185 Commits (b14e9ce7d55c75ffa160b07765eb9dffde70b5fa)

Author	SHA1	Message	Date
Michael Paquier	b14e9ce7d5	Extend PgStat_HashKey.objid from 4 to 8 bytes ... This opens the possibility to define keys for more types of statistics kinds in PgStat_HashKey, the first case being 8-byte query IDs for statistics like pg_stat_statements. This increases the size of PgStat_HashKey from 12 to 16 bytes, while PgStatShared_HashEntry, entry stored in the dshash for pgstats, keeps the same size due to alignment. xl_xact_stats_item, that tracks the stats items to drop in commit WAL records, is increased from 12 to 16 bytes. Note that individual chunks in commit WAL records should be multiples of sizeof(int), hence 8-byte object IDs are stored as two uint32, based on a suggestion from Heikki Linnakangas. While on it, the field of PgStat_HashKey is renamed from "objoid" to "objid", as for some stats kinds this field does not refer to OIDs but just IDs, like for replication slot stats. This commit bumps the following format variables: - PGSTAT_FILE_FORMAT_ID, as PgStat_HashKey is written to the stats file for non-serialized stats kinds in the dshash table. - XLOG_PAGE_MAGIC for the changes in xl_xact_stats_item. - Catalog version, for the SQL function pg_stat_have_stats(). Reviewed-by: Bertrand Drouvot Discussion: https://postgr.es/m/ZsvTS9EW79Up8I62@paquier.xyz	1 year ago
Peter Eisentraut	2b5f57977f	Add const qualifiers to XLogRegister*() functions ... Add const qualifiers to XLogRegisterData() and XLogRegisterBufData(). Several unconstify() calls can be removed. Reviewed-by: Aleksander Alekseev <aleksander@timescale.com> Discussion: https://www.postgresql.org/message-id/dd889784-9ce7-436a-b4f1-52e4a5e577bd@eisentraut.org	1 year ago
Robert Haas	402b586d0a	Do not summarize WAL if generated with wal_level=minimal. ... To do this, we must include the wal_level in the first WAL record covered by each summary file; so add wal_level to struct Checkpoint and the payload of XLOG_CHECKPOINT_REDO and XLOG_END_OF_RECOVERY. This, in turn, requires bumping XLOG_PAGE_MAGIC and, since the Checkpoint is also stored in the control file, also PG_CONTROL_VERSION. It's not great to do that so late in the release cycle, but the alternative seems to ship v17 without robust protections against this scenario, which could result in corrupted incremental backups. A side effect of this patch is that, when a server with wal_level=replica is started with summarize_wal=on for the first time, summarization will no longer begin with the oldest WAL that still exists in pg_wal, but rather from the first checkpoint after that. This change should be harmless, because a WAL summary for a partial checkpoint cycle can never make an incremental backup possible when it would otherwise not have been. Report by Fujii Masao. Patch by me. Review and/or testing by Jakub Wartak and Fujii Masao. Discussion: http://postgr.es/m/6e30082e-041b-4e31-9633-95a66de76f5d@oss.nttdata.com	1 year ago
Heikki Linnakangas	f83d709760	Merge prune, freeze and vacuum WAL record formats ... The new combined WAL record is now used for pruning, freezing and 2nd pass of vacuum. This is in preparation for changing VACUUM to write a combined prune+freeze record per page, instead of separate two records. The new WAL record format now supports that, but the code still always writes separate records for pruning and freezing. This reserves separate XLOG_HEAP2_* info codes for when the pruning record is emitted for on-access pruning or VACUUM, per Peter Geoghegan's suggestion. The record format is identical, but having separate info codes makes it easier analyze pruning and vacuuming with pg_waldump. The function to emit the new WAL record, log_heap_prune_and_freeze(), is in pruneheap.c. The existing heap_log_freeze_plan() and its subroutines are moved to pruneheap.c without changes, to keep them together with log_heap_prune_and_freeze(). Author: Melanie Plageman <melanieplageman@gmail.com> Discussion: https://www.postgresql.org/message-id/CAAKRu_azf-zH%3DDgVbquZ3tFWjMY1w5pO8m-TXJaMdri8z3933g@mail.gmail.com Discussion: https://www.postgresql.org/message-id/CAAKRu_b2oE4GL%3Dq4g9mcByS9yT7wTQvEH9OLpabj28e%2BWKFi2A@mail.gmail.com	2 years ago
