564 Commits (d21ded75fdbc18d68be6e6c172f0f842c50e9263)

Author	SHA1	Message	Date
Thomas Munro	cd4329d939	Remove promote_trigger_file. ... Previously, an idle startup (recovery) process would wake up every 5 seconds to have a chance to poll for promote_trigger_file, even if that GUC was not configured. That promotion triggering mechanism was effectively superseded by pg_ctl promote and pg_promote() a long time ago. There probably aren't many users left and it's very easy to change to the modern mechanisms, so we agreed to remove the feature. This is part of a campaign to reduce wakeups on idle systems. Author: Simon Riggs <simon.riggs@enterprisedb.com> Reviewed-by: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com> Reviewed-by: Robert Haas <robertmhaas@gmail.com> Reviewed-by: Thomas Munro <thomas.munro@gmail.com> Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Reviewed-by: Ian Lawrence Barwick <barwick@gmail.com> Discussion: https://postgr.es/m/CANbhV-FsjnzVOQGBpQ589%3DnWuL1Ex0Ykn74Nh1hEjp2usZSR5g%40mail.gmail.com	3 years ago
Tom Lane	f4c7c410ee	Revert "Optimize order of GROUP BY keys". ... This reverts commit db0d67db24 and several follow-on fixes. The idea of making a cost-based choice of the order of the sorting columns is not fundamentally unsound, but it requires cost information and data statistics that we don't really have. For example, relying on procost to distinguish the relative costs of different sort comparators is pretty pointless so long as most such comparator functions are labeled with cost 1.0. Moreover, estimating the number of comparisons done by Quicksort requires more than just an estimate of the number of distinct values in the input: you also need some idea of the sizes of the larger groups, if you want an estimate that's good to better than a factor of three or so. That's data that's often unknown or not very reliable. Worse, to arrive at estimates of the number of calls made to the lower-order-column comparison functions, the code needs to make estimates of the numbers of distinct values of multiple columns, which are necessarily even less trustworthy than per-column stats. Even if all the inputs are perfectly reliable, the cost algorithm as-implemented cannot offer useful information about how to order sorting columns beyond the point at which the average group size is estimated to drop to 1. Close inspection of the code added by db0d67db2 shows that there are also multiple small bugs. These could have been fixed, but there's not much point if we don't trust the estimates to be accurate in-principle. Finally, the changes in cost_sort's behavior made for very large changes (often a factor of 2 or so) in the cost estimates for all sorting operations, not only those for multi-column GROUP BY. That naturally changes plan choices in many situations, and there's precious little evidence to show that the changes are for the better. Given the above doubts about whether the new estimates are really trustworthy, it's hard to summon much confidence that these changes are better on the average. Since we're hard up against the release deadline for v15, let's revert these changes for now. We can always try again later. Note: in v15, I left T_PathKeyInfo in place in nodes.h even though it's unreferenced. Removing it would be an ABI break, and it seems a bit late in the release cycle for that. Discussion: https://postgr.es/m/TYAPR01MB586665EB5FB2C3807E893941F5579@TYAPR01MB5866.jpnprd01.prod.outlook.com	3 years ago
Tom Lane	31dcfae83c	Use the terminology "WAL file" not "log file" more consistently. ... Referring to the WAL as just "log" invites confusion with the postmaster log, so avoid doing that in docs and error messages. Also shorten "WAL segment file" to just "WAL file" in various places. Bharath Rupireddy, reviewed by Nathan Bossart and Kyotaro Horiguchi Discussion: https://postgr.es/m/CALj2ACUeXa8tDPaiTLexBDMZ7hgvaN+RTb957-cn5qwv9zf-MQ@mail.gmail.com	3 years ago
Michael Paquier	0b039e3a84	Fix some inconsistencies with GUC categories ... This commit addresses a few things around GUCs: - The TCP-related parameters (the four tcp_keepalives_* and client_connection_check_interval are listed in postgresql.conf.sample in a subsection called "TCP settings" of "CONNECTIONS AND AUTHENTICATION", but they did not have their own group name in guc.c. - enable_group_by_reordering, stats_fetch_consistency and recovery_prefetch had an inconsistent description, missing a dot at the end. - In postgresql.conf.sample, "Process title" should not have a section of its own, but it should be a subsection of "REPORTING AND LOGGING". This impacts the contents of pg_settings, which could be seen as a compatibility break, so no backpatch is done. This is similar to the cleanup done in a55a984. Author: Shinya Kato Discussion: https://postgr.es/m/5e0c9c608624eafbba910c344282cb14@oss.nttdata.com	3 years ago
Thomas Munro	94ebf8117c	Default to dynamic_shared_memory_type=sysv on Solaris. ... POSIX shm_open() can sleep for a long time and fail spuriously because of contention on an internal lock file on Solaris (and presumably illumos). Commit 389869af fixed the main problem with this, namely that we could crash, but it's now clear that "posix" is not a good default. Therefore, choose "sysv" at initdb time on Solaris and illumos. Other choices are still available by editing the postgresql.conf file. Back-patch only to 15, because contention is much less likely further back, and it doesn't seem like a good idea to change this in released branches. This should clear up the failures on build farm animal margay. Discussion: https://postgr.es/m/CA%2BhUKGKqKrCV5xKWfh9rnm%3Do%3DDwZLTLtnsj_XpUi9g5%3DV%2B9oyg%40mail.gmail.com	4 years ago
Andres Freund	98f897339b	Fix stats_fetch_consistency default value indicated in postgresql.conf.sample. ... Mistake in 5891c7a8ed, likely made when switching the default value from none to fetch during development. Reported-By: Nathan Bossart <nathandbossart@gmail.com> Author: Nathan Bossart <nathandbossart@gmail.com> Discussion: https://postgr.es/m/20220524220147.GA1298892@nathanxps13	4 years ago
Peter Eisentraut	9700b250c5	Formatting and punctuation improvements in sample configuration files	4 years ago
Thomas Munro	5dc0418fab	Prefetch data referenced by the WAL, take II. ... Introduce a new GUC recovery_prefetch. When enabled, look ahead in the WAL and try to initiate asynchronous reading of referenced data blocks that are not yet cached in our buffer pool. For now, this is done with posix_fadvise(), which has several caveats. Since not all OSes have that system call, "try" is provided so that it can be enabled where available. Better mechanisms for asynchronous I/O are possible in later work. Set to "try" for now for test coverage. Default setting to be finalized before release. The GUC wal_decode_buffer_size limits the distance we can look ahead in bytes of decoded data. The existing GUC maintenance_io_concurrency is used to limit the number of concurrent I/Os allowed, based on pessimistic heuristics used to infer that I/Os have begun and completed. We'll also not look more than maintenance_io_concurrency * 4 block references ahead. Reviewed-by: Julien Rouhaud <rjuju123@gmail.com> Reviewed-by: Tomas Vondra <tomas.vondra@2ndquadrant.com> Reviewed-by: Alvaro Herrera <alvherre@2ndquadrant.com> (earlier version) Reviewed-by: Andres Freund <andres@anarazel.de> (earlier version) Reviewed-by: Justin Pryzby <pryzby@telsasoft.com> (earlier version) Tested-by: Tomas Vondra <tomas.vondra@2ndquadrant.com> (earlier version) Tested-by: Jakub Wartak <Jakub.Wartak@tomtom.com> (earlier version) Tested-by: Dmitry Dolgov <9erthalion6@gmail.com> (earlier version) Tested-by: Sait Talha Nisanci <Sait.Nisanci@microsoft.com> (earlier version) Discussion: https://postgr.es/m/CA%2BhUKGJ4VJN8ttxScUFM8dOKX0BrBiboo5uz1cq%3DAovOddfHpA%40mail.gmail.com	4 years ago
