | | | A number of client programs have a "--progress" option that when printing to a TTY, updates the current line by printing a '\r' and overwriting it. After the last line, '\n' needs to be printed to move the cursor to the next line. pg_basebackup and pgbench got this right, but pg_rewind and pg_checksums were slightly wrong. pg_rewind printed the newline to stdout instead of stderr, and pg_checksums printed the newline even when not printing to a TTY. Fix them, and also add a 'finished' argument to pg_basebackup's progress_report() function, to keep it consistent with the other programs. Backpatch to v12. pg_rewind's newline was broken with the logging changes in commit cc8d415117 in v12, and pg_checksums was introduced in v12. Discussion: https://www.postgresql.org/message-id/82b539e5-ae33-34b0-1aee-22b3379fd3eb@iki.fi
* doc: Fix description about bgwriter and checkpoint in HA sectionMichael Paquier2020-08-17
| | | | | | | | | Since 806a2ae, the work of the bgwriter is split the checkpointer, but a portion of the documentation did not get the message. Author: Masahiko Sawada Discussion: https://postgr.es/m/CA+fd4k6jXxjAtjMVC=wG3=QGpauZBtcgN3Jhw+oV7zXGKVLKzQ@mail.gmail.com Backpatch-through: 9.5
* Fix use of wrong index in ComputeXidHorizons().Andres Freund2020-08-16
| | | | | | | | | | | | | | | | This bug, recently introduced in 941697c3c1a, at least lead to vacuum failing because it found tuples inserted by a running transaction, but below the freeze limit. The freeze limit in turn is directly affected by the aforementioned bug. Thanks to Tom Lane figuring how to make the bug reproducible. We should add a few more assertions to make sure this type of bug isn't as hard to notice, but it's not yet clear how to best do so. Co-Diagnosed-By: Tom Lane <tgl@sss.pgh.pa.us> Author: Andres Freund <andres@anarazel.de> Discussion: https://postgr.es/m/1013484.1597609043@sss.pgh.pa.us
* Make vacuum a bit more verbose to debug BF failure.Andres Freund2020-08-16
| | | | | | | This is temporary. While possibly some more error checking / debugging in this path would be a good thing, it'll not look exactly like this. Discussion: https://postgr.es/m/20200816181604.l54m6kss5ntd6xow@alap3.anarazel.de
* Correct several behavior descriptions in comments.Noah Misch2020-08-15
| | | | | | | | | Reuse cautionary language from src/test/ssl/README in src/test/kerberos/README. SLRUs have had access to six-character segments names since commit 73c986adde5d73a5e2555da9b5c8facedb146dcd, and recovery stopped calling HeapTupleHeaderAdvanceLatestRemovedXid() in commit 558a9165e081d1936573e5a7d576f5febd7fb55a. The other corrections are more self-evident.