Bruce Momjian	29275b1d17	Update copyright for 2024 ... Reported-by: Michael Paquier Discussion: https://postgr.es/m/ZZKTDPxBBMt3C0J9@paquier.xyz Backpatch-through: 12	2 years ago
Peter Eisentraut	611806cd72	Add trailing commas to enum definitions ... Since C99, there can be a trailing comma after the last value in an enum definition. A lot of new code has been introducing this style on the fly. Some new patches are now taking an inconsistent approach to this. Some add the last comma on the fly if they add a new last value, some are trying to preserve the existing style in each place, some are even dropping the last comma if there was one. We could nudge this all in a consistent direction if we just add the trailing commas everywhere once. I omitted a few places where there was a fixed "last" value that will always stay last. I also skipped the header files of libpq and ecpg, in case people want to use those with older compilers. There were also a small number of cases where the enum type wasn't used anywhere (but the enum values were), which ended up confusing pgindent a bit, so I left those alone. Discussion: https://www.postgresql.org/message-id/flat/386f8c45-c8ac-4681-8add-e3b0852c1620%40eisentraut.org	2 years ago
Robert Haas	afd12774ae	During online checkpoints, insert XLOG_CHECKPOINT_REDO at redo point. ... This allows tools that read the WAL sequentially to identify (possible) redo points when they're reached, rather than only being able to detect them in retrospect when XLOG_CHECKPOINT_ONLINE is found, possibly much later in the WAL stream. There are other possible applications as well; see the discussion links below. Any redo location that precedes the checkpoint location should now point to an XLOG_CHECKPOINT_REDO record, so add a cross-check to verify this. While adjusting the code in CreateCheckPoint() for this patch, I made it call WALInsertLockAcquireExclusive a bit later than before, since there appears to be no need for it to be held while checking whether the system is idle, whether this is an end-of-recovery checkpoint, or what the current timeline is. Bump XLOG_PAGE_MAGIC. Patch by me, based in part on earlier work from Dilip Kumar. Review by Dilip Kumar, Amit Kapila, Andres Freund, and Michael Paquier. Discussion: http://postgr.es/m/CA+TgmoYy-Vc6G9QKcAKNksCa29cv__czr+N9X_QCxEfQVpp_8w@mail.gmail.com Discussion: http://postgr.es/m/20230614194717.jyuw3okxup4cvtbt%40awork3.anarazel.de Discussion: http://postgr.es/m/CA+hUKG+b2ego8=YNW2Ohe9QmSiReh1-ogrv8V_WZpJTqP3O+2w@mail.gmail.com	2 years ago
Andres Freund	6af1793954	Add info in WAL records in preparation for logical slot conflict handling ... This commit only implements one prerequisite part for allowing logical decoding. The commit message contains an explanation of the overall design, which later commits will refer back to. Overall design: 1. We want to enable logical decoding on standbys, but replay of WAL from the primary might remove data that is needed by logical decoding, causing error(s) on the standby. To prevent those errors, a new replication conflict scenario needs to be addressed (as much as hot standby does). 2. Our chosen strategy for dealing with this type of replication slot is to invalidate logical slots for which needed data has been removed. 3. To do this we need the latestRemovedXid for each change, just as we do for physical replication conflicts, but we also need to know whether any particular change was to data that logical replication might access. That way, during WAL replay, we know when there is a risk of conflict and, if so, if there is a conflict. 4. We can't rely on the standby's relcache entries for this purpose in any way, because the startup process can't access catalog contents. 