Andres Freund	1db4e5a4ee	pgstat: rename STATS_COLLECTOR GUC group to STATS_CUMULATIVE. ... Reviewed-By: Kyotaro Horiguchi <horikyota.ntt@gmail.com> Author: Andres Freund <andres@anarazel.de> Discussion: https://postgr.es/m/20220303021600.hs34ghqcw6zcokdh@alap3.anarazel.de	4 years ago
Andres Freund	6f0cf87872	pgstat: remove stats_temp_directory. ... With stats now being stored in shared memory, the GUC isn't needed anymore. However, the pg_stat_tmp directory and PG_STAT_TMP_DIR define are kept, as pg_stat_statements (and some out-of-core extensions) store data in it. Docs will be updated in a subsequent commit, together with the other pending docs updates due to shared memory stats. Author: Andres Freund <andres@anarazel.de> Author: Kyotaro Horiguchi <horikyota.ntt@gmail.com> Reviewed-By: Kyotaro Horiguchi <horikyota.ntt@gmail.com> Discussion: https://postgr.es/m/20220330233550.eiwsbearu6xhuqwe@alap3.anarazel.de Discussion: https://postgr.es/m/20220303021600.hs34ghqcw6zcokdh@alap3.anarazel.de	4 years ago
Andres Freund	5891c7a8ed	pgstat: store statistics in shared memory. ... Previously the statistics collector received statistics updates via UDP and shared statistics data by writing them out to temporary files regularly. These files can reach tens of megabytes and are written out up to twice a second. This has repeatedly prevented us from adding additional useful statistics. Now statistics are stored in shared memory. Statistics for variable-numbered objects are stored in a dshash hashtable (backed by dynamic shared memory). Fixed-numbered stats are stored in plain shared memory. The header for pgstat.c contains an overview of the architecture. The stats collector is not needed anymore, remove it. By utilizing the transactional statistics drop infrastructure introduced in a prior commit statistics entries cannot "leak" anymore. Previously leaked statistics were dropped by pgstat_vacuum_stat(), called from [auto-]vacuum. On systems with many small relations pgstat_vacuum_stat() could be quite expensive. Now that replicas drop statistics entries for dropped objects, it is not necessary anymore to reset stats when starting from a cleanly shut down replica. Subsequent commits will perform some further code cleanup, adapt docs and add tests. Bumps PGSTAT_FILE_FORMAT_ID. Author: Kyotaro Horiguchi <horikyota.ntt@gmail.com> Author: Andres Freund <andres@anarazel.de> Author: Melanie Plageman <melanieplageman@gmail.com> Reviewed-By: Andres Freund <andres@anarazel.de> Reviewed-By: Thomas Munro <thomas.munro@gmail.com> Reviewed-By: Justin Pryzby <pryzby@telsasoft.com> Reviewed-By: "David G. Johnston" <david.g.johnston@gmail.com> Reviewed-By: Tomas Vondra <tomas.vondra@2ndquadrant.com> (in a much earlier version) Reviewed-By: Arthur Zakirov <a.zakirov@postgrespro.ru> (in a much earlier version) Reviewed-By: Antonin Houska <ah@cybertec.at> (in a much earlier version) Discussion: https://postgr.es/m/20220303021600.hs34ghqcw6zcokdh@alap3.anarazel.de Discussion: https://postgr.es/m/20220308205351.2xcn6k4x5yivcxyd@alap3.anarazel.de Discussion: https://postgr.es/m/20210319235115.y3wz7hpnnrshdyv6@alap3.anarazel.de	4 years ago
Tomas Vondra	db0d67db24	Optimize order of GROUP BY keys ... When evaluating a query with a multi-column GROUP BY clause using sort, the cost may be heavily dependent on the order in which the keys are compared when building the groups. Grouping does not imply any ordering, so we're allowed to compare the keys in arbitrary order, and a Hash Agg leverages this. But for Group Agg, we simply compared keys in the order as specified in the query. This commit explores alternative ordering of the keys, trying to find a cheaper one. In principle, we might generate grouping paths for all permutations of the keys, and leave the rest to the optimizer. But that might get very expensive, so we try to pick only a couple interesting orderings based on both local and global information. When planning the grouping path, we explore statistics (number of distinct values, cost of the comparison function) for the keys and reorder them to minimize comparison costs. Intuitively, it may be better to perform more expensive comparisons (for complex data types etc.) last, because maybe the cheaper comparisons will be enough. Similarly, the higher the cardinality of a key, the lower the probability we’ll need to compare more keys. The patch generates and costs various orderings, picking the cheapest ones. The ordering of group keys may interact with other parts of the query, some of which may not be known while planning the grouping. E.g. there may be an explicit ORDER BY clause, or some other ordering-dependent operation, higher up in the query, and using the same ordering may allow using either incremental sort or even eliminate the sort entirely. The patch generates orderings and picks those minimizing the comparison cost (for various pathkeys), and then adds orderings that might be useful for operations higher up in the plan (ORDER BY, etc.). Finally, it always keeps the ordering specified in the query, on the assumption the user might have additional insights. This introduces a new GUC enable_group_by_reordering, so that the optimization may be disabled if needed. The original patch was proposed by Teodor Sigaev, and later improved and reworked by Dmitry Dolgov. Reviews by a number of people, including me, Andrey Lepikhov, Claudio Freire, Ibrar Ahmed and Zhihong Yu. Author: Dmitry Dolgov, Teodor Sigaev, Tomas Vondra Reviewed-by: Tomas Vondra, Andrey Lepikhov, Claudio Freire, Ibrar Ahmed, Zhihong Yu Discussion: https://postgr.es/m/7c79e6a5-8597-74e8-0671-1c39d124c9d6%40sigaev.ru Discussion: https://postgr.es/m/CA%2Bq6zcW_4o2NC0zutLkOJPsFt80megSpX_dVRo6GK9PC-Jx_Ag%40mail.gmail.com	4 years ago
Tom Lane	0bd7af082a	Invent recursive_worktable_factor GUC to replace hard-wired constant. ... Up to now, the planner estimated the size of a recursive query's worktable as 10 times the size of the non-recursive term. It's hard to see how to do significantly better than that automatically, but we can give users control over the multiplier to allow tuning for specific use-cases. The default behavior remains the same. Simon Riggs Discussion: https://postgr.es/m/CANbhV-EuaLm4H3g0+BSTYHEGxJj3Kht0R+rJ8vT57Dejnh=_nA@mail.gmail.com	4 years ago
Michael Paquier	e9537321a7	Add support for zstd with compression of full-page writes in WAL ... wal_compression gains a new value, "zstd", to allow the compression of full-page images using the compression method of the same name. Compression is done using the default level recommended by the library, as of ZSTD_CLEVEL_DEFAULT = 3. Some benchmarking has shown that it could make sense to use a level lower for the FPI compression, like 1 or 2, as the compression rate did not change much with a bit less CPU consumed, but any tests done would only cover few scenarios so it is hard to come to a clear conclusion. Anyway, there is no reason to not use the default level instead, which is the level recommended by the library so it should be fine for most cases. zstd outclasses easily pglz, and is better than LZ4 where one wants to have more compression at the cost of extra CPU but both are good enough in their own scenarios, so the choice between one or the other of these comes to a study of the workload patterns and the schema involved, mainly. This commit relies heavily on 4035cd5, that reshaped the code creating and restoring full-page writes to be aware of the compression type, making this integration straight-forward. This patch borrows some early work from Andrey Borodin, though the patch got a complete rewrite. Author: Justin Pryzby Discussion: https://postgr.es/m/20220222231948.GJ9008@telsasoft.com	4 years ago
Peter Geoghegan	8f388f6f55	Increase hash_mem_multiplier default to 2.0. ... Double the default setting for hash_mem_multiplier, from 1.0 to 2.0. This setting makes hash-based executor nodes use twice the usual work_mem limit. The PostgreSQL 15 release notes should have a compatibility note about this change. Author: Peter Geoghegan <pg@bowt.ie> Discussion: https://postgr.es/m/CAH2-Wzndc_ROk6CY-bC6p9O53q974Y0Ey4WX8jcPbuTZYM4Q3A@mail.gmail.com	4 years ago