* Doc: various improvements for pg_basebackup reference page.Tom Lane2020-08-15
| | | | | | | | | | | | | | | | | Put the -r option in the right section (it certainly isn't an option controlling "the location and format of the output"). Clarify the behavior of the tablespace and waldir options (that part per gripe from robert@interactive.co.uk). Make a large number of small copy-editing fixes in text that visibly wasn't written by native speakers, and try to avoid grammatical inconsistencies between the descriptions of the different options. Back-patch to v13, since HEAD hasn't meaningfully diverged yet. Discussion: https://postgr.es/m/159749418850.14322.216503677134569752@wrigleys.postgresql.org
* Prevent concurrent SimpleLruTruncate() for any given SLRU.Noah Misch2020-08-15
| | | | | | | | | | | | | | | | | The SimpleLruTruncate() header comment states the new coding rule. To achieve this, add locktype "frozenid" and two LWLocks. This closes a rare opportunity for data loss, which manifested as "apparent wraparound" or "could not access status of transaction" errors. Data loss is more likely in pg_multixact, due to released branches' thin margin between multiStopLimit and multiWrapLimit. If a user's physical replication primary logged ": apparent wraparound" messages, the user should rebuild standbys of that primary regardless of symptoms. At less risk is a cluster having emitted "not accepting commands" errors or "must be vacuumed" warnings at some point. One can test a cluster for this data loss by running VACUUM FREEZE in every database. Back-patch to 9.5 (all supported versions). Discussion: https://postgr.es/m/20190218073103.GA1434723@rfd.leadboat.com
* Remove no-longer-usable hstore--1.0--1.1.sql update script.Tom Lane2020-08-15
| | | | | | | | | Since commit 865f14a2d made "=>" unusable as an operator name, it's been impossible either to install hstore 1.0 or to execute this update script. There's not much point in continuing to ship it. Discussion: https://postgr.es/m/653936.1597431032@sss.pgh.pa.us
* Remove obsolete cygwin.h hackPeter Eisentraut2020-08-15
| | | | | | | The version being checked for is 20 years old. Reviewed-by: Marco Atzeri <marco.atzeri@gmail.com> Discussion: https://www.postgresql.org/message-id/flat/aa266ede-baaa-f4e6-06cf-5b1737610e9a%402ndquadrant.com
* Remove obsolete HAVE_BUGGY_SOLARIS_STRTODPeter Eisentraut2020-08-15
| | | | | | | Fixed more than 10 years ago. Reviewed-by: Noah Misch <noah@leadboat.com> Discussion: https://www.postgresql.org/message-id/flat/aa266ede-baaa-f4e6-06cf-5b1737610e9a%402ndquadrant.com
* Mark a few logical decoding related variables with PGDLLIMPORT.Amit Kapila2020-08-15
| | | | | | | | | | Commit 7259736a6e added two variables CheckXidAlive and bsysscan to detect concurrent aborts and used these in inline functions that are part of the API that can be used by extensions. So it is better to mark them with PGDLLIMPORT. Reported-by: Thomas Munro Discussion: https://postgr.es/m/CA+hUKGJ7+HYupd=Pz9+QrXa-C_YnbC4rAYu8V+=OKg=UgdzMeg@mail.gmail.com
* Be more careful about the shape of hashable subplan clauses.Tom Lane2020-08-14
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | nodeSubplan.c expects that the testexpr for a hashable ANY SubPlan has the form of one or more OpExprs whose LHS is an expression of the outer query's, while the RHS is an expression over Params representing output columns of the subquery. However, the planner only went as far as verifying that the clauses were all binary OpExprs. This works 99.99% of the time, because the clauses have the right shape when emitted by the parser --- but it's possible for function inlining to break that, as reported by PegoraroF10. To fix, teach the planner to check that the LHS and RHS contain the right things, or more accurately don't contain the wrong things. Given that this has been broken for years without anyone noticing, it seems sufficient to just give up hashing when it happens, rather than go to the trouble of commuting the clauses back again (which wouldn't necessarily work anyway). While poking at that, I also noticed that nodeSubplan.c had a baked-in assumption that the number of hash clauses is identical to the number of subquery output columns. Again, that's fine as far as parser output goes, but it's not hard to break it via function inlining. There seems little reason for that assumption though --- AFAICS, the only thing it's buying us is not having to store the number of hash clauses explicitly. Adding code to the planner to reject such cases would take more code than getting nodeSubplan.c to cope, so I fixed it that way. This has been broken for as long as we've had hashable SubPlans, so back-patch to all supported branches. Discussion: https://postgr.es/m/1549209182255-0.post@n3.nabble.com
* snapshot scalability: Move subxact info to ProcGlobal, remove PGXACT.Andres Freund2020-08-14