5. Therefore every WAL record that potentially removes data from the index or heap must carry a flag indicating whether or not it is one that might be accessed during logical decoding. Why do we need this for logical decoding on standby? First, let's forget about logical decoding on standby and recall that on a primary database, any catalog rows that may be needed by a logical decoding replication slot are not removed. This is done thanks to the catalog_xmin associated with the logical replication slot. But, with logical decoding on standby, in the following cases: - hot_standby_feedback is off - hot_standby_feedback is on but there is no a physical slot between the primary and the standby. Then, hot_standby_feedback will work, but only while the connection is alive (for example a node restart would break it) Then, the primary may delete system catalog rows that could be needed by the logical decoding on the standby (as it does not know about the catalog_xmin on the standby). So, it’s mandatory to identify those rows and invalidate the slots that may need them if any. Identifying those rows is the purpose of this commit. Implementation: When a WAL replay on standby indicates that a catalog table tuple is to be deleted by an xid that is greater than a logical slot's catalog_xmin, then that means the slot's catalog_xmin conflicts with the xid, and we need to handle the conflict. While subsequent commits will do the actual conflict handling, this commit adds a new field isCatalogRel in such WAL records (and a new bit set in the xl_heap_visible flags field), that is true for catalog tables, so as to arrange for conflict handling. The affected WAL records are the ones that already contain the snapshotConflictHorizon field, namely: - gistxlogDelete - gistxlogPageReuse - xl_hash_vacuum_one_page - xl_heap_prune - xl_heap_freeze_page - xl_heap_visible - xl_btree_reuse_page - xl_btree_delete - spgxlogVacuumRedirect Due to this new field being added, xl_hash_vacuum_one_page and gistxlogDelete do now contain the offsets to be deleted as a FLEXIBLE_ARRAY_MEMBER. This is needed to ensure correct alignment. It's not needed on the others struct where isCatalogRel has been added. This commit just introduces the WAL format changes mentioned above. Handling the actual conflicts will follow in future commits. Bumps XLOG_PAGE_MAGIC as the several WAL records are changed. Author: "Drouvot, Bertrand" <bertranddrouvot.pg@gmail.com> Author: Andres Freund <andres@anarazel.de> (in an older version) Author: Amit Khandekar <amitdkhan.pg@gmail.com> (in an older version) Reviewed-by: "Drouvot, Bertrand" <bertranddrouvot.pg@gmail.com> Reviewed-by: Andres Freund <andres@anarazel.de> Reviewed-by: Robert Haas <robertmhaas@gmail.com> Reviewed-by: Fabrízio de Royes Mello <fabriziomello@gmail.com> Reviewed-by: Melanie Plageman <melanieplageman@gmail.com>	3 years ago
Amit Kapila	a6cd1fc692	Change xl_hash_vacuum_one_page.ntuples from int to uint16. ... This will create two bytes of padding space in xl_hash_vacuum_one_page which can be used for future patches. This makes the datatype of xl_hash_vacuum_one_page.ntuples same as gistxlogDelete.ntodelete which is advisable as both are used for the same purpose. Author: Bertrand Drouvot Reviewed-by: Nathan Bossart Discussion: https://postgr.es/m/b0e20c40-cb7a-fc1c-c607-2a78dac5021e@gmail.com	3 years ago
Bruce Momjian	c8e1ba736b	Update copyright for 2023 ... Backpatch-through: 11	3 years ago
Jeff Davis	1eda3ce802	Mark argument of RegisterCustomRmgr() as const.	3 years ago
Peter Geoghegan	9e5405993c	Deduplicate freeze plans in freeze WAL records. ... Make heapam WAL records that describe freezing performed by VACUUM more space efficient by storing each distinct "freeze plan" once, alongside an array of associated page offset numbers (one per freeze plan). The freeze plans required for most heap pages tend to naturally have a great deal of redundancy, so this technique is very effective in practice. It often leads to freeze WAL records that are less than 20% of the size of equivalent WAL records generated using the previous approach. The freeze plan concept was introduced by commit 3b97e6823b, which fixed bugs in VACUUM's handling of MultiXacts. We retain the concept of freeze plans, but go back to using page offset number arrays. There is no loss of generality here because