Robert Haas	5ef1eefd76	Allow archiving via loadable modules. ... Running a shell command for each file to be archived has a lot of overhead and may not offer as much error checking as you want, or the exact semantics that you want. So, offer the option to call a loadable module for each file to be archived, rather than running a shell command. Also, add a 'basic_archive' contrib module as an example implementation that archives to a local directory. Nathan Bossart, with a little bit of kibitzing by me. Discussion: http://postgr.es/m/20220202224433.GA1036711@nathanxps13	4 years ago
Michael Paquier	dc686681e0	Introduce log_destination=jsonlog ... "jsonlog" is a new value that can be added to log_destination to provide logs in the JSON format, with its output written to a file, making it the third type of destination of this kind, after "stderr" and "csvlog". The format is convenient to feed logs to other applications. There is also a plugin external to core that provided this feature using the hook in elog.c, but this had to overwrite the output of "stderr" to work, so being able to do both at the same time was not possible. The files generated by this log format are suffixed with ".json", and use the same rotation policies as the other two formats depending on the backend configuration. This takes advantage of the refactoring work done previously in ac7c807, bed6ed3, 8b76f89 and 2d77d83 for the backend parts, and 72b76f7 for the TAP tests, making the addition of any new file-based format rather straight-forward. The documentation is updated to list all the keys and the values that can exist in this new format. pg_current_logfile() also required a refresh for the new option. Author: Sehrope Sarkuni, Michael Paquier Reviewed-by: Nathan Bossart, Justin Pryzby Discussion: https://postgr.es/m/CAH7T-aqswBM6JWe4pDehi1uOiufqe06DJWaU5=X7dDLyqUExHg@mail.gmail.com	4 years ago
Robert Haas	64da07c41a	Default to log_checkpoints=on, log_autovacuum_min_duration=10m ... The idea here is that when a performance problem is known to have occurred at a certain point in time, it's a good thing if there is some information available from the logs to help figure out what might have happened around that time. This change attracted an above-average amount of dissent, because it means that a server with default settings will produce some amount of log output even if nothing has gone wrong. However, by my count, the mailing list discussion had about twice as many people in favor of the change as opposed. The reasons for believing that the extra log output is not an issue in practice are: (1) the rate at which messages can be generated by this setting is bounded to one every few minutes on a properly-configured system and (2) production systems tend to have a lot more junk in the log from that due to failed connection attempts, ERROR messages generated by application activity, and the like. Bharath Rupireddy, reviewed by Fujii Masao and by me. Many other people commented on the thread, but as far as I can see that was discussion of the merits of the change rather than review of the patch. Discussion: https://postgr.es/m/CALj2ACX-rW_OeDcp4gqrFUAkf1f50Fnh138dmkd0JkvCNQRKGA@mail.gmail.com	4 years ago
Robert Haas	9ce346eabf	Report progress of startup operations that take a long time. ... Users sometimes get concerned whe they start the server and it emits a few messages and then doesn't emit any more messages for a long time. Generally, what's happening is either that the system is taking a long time to apply WAL, or it's taking a long time to reset unlogged relations, or it's taking a long time to fsync the data directory, but it's not easy to tell which is the case. To fix that, add a new 'log_startup_progress_interval' setting, by default 10s. When an operation that is known to be potentially long-running takes more than this amount of time, we'll log a status update each time this interval elapses. To avoid undesirable log chatter, don't log anything about WAL replay when in standby mode. Nitin Jadhav and Robert Haas, reviewed by Amul Sul, Bharath Rupireddy, Justin Pryzby, Michael Paquier, and Álvaro Herrera. Discussion: https://postgr.es/m/CA+TgmoaHQrgDFOBwgY16XCoMtXxsrVGFB2jNCvb7-ubuEe1MGg@mail.gmail.com Discussion: https://postgr.es/m/CAMm1aWaHF7VE69572_OLQ+MgpT5RUiUDgF1x5RrtkJBLdpRj3Q@mail.gmail.com	4 years ago
Bruce Momjian	f7bda63a48	Improve defaults shown in postgresql.conf.sample and pg_settings ... Previously, these showed unlikely default values. The new default value 128MB (since PG 10) is not always accurate since initdb tries several increasing values, but it likely to be accurate. Reported-by: Zhangjie <zhangjie2@fujitsu.com> Discussion: https://postgr.es/m/TYWPR01MB7678772FD8640C404F1DC882F9079@TYWPR01MB7678.jpnprd01.prod.outlook.com Author: Zhangjie Backpatch-through: master	4 years ago
John Naylor	bb95feabb8	Document "B" and "us" as accepted units in postgres.conf.sample ... In postgresql.conf, memory and file size GUCs can be specified with "B" (bytes) as of b06d8e58b. Likewise, time GUCs can be specified with "us" (microseconds) as of caf626b2c. Update postgres.conf.sample to reflect that fact. Pavel Luzanov Backpatch to v12, which is the earliest version that allows both of these units. A separate commit will document the "B" case for v11. Discussion: https://www.postgresql.org/message-id/flat/f10d16fc-8fa0-1b3c-7371-cb3a35a13b7a%40postgrespro.ru	4 years ago
David Rowley	83f4fcc655	Change the name of the Result Cache node to Memoize ... "Result Cache" was never a great name for this node, but nobody managed to come up with another name that anyone liked enough. That was until David Johnston mentioned "Node Memoization", which Tom Lane revised to just "Memoize". People seem to like "Memoize", so let's do the rename. Reviewed-by: Justin Pryzby Discussion: https://postgr.es/m/20210708165145.GG1176@momjian.us Backpatch-through: 14, where Result Cache was introduced	5 years ago
Michael Paquier	4035cd5d4e	Add support for LZ4 with compression of full-page writes in WAL ... The logic is implemented so as there can be a choice in the compression used when building a WAL record, and an extra per-record bit is used to track down if a block is compressed with PGLZ, LZ4 or nothing. wal_compression, the existing parameter, is changed to an enum with support for the following backward-compatible values: - "off", the default, to not use compression. - "pglz" or "on", to compress FPWs with PGLZ. - "lz4", the new mode, to compress FPWs with LZ4. Benchmarking has showed that LZ4 outclasses easily PGLZ. ZSTD would be also an interesting choice, but going just with LZ4 for now makes the patch minimalistic as toast compression is already able to use LZ4, so there is no need to worry about any build-related needs for this implementation. Author: Andrey Borodin, Justin Pryzby Reviewed-by: Dilip Kumar, Michael Paquier Discussion: https://postgr.es/m/3037310D-ECB7-4BF1-AF20-01C10BB33A33@yandex-team.ru	5 years ago
Thomas Munro	34a8b64b4e	Change recovery_init_sync_method to PGC_SIGHUP. ... The setting has no effect except during startup. It's still nice to be able to change it dynamically, which is expected to be pretty useful to an admin following crash recovery when restarting the cluster is not so appealing. Per discussions following commits 2941138e6 and 61752afb2. Author: Justin Pryzby <pryzby@telsasoft.com> Reviewed-by: Fujii Masao <masao.fujii@oss.nttdata.com> Reviewed-by: Michael Paquier <michael@paquier.xyz> Reviewed-by: Thomas Munro <thomas.munro@gmail.com> Discussion: https://postgr.es/m/20210529192321.GM2082%40telsasoft.com	5 years ago
Michael Paquier	797b0fc0b0	doc: Move remove_temp_files_after_crash to section for developer options ... The main goal of this option is to allow inspecting temporary files for debugging purposes, so moving the parameter there is natural. Oversight in cd91de0. Reported-by: Justin Pryzby Author: Euler Taveira Discussion: https://postgr.es/m/20210612004347.GP16435@telsasoft.com	5 years ago