| | | | | | | | | | | | | | | | | | | | Similar to the previous changes this increases the chance that data frequently needed by GetSnapshotData() stays in l2 cache. In many workloads subtransactions are very rare, and this makes the check for that considerably cheaper. As this removes the last member of PGXACT, there is no need to keep it around anymore. On a larger 2 socket machine this and the two preceding commits result in a ~1.07x performance increase in read-only pgbench. For read-heavy mixed r/w workloads without row level contention, I see about 1.1x. Author: Andres Freund <andres@anarazel.de> Reviewed-By: Robert Haas <robertmhaas@gmail.com> Reviewed-By: Thomas Munro <thomas.munro@gmail.com> Reviewed-By: David Rowley <dgrowleyml@gmail.com> Discussion: https://postgr.es/m/20200301083601.ews6hz5dduc3w2se@alap3.anarazel.de
* snapshot scalability: Move PGXACT->vacuumFlags to ProcGlobal->vacuumFlags.Andres Freund2020-08-14
| | | | | | | | | | | | | Similar to the previous commit this increases the chance that data frequently needed by GetSnapshotData() stays in l2 cache. As we now take care to not unnecessarily write to ProcGlobal->vacuumFlags, there should be very few modifications to the ProcGlobal->vacuumFlags array. Author: Andres Freund <andres@anarazel.de> Reviewed-By: Robert Haas <robertmhaas@gmail.com> Reviewed-By: Thomas Munro <thomas.munro@gmail.com> Reviewed-By: David Rowley <dgrowleyml@gmail.com> Discussion: https://postgr.es/m/20200301083601.ews6hz5dduc3w2se@alap3.anarazel.de
* snapshot scalability: Introduce dense array of in-progress xids.Andres Freund2020-08-14
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The new array contains the xids for all connected backends / in-use PGPROC entries in a dense manner (in contrast to the PGPROC/PGXACT arrays which can have unused entries interspersed). This improves performance because GetSnapshotData() always needs to scan the xids of all live procarray entries and now there's no need to go through the procArray->pgprocnos indirection anymore. As the set of running top-level xids changes rarely, compared to the number of snapshots taken, this substantially increases the likelihood of most data required for a snapshot being in l2 cache. In read-mostly workloads scanning the xids[] array will sufficient to build a snapshot, as most backends will not have an xid assigned. To keep the xid array dense ProcArrayRemove() needs to move entries behind the to-be-removed proc's one further up in the array. Obviously moving array entries cannot happen while a backend sets it xid. I.e. locking needs to prevent that array entries are moved while a backend modifies its xid. To avoid locking ProcArrayLock in GetNewTransactionId() - a fairly hot spot already - ProcArrayAdd() / ProcArrayRemove() now needs to hold XidGenLock in addition to ProcArrayLock. Adding / Removing a procarray entry is not a very frequent operation, even taking 2PC into account. Due to the above, the dense array entries can only be read or modified while holding ProcArrayLock and/or XidGenLock. This prevents a concurrent ProcArrayRemove() from shifting the dense array while it is accessed concurrently. While the new dense array is very good when needing to look at all xids it is less suitable when accessing a single backend's xid. In particular it would be problematic to have to acquire a lock to access a backend's own xid. Therefore a backend's xid is not just stored in the dense array, but also in PGPROC. This also allows a backend to only access the shared xid value when the backend had acquired an xid. The infrastructure added in this commit will be used for the remaining PGXACT fields in subsequent commits. They are kept separate to make review easier. Author: Andres Freund <andres@anarazel.de> Reviewed-By: Robert Haas <robertmhaas@gmail.com> Reviewed-By: Thomas Munro <thomas.munro@gmail.com> Reviewed-By: David Rowley <dgrowleyml@gmail.com> Discussion: https://postgr.es/m/20200301083601.ews6hz5dduc3w2se@alap3.anarazel.de
* pg_dump: fix dependencies on FKs to partitioned tablesAlvaro Herrera2020-08-14
| | | | | | | | | | | | | | | | | | | | | | | | Parallel-restoring a foreign key that references a partitioned table with several levels of partitions can fail: pg_restore: while PROCESSING TOC: pg_restore: from TOC entry 6684; 2606 29166 FK CONSTRAINT fk fk_a_fkey postgres pg_restore: error: could not execute query: ERROR: there is no unique constraint matching given keys for referenced table "pk" Command was: ALTER TABLE fkpart3.fk ADD CONSTRAINT fk_a_fkey FOREIGN KEY (a) REFERENCES fkpart3.pk(a); This happens in parallel restore mode because some index partitions aren't yet attached to the topmost partitioned index that the FK uses, and so the index is still invalid. The current code marks the FK as dependent on the first level of index-attach dump objects; the bug is fixed by recursively marking the FK on their children. Backpatch to 12, where FKs to partitioned tables were introduced. Reported-by: Tom Lane <tgl@sss.pgh.pa.us> Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Discussion: https://postgr.es/m/3170626.1594842723@sss.pgh.pa.us Backpatch: 12-master
* Fix obsolete comment in xlogutils.c.Peter Geoghegan2020-08-14
| | | | Oversight in commit 2c03216d831.