deduplication is an additive process that gets applied mechanically when FREEZE_PAGE WAL records are built. More than anything else, freeze plan deduplication is an optimization that reduces the marginal cost of freezing additional tuples on pages that will need to have at least one or two tuples frozen in any case. Ongoing work that adds page-level freezing to VACUUM will take full advantage of the improved cost profile through batching. Also refactor some of the details surrounding recovery conflicts needed to REDO freeze records in passing: make original execution responsible for generating a standard latestRemovedXid cutoff, rather than working backwards to get the same cutoff in the REDO routine. Bugfix commit 66fbcb0d2e did it the other way around, which is equivalent but obscures what's going on. Also rename the cutoff field from the WAL record/struct (rename the field cutoff_xid to latestRemovedXid to match similar WAL records). Processing of conflicts by REDO routines is already completely uniform, so tools like pg_waldump should present the information driving the process uniformly. There are two remaining WAL record types that still don't quite follow this convention (heapam's VISIBLE record type and SP-GiST's VACUUM_REDIRECT record type). They can be brought into line by later work that totally standardizes how the cutoffs are presented. Bump XLOG_PAGE_MAGIC. Author: Peter Geoghegan <pg@bowt.ie> Reviewed-By: Masahiko Sawada <sawada.mshk@gmail.com> Reviewed-By: Nathan Bossart <nathandbossart@gmail.com> Reviewed-By: Justin Pryzby <pryzby@telsasoft.com> Discussion: https://postgr.es/m/CAH2-Wz=XytErMnb8FAyFd+OQEbiipB0Q2FmFdXrggPL4VBnRYQ@mail.gmail.com	3 years ago
Peter Eisentraut	507ba16b28	Convert macros to static inline functions (xlog_internal.h) ... Reviewed-by: Amul Sul <sulamul@gmail.com> Discussion: https://www.postgresql.org/message-id/flat/5b558da8-99fb-0a99-83dd-f72f05388517%40enterprisedb.com	3 years ago
Robert Haas	b0a55e4329	Change internal RelFileNode references to RelFileNumber or RelFileLocator. ... We have been using the term RelFileNode to refer to either (1) the integer that is used to name the sequence of files for a certain relation within the directory set aside for that tablespace/database combination; or (2) that value plus the OIDs of the tablespace and database; or occasionally (3) the whole series of files created for a relation based on those values. Using the same name for more than one thing is confusing. Replace RelFileNode with RelFileNumber when we're talking about just the single number, i.e. (1) from above, and with RelFileLocator when we're talking about all the things that are needed to locate a relation's files on disk, i.e. (2) from above. In the places where we refer to (3) as a relfilenode, instead refer to "relation storage". Since there is a ton of SQL code in the world that knows about pg_class.relfilenode, don't change the name of that column, or of other SQL-facing things that derive their name from it. On the other hand, do adjust closely-related internal terminology. For example, the structure member names dbNode and spcNode appear to be derived from the fact that the structure itself was called RelFileNode, so change those to dbOid and spcOid. Likewise, various variables with names like rnode and relnode get renamed appropriately, according to how they're being used in context. Hopefully, this is clearer than before. It is also preparation for future patches that intend to widen the relfilenumber fields from its current width of 32 bits. Variables that store a relfilenumber are now declared as type RelFileNumber rather than type Oid; right now, these are the same, but that can now more easily be changed. Dilip Kumar, per an idea from me. Reviewed also by Andres Freund. I fixed some whitespace issues, changed a couple of words in a comment, and made one other minor correction. Discussion: http://postgr.es/m/CA+TgmoamOtXbVAQf9hWFzonUo6bhhjS6toZQd7HZ-pmojtAmag@mail.gmail.com Discussion: http://postgr.es/m/CA+Tgmobp7+7kmi4gkq7Y+4AM9fTvL+O1oQ4-5gFTT+6Ng-dQ=g@mail.gmail.com Discussion: http://postgr.es/m/CAFiTN-vTe79M8uDH1yprOU64MNFE+R3ODRuA+JWf27JbhY4hJw@mail.gmail.com	4 years ago