Michael Paquier	2941138e60	doc: Fix description of some GUCs in docs and postgresql.conf.sample ... The following parameters have been imprecise, or incorrect, about their description (PGC_POSTMASTER or PGC_SIGHUP): - autovacuum_work_mem (docs, as of 9.6~) - huge_page_size (docs, as of 14~) - max_logical_replication_workers (docs, as of 10~) - max_sync_workers_per_subscription (docs, as of 10~) - min_dynamic_shared_memory (docs, as of 14~) - recovery_init_sync_method (postgresql.conf.sample, as of 14~) - remove_temp_files_after_crash (docs, as of 14~) - restart_after_crash (docs, as of 9.6~) - ssl_min_protocol_version (docs, as of 12~) - ssl_max_protocol_version (docs, as of 12~) This commit adjusts the description of all these parameters to be more consistent with the practice used for the others. Revewed-by: Justin Pryzby Discussion: https://postgr.es/m/YK2ltuLpe+FbRXzA@paquier.xyz Backpatch-through: 9.6	5 years ago
Peter Eisentraut	8673a37c85	postgresql.conf.sample: Make vertical spacing consistent	5 years ago
Alvaro Herrera	cafde58b33	Allow compute_query_id to be set to 'auto' and make it default ... Allowing only on/off meant that all either all existing configuration guides would become obsolete if we disabled it by default, or that we would have to accept a performance loss in the default config if we enabled it by default. By allowing 'auto' as a middle ground, the performance cost is only paid by those who enable pg_stat_statements and similar modules. I only edited the release notes to comment-out a paragraph that is now factually wrong; further edits are probably needed to describe the related change in more detail. Author: Julien Rouhaud <rjuju123@gmail.com> Reviewed-by: Justin Pryzby <pryzby@telsasoft.com> Discussion: https://postgr.es/m/20210513002623.eugftm4nk2lvvks3@nol	5 years ago
Thomas Munro	c2dc19342e	Revert recovery prefetching feature. ... This set of commits has some bugs with known fixes, but at this late stage in the release cycle it seems best to revert and resubmit next time, along with some new automated test coverage for this whole area. Commits reverted: dc88460c: Doc: Review for "Optionally prefetch referenced data in recovery." 1d257577: Optionally prefetch referenced data in recovery. f003d9f8: Add circular WAL decoding buffer. 323cbe7c: Remove read_page callback from XLogReader. Remove the new GUC group WAL_RECOVERY recently added by a55a9847, as the corresponding section of config.sgml is now reverted. Discussion: https://postgr.es/m/CAOuzzgrn7iKnFRsB4MHp3UisEQAGgZMbk_ViTN4HV4-Ksq8zCg%40mail.gmail.com	5 years ago
Tom Lane	a55a98477b	Sync guc.c and postgresql.conf.sample with the SGML docs. ... It seems that various people have moved GUCs around in the config.sgml listing without bothering to make the code agree. Ensure that the config_group codes assigned to GUCs match where they are listed in config.sgml. Likewise ensure that postgresql.conf.sample lists GUCs in the same sub-section and same ordering as they appear in config.sgml. (I've got some doubts about some of these choices, but for the purposes of this patch, we'll treat config.sgml as gospel.) Notably, this requires adding a WAL_RECOVERY config_group value, because 1d257577e didn't. As long as we're renumbering that enum anyway, let's take out the values corresponding to major groups that are divided into sub-groups. No GUC should be assigned to the major group itself, so those values just create a temptation to do the wrong thing, while adding work for translators. In passing, adjust the short_desc strings for PRESET_OPTIONS GUCs to uniformly use the phrasing "Shows XYZ.", removing the impression some of these strings left that you can set the value. While some of these errors are old, no back-patch, as changing the contents of the pg_settings view in stable branches seems more likely to be seen as a compatibility break than anything helpful. Bharath Rupireddy, Justin Pryzby, Tom Lane Discussion: https://postgr.es/m/16997-ff16127f6e0d1390@postgresql.org Discussion: https://postgr.es/m/20210413123139.GE6091@telsasoft.com	5 years ago
Michael Paquier	ac725ee0f9	doc: Move force_parallel_mode to section for developer options ... This GUC has always been classified as a planner option since its introduction in 7c944bd, and was listed in postgresql.conf.sample. As this parameter exists for testing purposes, move it to the section dedicated to developer parameters and hence remove it from postgresql.conf.sample. This will avoid any temptation to play with it on production servers for users that should never really have to touch this parameter. The general description used for developer options is reworded a bit, to take into account the inclusion of force_parallel_mode, per a suggestion from Tom Lane. Per discussion between Tom Lane, Bruce Momjian, Justin Pryzby, Bharath Rupireddy and me. Author: Justin Pryzby, Tom Lane Discussion: https://postgr.es/m/20210403152402.GA8049@momjian.us	5 years ago
Michael Paquier	b094063cd1	Move log_autovacuum_min_duration into its correct sections ... This GUC has already been classified as LOGGING_WHAT, but its location in postgresql.conf.sample and the documentation did not reflect that, so fix those inconsistencies. Author: Justin Pryzby Discussion: https://postgr.es/m/20210404012546.GK6592@telsasoft.com	5 years ago
Thomas Munro	1d257577e0	Optionally prefetch referenced data in recovery. ... Introduce a new GUC recovery_prefetch, disabled by default. When enabled, look ahead in the WAL and try to initiate asynchronous reading of referenced data blocks that are not yet cached in our buffer pool. For now, this is done with posix_fadvise(), which has several caveats. Better mechanisms will follow in later work on the I/O subsystem. The GUC maintenance_io_concurrency is used to limit the number of concurrent I/Os we allow ourselves to initiate, based on pessimistic heuristics used to infer that I/Os have begun and completed. The GUC wal_decode_buffer_size is used to limit the maximum distance we are prepared to read ahead in the WAL to find uncached blocks. Reviewed-by: Alvaro Herrera <alvherre@2ndquadrant.com> (parts) Reviewed-by: Andres Freund <andres@anarazel.de> (parts) Reviewed-by: Tomas Vondra <tomas.vondra@2ndquadrant.com> (parts) Tested-by: Tomas Vondra <tomas.vondra@2ndquadrant.com> Tested-by: Jakub Wartak <Jakub.Wartak@tomtom.com> Tested-by: Dmitry Dolgov <9erthalion6@gmail.com> Tested-by: Sait Talha Nisanci <Sait.Nisanci@microsoft.com> Discussion: https://postgr.es/m/CA%2BhUKGJ4VJN8ttxScUFM8dOKX0BrBiboo5uz1cq%3DAovOddfHpA%40mail.gmail.com	5 years ago
Peter Geoghegan	1e55e7d175	Add wraparound failsafe to VACUUM. ... Add a failsafe mechanism that is triggered by VACUUM when it notices that the table's relfrozenxid and/or relminmxid are dangerously far in the past. VACUUM checks the age of the table dynamically, at regular intervals. When the failsafe triggers, VACUUM takes extraordinary measures to finish as quickly as possible so that relfrozenxid and/or relminmxid can be advanced. VACUUM will stop applying any cost-based delay that may be in effect. VACUUM will also bypass any further index vacuuming and heap vacuuming -- it only completes whatever remaining pruning and freezing is required. Bypassing index/heap vacuuming is enabled by commit 8523492d, which made it possible to dynamically trigger the mechanism already used within VACUUM when it is run with INDEX_CLEANUP off. It is expected that the failsafe will almost always trigger within an autovacuum to prevent wraparound, long after the autovacuum began. However, the failsafe mechanism can trigger in any VACUUM operation. Even in a non-aggressive VACUUM, where we're likely to not advance relfrozenxid, it still seems like a good idea to finish off remaining pruning and freezing. An aggressive/anti-wraparound VACUUM will be launched immediately afterwards. Note that the anti-wraparound VACUUM that follows will itself trigger the failsafe, usually before it even begins its first (and only) pass over the heap. The failsafe is controlled by two new GUCs: vacuum_failsafe_age, and vacuum_multixact_failsafe_age. There are no equivalent reloptions, since that isn't expected to be useful. The GUCs have rather high defaults (both default to 1.6 billion), and are expected to generally only be used to make the failsafe trigger sooner/more frequently. Author: Masahiko Sawada <sawada.mshk@gmail.com> Author: Peter Geoghegan <pg@bowt.ie> Discussion: https://postgr.es/m/CAD21AoD0SkE11fMw4jD4RENAwBMcw1wasVnwpJVw3tVqPOQgAw@mail.gmail.com Discussion: https://postgr.es/m/CAH2-WzmgH3ySGYeC-m-eOBsa2=sDwa292-CFghV4rESYo39FsQ@mail.gmail.com	5 years ago