* Fix postmaster's behavior during smart shutdown.Tom Lane2020-08-14
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Up to now, upon receipt of a SIGTERM ("smart shutdown" command), the postmaster has immediately killed all "optional" background processes, and subsequently refused to launch new ones while it's waiting for foreground client processes to exit. No doubt this seemed like an OK policy at some point; but it's a pretty bad one now, because it makes for a seriously degraded environment for the remaining clients: * Parallel queries are killed, and new ones fail to launch. (And our parallel-query infrastructure utterly fails to deal with the case in a reasonable way --- it just hangs waiting for workers that are not going to arrive. There is more work needed in that area IMO.) * Autovacuum ceases to function. We can tolerate that for awhile, but if bulk-update queries continue to run in the surviving client sessions, there's eventually going to be a mess. In the worst case the system could reach a forced shutdown to prevent XID wraparound. * The bgwriter and walwriter are also stopped immediately, likely resulting in performance degradation. Hence, let's rearrange things so that the only immediate change in behavior is refusing to let in new normal connections. Once the last normal connection is gone, shut everything down as though we'd received a "fast" shutdown. To implement this, remove the PM_WAIT_BACKUP and PM_WAIT_READONLY states, instead staying in PM_RUN or PM_HOT_STANDBY while normal connections remain. A subsidiary state variable tracks whether or not we're letting in new connections in those states. This also allows having just one copy of the logic for killing child processes in smart and fast shutdown modes. I moved that logic into PostmasterStateMachine() by inventing a new state PM_STOP_BACKENDS. Back-patch to 9.6 where parallel query was added. In principle this'd be a good idea in 9.5 as well, but the risk/reward ratio is not as good there, since lack of autovacuum is not a problem during typical uses of smart shutdown. Per report from Bharath Rupireddy. Patch by me, reviewed by Thomas Munro Discussion: https://postgr.es/m/CALj2ACXAZ5vKxT9P7P89D87i3MDO9bfS+_bjMHgnWJs8uwUOOw@mail.gmail.com
* Fix typo in test comment.Heikki Linnakangas2020-08-14
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* Fix compilation warnings with libselinux 3.1 in contrib/sepgsql/Michael Paquier2020-08-14
| | | | | | | | | | | | | | | Upstream SELinux has recently marked security_context_t as officially deprecated, causing warnings with -Wdeprecated-declarations. This is considered as legacy code for some time now by upstream as security_context_t got removed from most of the code tree during the development of 2.3 back in 2014. This removes all the references to security_context_t in sepgsql/ to be consistent with SELinux, fixing the warnings. Note that this does not impact the minimum version of libselinux supported. Reviewed-by: Tom Lane Discussion: https://postgr.es/m/20200813012735.GC11663@paquier.xyz
* Doc: improve examples for json_populate_record() and related functions.Tom Lane2020-08-13
| | | | | | | Make these examples self-contained by providing declarations of the user-defined row types they rely on. There wasn't room to do this in the old doc format, but now there is, and I think it makes the examples a good bit less confusing.