Robert Haas	8ec569479f	Apply PGDLLIMPORT markings broadly. ... Up until now, we've had a policy of only marking certain variables in the PostgreSQL header files with PGDLLIMPORT, but now we've decided to mark them all. This means that extensions running on Windows should no longer operate at a disadvantage as compared to extensions running on Linux: if the variable is present in a header file, it should be accessible. Discussion: http://postgr.es/m/CA+TgmoYanc1_FSfimhgiWSqVyP5KKmh5NP2BWNwDhO8Pg2vGYQ@mail.gmail.com	4 years ago
Jeff Davis	2258e76f90	Add contrib/pg_walinspect. ... Provides similar functionality to pg_waldump, but from a SQL interface rather than a separate utility. Author: Bharath Rupireddy Reviewed-by: Greg Stark, Kyotaro Horiguchi, Andres Freund, Ashutosh Sharma, Nitin Jadhav, RKN Sai Krishna Discussion: https://postgr.es/m/CALj2ACUGUYXsEQdKhEdsBzhGEyF3xggvLdD8C0VT72TNEfOiog%40mail.gmail.com	4 years ago
Jeff Davis	957aa4d87a	Fix another buildfarm issue from commit 5c279a6d35. ... Discussion: https://postgr.es/m/3280724.1649340315@sss.pgh.pa.us	4 years ago
Jeff Davis	5c279a6d35	Custom WAL Resource Managers. ... Allow extensions to specify a new custom resource manager (rmgr), which allows specialized WAL. This is meant to be used by a Table Access Method or Index Access Method. Prior to this commit, only Generic WAL was available, which offers support for recovery and physical replication but not logical replication. Reviewed-by: Julien Rouhaud, Bharath Rupireddy, Andres Freund Discussion: https://postgr.es/m/ed1fb2e22d15d3563ae0eb610f7b61bb15999c0a.camel%40j-davis.com	4 years ago
Andres Freund	8b1dccd37c	pgstat: scaffolding for transactional stats creation / drop. ... One problematic part of the current statistics collector design is that there is no reliable way of getting rid of statistics entries. Because of that pgstat_vacuum_stat() (called by [auto-]vacuum) matches all stats for the current database with the catalog contents and tries to drop now-superfluous entries. That's quite expensive. What's worse, it doesn't work on physical replicas, despite physical replicas collection statistics entries. This commit introduces infrastructure to create / drop statistics entries transactionally, together with the underlying catalog objects (functions, relations, subscriptions). pgstat_xact.c maintains a list of stats entries created / dropped transactionally in the current transaction. To ensure the removal of statistics entries is durable dropped statistics entries are included in commit / abort (and prepare) records, which also ensures that stats entries are dropped on standbys. Statistics entries created separately from creating the underlying catalog object (e.g. when stats were previously lost due to an immediate restart) are *not* WAL logged. However that can only happen outside of the transaction creating the catalog object, so it does not lead to "leaked" statistics entries. For this to work, functions creating / dropping functions / relations / subscriptions need to call into pgstat. For subscriptions this was already done when dropping subscriptions, via pgstat_report_subscription_drop() (now renamed to pgstat_drop_subscription()). This commit does not actually drop stats yet, it just provides the infrastructure. It is however a largely independent piece of infrastructure, so committing it separately makes sense. Bumps XLOG_PAGE_MAGIC. Author: Andres Freund <andres@anarazel.de> Reviewed-By: Thomas Munro <thomas.munro@gmail.com> Reviewed-By: Kyotaro Horiguchi <horikyota.ntt@gmail.com> Discussion: https://postgr.es/m/20220303021600.hs34ghqcw6zcokdh@alap3.anarazel.de	4 years ago
Michael Paquier	8e375ea4a0	Bump XLOG_PAGE_MAGIC due to the addition of wal_compression=zstd ... While on it, fix a thinko in the docs, introduced by the same commit. Oversights in e953732. Reported-by: Justin Pryzby Discussion: https://postgr.es/m/20220311214900.GN28503@telsasoft.com	4 years ago