Bruce Momjian	4f0b0966c8	Make use of in-core query id added by commit 5fd9dfa5f5 ... Use the in-core query id computation for pg_stat_activity, log_line_prefix, and EXPLAIN VERBOSE. Similar to other fields in pg_stat_activity, only the queryid from the top level statements are exposed, and if the backends status isn't active then the queryid from the last executed statements is displayed. Add a %Q placeholder to include the queryid in log_line_prefix, which will also only expose top level statements. For EXPLAIN VERBOSE, if a query identifier has been computed, either by enabling compute_query_id or using a third-party module, display it. Bump catalog version. Discussion: https://postgr.es/m/20210407125726.tkvjdbw76hxnpwfi@nol Author: Julien Rouhaud Reviewed-by: Alvaro Herrera, Nitin Jadhav, Zhihong Yu	5 years ago
Bruce Momjian	5fd9dfa5f5	Move pg_stat_statements query jumbling to core. ... Add compute_query_id GUC to control whether a query identifier should be computed by the core (off by default). It's thefore now possible to disable core queryid computation and use pg_stat_statements with a different algorithm to compute the query identifier by using a third-party module. To ensure that a single source of query identifier can be used and is well defined, modules that calculate a query identifier should throw an error if compute_query_id specified to compute a query id and if a query idenfitier was already calculated. Discussion: https://postgr.es/m/20210407125726.tkvjdbw76hxnpwfi@nol Author: Julien Rouhaud Reviewed-by: Alvaro Herrera, Nitin Jadhav, Zhihong Yu	5 years ago
Thomas Munro	c30f54ad73	Detect POLLHUP/POLLRDHUP while running queries. ... Provide a new GUC check_client_connection_interval that can be used to check whether the client connection has gone away, while running very long queries. It is disabled by default. For now this uses a non-standard Linux extension (also adopted by at least one other OS). POLLRDHUP is not defined by POSIX, and other OSes don't have a reliable way to know if a connection was closed without actually trying to read or write. In future we might consider trying to send a no-op/heartbeat message instead, but that could require protocol changes. Author: Sergey Cherkashin <s.cherkashin@postgrespro.ru> Author: Thomas Munro <thomas.munro@gmail.com> Reviewed-by: Thomas Munro <thomas.munro@gmail.com> Reviewed-by: Tatsuo Ishii <ishii@sraoss.co.jp> Reviewed-by: Konstantin Knizhnik <k.knizhnik@postgrespro.ru> Reviewed-by: Zhihong Yu <zyu@yugabyte.com> Reviewed-by: Andres Freund <andres@anarazel.de> Reviewed-by: Maksim Milyutin <milyutinma@gmail.com> Reviewed-by: Tsunakawa, Takayuki/綱川 貴之 <tsunakawa.takay@fujitsu.com> Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> (much earlier version) Discussion: https://postgr.es/m/77def86b27e41f0efcba411460e929ae%40postgrespro.ru	5 years ago
David Rowley	9eacee2e62	Add Result Cache executor node (take 2) ... Here we add a new executor node type named "Result Cache". The planner can include this node type in the plan to have the executor cache the results from the inner side of parameterized nested loop joins. This allows caching of tuples for sets of parameters so that in the event that the node sees the same parameter values again, it can just return the cached tuples instead of rescanning the inner side of the join all over again. Internally, result cache uses a hash table in order to quickly find tuples that have been previously cached. For certain data sets, this can significantly improve the performance of joins. The best cases for using this new node type are for join problems where a large portion of the tuples from the inner side of the join have no join partner on the outer side of the join. In such cases, hash join would have to hash values that are never looked up, thus bloating the hash table and possibly causing it to multi-batch. Merge joins would have to skip over all of the unmatched rows. If we use a nested loop join with a result cache, then we only cache tuples that have at least one join partner on the outer side of the join. The benefits of using a parameterized nested loop with a result cache increase when there are fewer distinct values being looked up and the number of lookups of each value is large. Also, hash probes to lookup the cache can be much faster than the hash probe in a hash join as it's common that the result cache's hash table is much smaller than the hash join's due to result cache only caching useful tuples rather than all tuples from the inner side of the join. This variation in hash probe performance is more significant when the hash join's hash table no longer fits into the CPU's L3 cache, but the result cache's hash table does. The apparent "random" access of hash buckets with each hash probe can cause a poor L3 cache hit ratio for large hash tables. Smaller hash tables generally perform better. The hash table used for the cache limits itself to not exceeding work_mem * hash_mem_multiplier in size. We maintain a dlist of keys for this cache and when we're adding new tuples and realize we've exceeded the memory budget, we evict cache entries starting with the least recently used ones until we have enough memory to add the new tuples to the cache. For parameterized nested loop joins, we now consider using one of these result cache nodes in between the nested loop node and its inner node. We determine when this might be useful based on cost, which is primarily driven off of what the expected cache hit ratio will be. Estimating the cache hit ratio relies on having good distinct estimates on the nested loop's parameters. For now, the planner will only consider using a result cache for parameterized nested loop joins. This works for both normal joins and also for LATERAL type joins to subqueries. It is possible to use this new node for other uses in the future. For example, to cache results from correlated subqueries. However, that's not done here due to some difficulties obtaining a distinct estimation on the outer plan to calculate the estimated cache hit ratio. Currently we plan the inner plan before planning the outer plan so there is no good way to know if a result cache would be useful or not since we can't estimate the number of times the subplan will be called until the outer plan is generated. The functionality being added here is newly introducing a dependency on the return value of estimate_num_groups() during the join search. Previously, during the join search, we only ever needed to perform selectivity estimations. With this commit, we need to use estimate_num_groups() in order to estimate what the hit ratio on the result cache will be. In simple terms, if we expect 10 distinct values and we expect 1000 outer rows, then we'll estimate the hit ratio to be 99%. Since cache hits are very cheap compared to scanning the underlying nodes on the inner side of the nested loop join, then this will significantly reduce the planner's cost for the join. However, it's fairly easy to see here that things will go bad when estimate_num_groups() incorrectly returns a value that's significantly lower than the actual