* snapshot scalability: Move PGXACT->xmin back to PGPROC.Andres Freund2020-08-13
| | | | | | | | | | | | | | | | | | | | | | Now that xmin isn't needed for GetSnapshotData() anymore, it leads to unnecessary cacheline ping-pong to have it in PGXACT, as it is updated considerably more frequently than the other PGXACT members. After the changes in dc7420c2c92, this is a very straight-forward change. For highly concurrent, snapshot acquisition heavy, workloads this change alone can significantly increase scalability. E.g. plain pgbench on a smaller 2 socket machine gains 1.07x for read-only pgbench, 1.22x for read-only pgbench when submitting queries in batches of 100, and 2.85x for batches of 100 'SELECT';. The latter numbers are obviously not to be expected in the real-world, but micro-benchmark the snapshot computation scalability (previously spending ~80% of the time in GetSnapshotData()). Author: Andres Freund <andres@anarazel.de> Reviewed-By: Robert Haas <robertmhaas@gmail.com> Reviewed-By: Thomas Munro <thomas.munro@gmail.com> Reviewed-By: David Rowley <dgrowleyml@gmail.com> Discussion: https://postgr.es/m/20200301083601.ews6hz5dduc3w2se@alap3.anarazel.de
* Handle new HOT chains in index-build table scansAlvaro Herrera2020-08-13
| | | | | | | | | | | | | | | | | | | | | | | | | | When a table is scanned by heapam_index_build_range_scan (née IndexBuildHeapScan) and the table lock being held allows concurrent data changes, it is possible for new HOT chains to sprout in a page that were unknown when the scan of a page happened. This leads to an error such as ERROR: failed to find parent tuple for heap-only tuple at (X,Y) in table "tbl" because the root tuple was not present when we first obtained the list of the page's root tuples. This can be fixed by re-obtaining the list of root tuples, if we see that a heap-only tuple appears to point to a non-existing root. This was reported by Anastasia as occurring for BRIN summarization (which exists since 9.5), but I think it could theoretically also happen with CREATE INDEX CONCURRENTLY (much older) or REINDEX CONCURRENTLY (very recent). It seems a happy coincidence that BRIN forces us to backpatch this all the way to 9.5. Reported-by: Anastasia Lubennikova <a.lubennikova@postgrespro.ru> Diagnosed-by: Anastasia Lubennikova <a.lubennikova@postgrespro.ru> Co-authored-by: Anastasia Lubennikova <a.lubennikova@postgrespro.ru> Co-authored-by: Álvaro Herrera <alvherre@alvh.no-ip.org> Discussion: https://postgr.es/m/602d8487-f0b2-5486-0088-0f372b2549fa@postgrespro.ru Backpatch: 9.5 - master
* Fix out-of-date version reference, grammar.Andres Freund2020-08-12
| | | | | | Time appears to be passing fast. Reported-By: Peter Geoghegan <pg@bowt.ie>
* snapshot scalability: Don't compute global horizons while building snapshots.Andres Freund2020-08-12
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | To make GetSnapshotData() more scalable, it cannot not look at at each proc's xmin: While snapshot contents do not need to change whenever a read-only transaction commits or a snapshot is released, a proc's xmin is modified in those cases. The frequency of xmin modifications leads to, particularly on higher core count systems, many cache misses inside GetSnapshotData(), despite the data underlying a snapshot not changing. That is the most significant source of GetSnapshotData() scaling poorly on larger systems. Without accessing xmins, GetSnapshotData() cannot calculate accurate horizons / thresholds as it has so far. But we don't really have to: The horizons don't actually change that much between GetSnapshotData() calls. Nor are the horizons actually used every time a snapshot is built. The trick this commit introduces is to delay computation of accurate horizons until there use and using horizon boundaries to determine whether accurate horizons need to be computed. The use of RecentGlobal[Data]Xmin to decide whether a row version could be removed has been replaces with new GlobalVisTest* functions. These use two thresholds to determine whether a row can be pruned: 1) definitely_needed, indicating that rows deleted by XIDs >= definitely_needed are definitely still visible. 