Jeff Davis	7a5f6b4748	Make logical decoding a part of the rmgr. ... Add a new rmgr method, rm_decode, and use that rather than a switch statement. In preparation for rmgr extensibility. Reviewed-by: Julien Rouhaud Discussion: https://postgr.es/m/ed1fb2e22d15d3563ae0eb610f7b61bb15999c0a.camel%40j-davis.com Discussion: https://postgr.es/m/20220118095332.6xtlcjoyxobv6cbk@jrouhaud	4 years ago
Bruce Momjian	27b77ecf9f	Update copyright for 2022 ... Backpatch-through: 10	4 years ago
Alvaro Herrera	ff9f111bce	Fix WAL replay in presence of an incomplete record ... Physical replication always ships WAL segment files to replicas once they are complete. This is a problem if one WAL record is split across a segment boundary and the primary server crashes before writing down the segment with the next portion of the WAL record: WAL writing after crash recovery would happily resume at the point where the broken record started, overwriting that record ... but any standby or backup may have already received a copy of that segment, and they are not rewinding. This causes standbys to stop following the primary after the latter crashes: LOG: invalid contrecord length 7262 at A8/D9FFFBC8 because the standby is still trying to read the continuation record (contrecord) for the original long WAL record, but it is not there and it will never be. A workaround is to stop the replica, delete the WAL file, and restart it -- at which point a fresh copy is brought over from the primary. But that's pretty labor intensive, and I bet many users would just give up and re-clone the standby instead. A fix for this problem was already attempted in commit 515e3d84a0, but it only addressed the case for the scenario of WAL archiving, so streaming replication would still be a problem (as well as other things such as taking a filesystem-level backup while the server is down after having crashed), and it had performance scalability problems too; so it had to be reverted. This commit fixes the problem using an approach suggested by Andres Freund, whereby the initial portion(s) of the split-up WAL record are kept, and a special type of WAL record is written where the contrecord was lost, so that WAL replay in the replica knows to skip the broken parts. With this approach, we can continue to stream/archive segment files as soon as they are complete, and replay of the broken records will proceed across the crash point without a hitch. Because a new type of WAL record is added, users should be careful to upgrade standbys first, primaries later. Otherwise they risk the standby being unable to start if the primary happens to write such a record. A new TAP test that exercises this is added, but the portability of it is yet to be seen. This has been wrong since the introduction of physical replication, so backpatch all the way back. In stable branches, keep the new XLogReaderState members at the end of the struct, to avoid an ABI break. Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com> Reviewed-by: Nathan Bossart <bossartn@amazon.com> Discussion: https://postgr.es/m/202108232252.dh7uxf6oxwcy@alvherre.pgsql	4 years ago
Michael Paquier	445e36ad4e	Bump XLOG_PAGE_MAGIC for format changes related to FPW compression ... Oversight in 4035cd5, spotted by Tom Lane. Discussion: https://postgr.es/m/365778.1624941613@sss.pgh.pa.us	5 years ago
Fujii Masao	08aa89b326	Remove COMMIT_TS_SETTS record. ... Commit 438fc4a39c prevented the WAL replay from writing COMMIT_TS_SETTS record. By this change there is no code that generates COMMIT_TS_SETTS record in PostgreSQL core. Also we can think that there are no extensions using the record because we've not received so far any complaints about the issue that commit 438fc4a39c fixed. Therefore this commit removes COMMIT_TS_SETTS record and its related code. Even without this record, the timestamp required for commit timestamp feature can be acquired from the COMMIT record. Bump WAL page magic. Reported-by: lx zou <zoulx1982@163.com> Author: Fujii Masao Reviewed-by: Alvaro Herrera Discussion: https://postgr.es/m/16931-620d0f2fdc6108f1@postgresql.org	5 years ago