number of distinct values. If this happens then that may cause us to make use of a nested loop join with a result cache instead of some other join type, such as a merge or hash join. Our distinct estimations have been known to be a source of trouble in the past, so the extra reliance on them here could cause the planner to choose slower plans than it did previous to having this feature. Distinct estimations are also fairly hard to estimate accurately when several tables have been joined already or when a WHERE clause filters out a set of values that are correlated to the expressions we're estimating the number of distinct value for. For now, the costing we perform during query planning for result caches does put quite a bit of faith in the distinct estimations being accurate. When these are accurate then we should generally see faster execution times for plans containing a result cache. However, in the real world, we may find that we need to either change the costings to put less trust in the distinct estimations being accurate or perhaps even disable this feature by default. There's always an element of risk when we teach the query planner to do new tricks that it decides to use that new trick at the wrong time and causes a regression. Users may opt to get the old behavior by turning the feature off using the enable_resultcache GUC. Currently, this is enabled by default. It remains to be seen if we'll maintain that setting for the release. Additionally, the name "Result Cache" is the best name I could think of for this new node at the time I started writing the patch. Nobody seems to strongly dislike the name. A few people did suggest other names but no other name seemed to dominate in the brief discussion that there was about names. Let's allow the beta period to see if the current name pleases enough people. If there's some consensus on a better name, then we can change it before the release. Please see the 2nd discussion link below for the discussion on the "Result Cache" name. Author: David Rowley Reviewed-by: Andy Fan, Justin Pryzby, Zhihong Yu, Hou Zhijie Tested-By: Konstantin Knizhnik Discussion: https://postgr.es/m/CAApHDvrPcQyQdWERGYWx8J%2B2DLUNgXu%2BfOSbQ1UscxrunyXyrQ%40mail.gmail.com Discussion: https://postgr.es/m/CAApHDvq=yQXr5kqhRviT2RhNKwToaWr9JAN5t+5_PzhuRJ3wvg@mail.gmail.com	5 years ago
David Rowley	28b3e3905c	Revert b6002a796 ... This removes "Add Result Cache executor node". It seems that something weird is going on with the tracking of cache hits and misses as highlighted by many buildfarm animals. It's not yet clear what the problem is as other parts of the plan indicate that the cache did work correctly, it's just the hits and misses that were being reported as 0. This is especially a bad time to have the buildfarm so broken, so reverting before too many more animals go red. Discussion: https://postgr.es/m/CAApHDvq_hydhfovm4=izgWs+C5HqEeRScjMbOgbpC-jRAeK3Yw@mail.gmail.com	5 years ago
David Rowley	b6002a796d	Add Result Cache executor node ... Here we add a new executor node type named "Result Cache". The planner can include this node type in the plan to have the executor cache the results from the inner side of parameterized nested loop joins. This allows caching of tuples for sets of parameters so that in the event that the node sees the same parameter values again, it can just return the cached tuples instead of rescanning the inner side of the join all over again. Internally, result cache uses a hash table in order to quickly find tuples that have been previously cached. For certain data sets, this can significantly improve the performance of joins. The best cases for using this new node type are for join problems where a large portion of the tuples from the inner side of the join have no join partner on the outer side of the join. In such cases, hash join would have to hash values that are never looked up, thus bloating the hash table and possibly causing it to multi-batch. Merge joins would have to skip over all of the unmatched rows. If we use a nested loop join with a result cache, then we only cache tuples that have at least one join partner on the outer side of the join. The benefits of using a parameterized nested loop with a result cache increase when there are fewer distinct values being looked up and the number of lookups of each value is large. Also, hash probes to lookup the cache can be much faster than the hash probe in a hash join as it's common that the result cache's hash table is much smaller than the hash join's due to result cache only caching useful tuples rather than all tuples from the inner side of the join. This variation in hash probe performance is more significant when the hash join's hash table no longer fits into the CPU's L3 cache, but the result cache's hash table does. The apparent "random" access of hash buckets with each hash probe can cause a poor L3 cache hit ratio for large hash tables. Smaller hash tables generally perform better. The hash table used for the cache limits itself to not exceeding work_mem * hash_mem_multiplier in size. We maintain a dlist of keys for this cache and when we're adding new tuples and realize we've exceeded the memory budget, we evict cache entries starting with the least recently used ones until we have enough memory to add the new tuples to the cache. For parameterized nested loop joins, we now consider using one of these result cache nodes in between the nested loop node and its inner node. We determine when this might be useful based on cost, which is primarily driven off of what the expected cache hit ratio will be. Estimating the cache hit ratio relies on having good distinct estimates on the nested loop's parameters. For now, the planner will only consider using a result cache for parameterized nested loop joins. This works for both normal joins and also for LATERAL type joins to subqueries. It is possible to use this new node for other uses in the future. For example, to cache results from correlated subqueries. However, that's not done here due to some difficulties obtaining a distinct estimation on the outer plan to calculate the estimated cache hit ratio. Currently we plan the inner plan before planning the outer plan so there is no good way to know if a result cache would be useful or not since we can't estimate the number of times the subplan will be called until the outer plan is generated. The functionality being added here is newly introducing a dependency on the return value of estimate_num_groups() during the join search. Previously, during the join search, we only ever needed to perform selectivity estimations. With this commit, we need to use estimate_num_groups() in order to estimate what the hit ratio on the result cache will be. In simple terms, if we expect 10 distinct values and we expect 1000 outer rows, then we'll estimate the hit ratio to be 99%. Since cache hits are very cheap compared to scanning the underlying nodes on the inner side of the nested loop join, then this will significantly reduce the planner's cost for the join. However, it's fairly easy to see here that things will go bad when estimate_num_groups() incorrectly returns a value that's significantly lower than the actual number of distinct values. If this happens then that may cause us to make use of a nested loop join with a result cache instead of some other join type, such as a merge or hash join. Our distinct estimations have been known to be a source of trouble in the past, so the extra reliance on them here could cause the planner to choose slower plans than it did previous to having this feature. Distinct estimations are also fairly hard to estimate accurately when several tables have been joined already or when a WHERE clause filters out a set of values that are correlated to the expressions we're estimating the number of distinct value for. For now, the costing we perform during query planning for result caches does put quite a bit of faith in the distinct