2) maybe_needed, indicating that rows deleted by XIDs < maybe_needed can definitely be removed GetSnapshotData() updates definitely_needed to be the xmin of the computed snapshot. When testing whether a row can be removed (with GlobalVisTestIsRemovableXid()) and the tested XID falls in between the two (i.e. XID >= maybe_needed && XID < definitely_needed) the boundaries can be recomputed to be more accurate. As it is not cheap to compute accurate boundaries, we limit the number of times that happens in short succession. As the boundaries used by GlobalVisTestIsRemovableXid() are never reset (with maybe_needed updated by GetSnapshotData()), it is likely that further test can benefit from an earlier computation of accurate horizons. To avoid regressing performance when old_snapshot_threshold is set (as that requires an accurate horizon to be computed), heap_page_prune_opt() doesn't unconditionally call TransactionIdLimitedForOldSnapshots() anymore. Both the computation of the limited horizon, and the triggering of errors (with SetOldSnapshotThresholdTimestamp()) is now only done when necessary to remove tuples. This commit just removes the accesses to PGXACT->xmin from GetSnapshotData(), but other members of PGXACT residing in the same cache line are accessed. Therefore this in itself does not result in a significant improvement. Subsequent commits will take advantage of the fact that GetSnapshotData() now does not need to access xmins anymore. Note: This contains a workaround in heap_page_prune_opt() to keep the snapshot_too_old tests working. While that workaround is ugly, the tests currently are not meaningful, and it seems best to address them separately. Author: Andres Freund <andres@anarazel.de> Reviewed-By: Robert Haas <robertmhaas@gmail.com> Reviewed-By: Thomas Munro <thomas.munro@gmail.com> Reviewed-By: David Rowley <dgrowleyml@gmail.com> Discussion: https://postgr.es/m/20200301083601.ews6hz5dduc3w2se@alap3.anarazel.de
* BRIN: Handle concurrent desummarization properlyAlvaro Herrera2020-08-12
| | | | | | | | | | | | | | | If a page range is desummarized at just the right time concurrently with an index walk, BRIN would raise an error indicating index corruption. This is scary and unhelpful; silently returning that the page range is not summarized is sufficient reaction. This bug was introduced by commit 975ad4e602ff as additional protection against a bug whose actual fix was elsewhere. Backpatch equally. Reported-By: Anastasia Lubennikova <a.lubennikova@postgrespro.ru> Diagnosed-By: Alexander Lakhin <exclusion@gmail.com> Discussion: https://postgr.es/m/2588667e-d07d-7e10-74e2-7e1e46194491@postgrespro.ru Backpatch: 9.5 - master
* Improve comments for postmaster.c's BackendList.Tom Lane2020-08-12
| | | | | | | | | This had gotten a little disjointed over time, and some of the grammar was sloppy. Rewrite for more clarity. In passing, re-pgindent some recently added comments. No code changes.
* Track latest completed xid as a FullTransactionId.Andres Freund2020-08-11
| | | | | | | | | | | | | | | The reason for doing so is that a subsequent commit will need that to avoid wraparound issues. As the subsequent change is large this was split out for easier review. The reason this is not a perfect straight-forward change is that we do not want track 64bit xids in the procarray or the WAL. Therefore we need to advance lastestCompletedXid in relation to 32 bit xids. The code for that is now centralized in MaintainLatestCompletedXid*. Author: Andres Freund Reviewed-By: Thomas Munro, Robert Haas, David Rowley Discussion: https://postgr.es/m/20200301083601.ews6hz5dduc3w2se@alap3.anarazel.de
* Rename VariableCacheData.nextFullXid to nextXid.Andres Freund2020-08-11
| | | | | | | | | Including Full in variable names duplicates the type information and leads to overly long names. As FullTransactionId cannot accidentally be casted to TransactionId that does not seem necessary. Author: Andres Freund Discussion: https://postgr.es/m/20200724011143.jccsyvsvymuiqfxu@alap3.anarazel.de