estimations being accurate. When these are accurate then we should generally see faster execution times for plans containing a result cache. However, in the real world, we may find that we need to either change the costings to put less trust in the distinct estimations being accurate or perhaps even disable this feature by default. There's always an element of risk when we teach the query planner to do new tricks that it decides to use that new trick at the wrong time and causes a regression. Users may opt to get the old behavior by turning the feature off using the enable_resultcache GUC. Currently, this is enabled by default. It remains to be seen if we'll maintain that setting for the release. Additionally, the name "Result Cache" is the best name I could think of for this new node at the time I started writing the patch. Nobody seems to strongly dislike the name. A few people did suggest other names but no other name seemed to dominate in the brief discussion that there was about names. Let's allow the beta period to see if the current name pleases enough people. If there's some consensus on a better name, then we can change it before the release. Please see the 2nd discussion link below for the discussion on the "Result Cache" name. Author: David Rowley Reviewed-by: Andy Fan, Justin Pryzby, Zhihong Yu Tested-By: Konstantin Knizhnik Discussion: https://postgr.es/m/CAApHDvrPcQyQdWERGYWx8J%2B2DLUNgXu%2BfOSbQ1UscxrunyXyrQ%40mail.gmail.com Discussion: https://postgr.es/m/CAApHDvq=yQXr5kqhRviT2RhNKwToaWr9JAN5t+5_PzhuRJ3wvg@mail.gmail.com	5 years ago
Etsuro Fujita	27e1f14563	Add support for asynchronous execution. ... This implements asynchronous execution, which runs multiple parts of a non-parallel-aware Append concurrently rather than serially to improve performance when possible. Currently, the only node type that can be run concurrently is a ForeignScan that is an immediate child of such an Append. In the case where such ForeignScans access data on different remote servers, this would run those ForeignScans concurrently, and overlap the remote operations to be performed simultaneously, so it'll improve the performance especially when the operations involve time-consuming ones such as remote join and remote aggregation. We may extend this to other node types such as joins or aggregates over ForeignScans in the future. This also adds the support for postgres_fdw, which is enabled by the table-level/server-level option "async_capable". The default is false. Robert Haas, Kyotaro Horiguchi, Thomas Munro, and myself. This commit is mostly based on the patch proposed by Robert Haas, but also uses stuff from the patch proposed by Kyotaro Horiguchi and from the patch proposed by Thomas Munro. Reviewed by Kyotaro Horiguchi, Konstantin Knizhnik, Andrey Lepikhov, Movead Li, Thomas Munro, Justin Pryzby, and others. Discussion: https://postgr.es/m/CA%2BTgmoaXQEt4tZ03FtQhnzeDEMzBck%2BLrni0UWHVVgOTnA6C1w%40mail.gmail.com Discussion: https://postgr.es/m/CA%2BhUKGLBRyu0rHrDCMC4%3DRn3252gogyp1SjOgG8SEKKZv%3DFwfQ%40mail.gmail.com Discussion: https://postgr.es/m/20200228.170650.667613673625155850.horikyota.ntt%40gmail.com	5 years ago
Stephen Frost	bbcc4eb2e0	Change checkpoint_completion_target default to 0.9 ... Common recommendations are that the checkpoint should be spread out as much as possible, provided we avoid having it take too long. This change updates the default to 0.9 (from 0.5) to match that recommendation. There was some debate about possibly removing the option entirely but it seems there may be some corner-cases where having it set much lower to try to force the checkpoint to be as fast as possible could result in fewer periods of time of reduced performance due to kernel flushing. General agreement is that the "spread more" is the preferred approach though and those who need to tune away from that value are much less common. Reviewed-By: Michael Paquier, Peter Eisentraut, Tom Lane, David Steele, Nathan Bossart Discussion: https://postgr.es/m/20201207175329.GM16415%40tamriel.snowman.net	5 years ago
Amit Kapila	26acb54a13	Revert "Enable parallel SELECT for "INSERT INTO ... SELECT ..."." ... To allow inserts in parallel-mode this feature has to ensure that all the constraints, triggers, etc. are parallel-safe for the partition hierarchy which is costly and we need to find a better way to do that. Additionally, we could have used existing cached information in some cases like indexes, domains, etc. to determine the parallel-safety. List of commits reverted, in reverse chronological order: ed62d3737c Doc: Update description for parallel insert reloption. c8f78b6161 Add a new GUC and a reloption to enable inserts in parallel-mode. c5be48f092 Improve FK trigger parallel-safety check added by 05c8482f7f. e2cda3c20a Fix use of relcache TriggerDesc field introduced by commit 05c8482f7f. e4e87a32cc Fix valgrind issue in commit 05c8482f7f. 05c8482f7f Enable parallel SELECT for "INSERT INTO ... SELECT ...". Discussion: https://postgr.es/m/E1lMiB9-0001c3-SY@gemulon.postgresql.org	5 years ago
Thomas Munro	61752afb26	Provide recovery_init_sync_method=syncfs. ... Since commit 2ce439f3 we have opened every file in the data directory and called fsync() at the start of crash recovery. This can be very slow if there are many files, leading to field complaints of systems taking minutes or even hours to begin crash recovery. Provide an alternative method, for Linux only, where we call syncfs() on every possibly different filesystem under the data directory. This is equivalent, but avoids faulting in potentially many inodes from potentially slow storage. The new mode comes with some caveats, described in the documentation, so the default value for the new setting is "fsync", preserving the older behavior. Reported-by: Michael Brown <michael.brown@discourse.org> Reviewed-by: Fujii Masao <masao.fujii@oss.nttdata.com> Reviewed-by: Paul Guo <guopa@vmware.com> Reviewed-by: Bruce Momjian <bruce@momjian.us> Reviewed-by: Justin Pryzby <pryzby@telsasoft.com> Reviewed-by: David Steele <david@pgmasters.net> Discussion: https://postgr.es/m/11bc2bb7-ecb5-3ad0-b39f-df632734cd81%40discourse.org Discussion: https://postgr.es/m/CAEET0ZHGnbXmi8yF3ywsDZvb3m9CbdsGZgfTXscQ6agcbzcZAw%40mail.gmail.com	5 years ago
Robert Haas	bbe0a81db6	Allow configurable LZ4 TOAST compression. ... There is now a per-column COMPRESSION option which can be set to pglz (the default, and the only option in up until now) or lz4. Or, if you like, you can set the new default_toast_compression GUC to lz4, and then that will be the default for new table columns for which no value is specified. We don't have lz4 support in the PostgreSQL code, so to use lz4 compression, PostgreSQL must be built --with-lz4. In general, TOAST compression means compression of individual column values, not the whole tuple, and those values can either be compressed inline within the tuple or compressed and then stored externally in the TOAST table, so those properties also apply to this feature. Prior to this commit, a TOAST pointer has two unused bits as part of the va_extsize field, and a compessed datum has two unused bits as part of the va_rawsize field. These bits are unused because the length of a varlena is limited to 1GB; we now use them to indicate the compression type that was used. This means we only have bit space for 2 more built-in compresison types, but we could work around that problem, if necessary, by introducing a new vartag_external value for any further types we end up wanting to add. Hopefully, it won't be too important to offer a wide selection of algorithms here, since each one we add not only takes more coding but also adds a build dependency for every packager. Nevertheless, it seems worth doing at least this much, because LZ4 gets better compression than PGLZ with less CPU usage. It's possible for LZ4-compressed datums to leak into composite type values stored on disk, just as it is for PGLZ. It's also possible for LZ4-compressed attributes to be copied into a different table via SQL commands such as CREATE TABLE AS or INSERT .. SELECT. It would be expensive to force such values to be decompressed, so PostgreSQL has never done so. For the same reasons, we also don't force recompression of already-compressed values even if the target table prefers a different compression method than was used for the source data. These architectural decisions are perhaps arguable but revisiting them is well beyond the scope of what seemed possible to do as part of this project. However, it's relatively cheap to recompress as part of VACUUM FULL or CLUSTER, so this commit adjusts those commands to do so, if the configured compression method of the table happens not to match what was used for some column value stored therein. Dilip Kumar. The original patches on which this work was based were written by Ildus Kurbangaliev, and those were patches were based on even earlier work by Nikita Glukhov, but the design has since changed very substantially, since allow a potentially large number of compression methods that could be added and dropped on a running system proved too problematic given some of the architectural issues mentioned above; the choice of which specific compression method to add first is now different; and a lot of the code has been heavily refactored. More recently, Justin Przyby helped quite a bit with testing and reviewing and this version also includes some code contributions from him. Other design input and review from Tomas Vondra, Álvaro Herrera, Andres Freund, Oleg Bartunov, Alexander Korotkov, and me. Discussion: http://postgr.es/m/20170907194236.4cefce96%40wp.localdomain Discussion: http://postgr.es/m/CAFiTN-uUpX3ck%3DK0mLEk-G_kUQY%3DSNOTeqdaNRR9FMdQrHKebw%40mail.gmail.com	5 years ago
Tomas Vondra	cd91de0d17	Remove temporary files after backend crash ... After a crash of a backend using temporary files, the files used to be left behind, on the basis that it might be useful for debugging. But we don't have any reports of anyone actually doing that, and it means the disk usage may grow over time due to repeated backend failures (possibly even hitting ENOSPC). So this behavior is a bit unfortunate, and fixing it required either manual cleanup (deleting files, which is error-prone) or restart of the instance (i.e. service disruption). This implements automatic cleanup of temporary files, controled by a new GUC remove_temp_files_after_crash. By default the files are removed, but it can be disabled to restore the old behavior if needed. Author: Euler Taveira Reviewed-by: Tomas Vondra, Michael Paquier, Anastasia Lubennikova, Thomas Munro Discussion: https://postgr.es/m/CAH503wDKdYzyq7U-QJqGn%3DGm6XmoK%2B6_6xTJ-Yn5WSvoHLY1Ww%40mail.gmail.com	5 years ago
Amit Kapila	c8f78b6161	Add a new GUC and a reloption to enable inserts in parallel-mode. ... Commit 05c8482f7f added the implementation of parallel SELECT for "INSERT INTO ... SELECT ..." which may incur non-negligible overhead in the additional parallel-safety checks that it performs, even when, in the end, those checks determine that parallelism can't be used. This is normally only ever a problem in the case of when the target table has a large number of partitions. A new GUC option "enable_parallel_insert" is added, to allow insert in parallel-mode. The default is on. In addition to the GUC option, the user may want a mechanism to allow inserts in parallel-mode with finer granularity at table level. The new table option "parallel_insert_enabled" allows this. The default is true. Author: "Hou, Zhijie" Reviewed-by: Greg Nancarrow, Amit Langote, Takayuki Tsunakawa, Amit Kapila Discussion: https://postgr.es/m/CAA4eK1K-cW7svLC2D7DHoGHxdAdg3P37BLgebqBOC2ZLc9a6QQ%40mail.gmail.com Discussion: https://postgr.es/m/CAJcOf-cXnB5cnMKqWEp2E2z7Mvcd04iLVmV=qpFJrR3AcrTS3g@mail.gmail.com	5 years ago
Peter Geoghegan	9f3665fbfc	Don't consider newly inserted tuples in nbtree VACUUM. ... Remove the entire idea of "stale stats" within nbtree VACUUM (stop caring about stats involving the number of inserted tuples). Also remove the vacuum_cleanup_index_scale_factor GUC/param on the master branch (though just disable them on postgres 13). The vacuum_cleanup_index_scale_factor/stats interface made the nbtree AM partially responsible for deciding when pg_class.reltuples stats needed to be updated. This seems contrary to the spirit of the index AM API, though -- it is not actually necessary for an index AM's bulk delete and cleanup callbacks to provide accurate stats when it happens to be inconvenient. The core code owns that. (Index AMs have the authority to perform or not perform certain kinds of deferred cleanup based on their own considerations, such as page deletion and recycling, but that has little to do with pg_class.reltuples/num_index_tuples.) This issue was fairly harmless until the introduction of the autovacuum_vacuum_insert_threshold feature by commit b07642db, which had an undesirable interaction with the vacuum_cleanup_index_scale_factor mechanism: it made insert-driven autovacuums perform full index scans, even though there is no real benefit to doing so. This has been tied to a regression with an append-only insert benchmark [1]. Also have remaining cases that perform a full scan of an index during a cleanup-only nbtree VACUUM indicate that the final tuple count is only an estimate. This prevents vacuumlazy.c from setting the index's pg_class.reltuples in those cases (it will now only update pg_class when vacuumlazy.c had TIDs for nbtree to bulk delete). This arguably fixes an oversight in deduplication-related bugfix commit 48e12913. [1] https://smalldatum.blogspot.com/2021/01/insert-benchmark-postgres-is-still.html Author: Peter Geoghegan <pg@bowt.ie> Reviewed-By: Masahiko Sawada <sawada.mshk@gmail.com> Discussion: https://postgr.es/m/CAD21AoA4WHthN5uU6+WScZ7+J_RcEjmcuH94qcoUPuB42ShXzg@mail.gmail.com Backpatch: 13-, where autovacuum_vacuum_insert_threshold was added.	5 years ago
Fujii Masao	ff99918c62	Track total amounts of times spent writing and syncing WAL data to disk. ... This commit adds new GUC track_wal_io_timing. When this is enabled, the total amounts of time XLogWrite writes and issue_xlog_fsync syncs WAL data to disk are counted in pg_stat_wal. This information would be useful to check how much WAL write and sync affect the performance. Enabling track_wal_io_timing will make the server query the operating system for the current time every time WAL is written or synced, which may cause significant overhead on some platforms. To avoid such additional overhead in the server with track_io_timing enabled, this commit introduces track_wal_io_timing as a separate parameter from track_io_timing. Note that WAL write and sync activity by walreceiver has not been tracked yet. This commit makes the server also track the numbers of times XLogWrite writes and issue_xlog_fsync syncs WAL data to disk, in pg_stat_wal, regardless of the setting of track_wal_io_timing. This counters can be used to calculate the WAL write and sync time per request, for example. Bump PGSTAT_FILE_FORMAT_ID. Bump catalog version. Author: Masahiro Ikeda Reviewed-By: Japin Li, Hayato Kuroda, Masahiko Sawada, David Johnston, Fujii Masao Discussion: https://postgr.es/m/0509ad67b585a5b86a83d445dfa75392@oss.nttdata.com	5 years ago
Peter Eisentraut	f5465fade9	Allow specifying CRL directory ... Add another method to specify CRLs, hashed directory method, for both server and client side. This offers a means for server or libpq to load only CRLs that are required to verify a certificate. The CRL directory is specifed by separate GUC variables or connection options ssl_crl_dir and sslcrldir, alongside the existing ssl_crl_file and sslcrl, so both methods can be used at the same time. Author: Kyotaro Horiguchi <horikyota.ntt@gmail.com> Discussion: https://www.postgresql.org/message-id/flat/20200731.173911.904649928639357911.horikyota.ntt@gmail.com	5 years ago