Peter Geoghegan	8523492d4e	Remove tupgone special case from vacuumlazy.c. ... Retry the call to heap_prune_page() in rare cases where there is disagreement between the heap_prune_page() call and the call to HeapTupleSatisfiesVacuum() that immediately follows. Disagreement is possible when a concurrently-aborted transaction makes a tuple DEAD during the tiny window between each step. This was the only case where a tuple considered DEAD by VACUUM still had storage following pruning. VACUUM's definition of dead tuples is now uniformly simple and unambiguous: dead tuples from each page are always LP_DEAD line pointers that were encountered just after we performed pruning (and just before we considered freezing remaining items with tuple storage). Eliminating the tupgone=true special case enables INDEX_CLEANUP=off style skipping of index vacuuming that takes place based on flexible, dynamic criteria. The INDEX_CLEANUP=off case had to know about skipping indexes up-front before now, due to a subtle interaction with the special case (see commit dd695979) -- this was a special case unto itself. Now there are no special cases. And so now it won't matter when or how we decide to skip index vacuuming: it won't affect how pruning behaves, and it won't be affected by any of the implementation details of pruning or freezing. Also remove XLOG_HEAP2_CLEANUP_INFO records. These are no longer necessary because we now rely entirely on heap pruning taking care of recovery conflicts. There is no longer any need to generate recovery conflicts for DEAD tuples that pruning just missed. This also means that heap vacuuming now uses exactly the same strategy for recovery conflicts as index vacuuming always has: REDO routines never need to process a latestRemovedXid from the WAL record, since earlier REDO of the WAL record from pruning is sufficient in all cases. The generic XLOG_HEAP2_CLEAN record type is now split into two new record types to reflect this new division (these are called XLOG_HEAP2_PRUNE and XLOG_HEAP2_VACUUM). Also stop acquiring a super-exclusive lock for heap pages when they're vacuumed during VACUUM's second heap pass. A regular exclusive lock is enough. This is correct because heap page vacuuming is now strictly a matter of setting the LP_DEAD line pointers to LP_UNUSED. No other backend can have a pointer to a tuple located in a pinned buffer that can be invalidated by a concurrent heap page vacuum operation. Heap vacuuming can now be thought of as conceptually similar to index vacuuming and conceptually dissimilar to heap pruning. Heap pruning now has sole responsibility for anything involving the logical contents of the database (e.g., managing transaction status information, recovery conflicts, considering what to do with HOT chains). Index vacuuming and heap vacuuming are now only concerned with recycling garbage items from physical data structures that back the logical database. Bump XLOG_PAGE_MAGIC due to pruning and heap page vacuum WAL record changes. Credit for the idea of retrying pruning a page to avoid the tupgone case goes to Andres Freund. Author: Peter Geoghegan <pg@bowt.ie> Reviewed-By: Andres Freund <andres@anarazel.de> Reviewed-By: Masahiko Sawada <sawada.mshk@gmail.com> Discussion: https://postgr.es/m/CAH2-WznneCXTzuFmcwx_EyRQgfsfJAAsu+CsqRFmFXCAar=nJw@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
Peter Geoghegan	e5d8a99903	Use full 64-bit XIDs in deleted nbtree pages. ... Otherwise we risk "leaking" deleted pages by making them non-recyclable indefinitely. Commit 6655a729 did the same thing for deleted pages in GiST indexes. That work was used as a starting point here. Stop storing an XID indicating the oldest bpto.xact across all deleted though unrecycled pages in nbtree metapages. There is no longer any reason to care about that condition/the oldest XID. It only ever made sense when wraparound was something _bt_vacuum_needs_cleanup() had to consider. The btm_oldest_btpo_xact metapage field has been repurposed and renamed. It is now btm_last_cleanup_num_delpages, which is used to remember how many non-recycled deleted pages remain from the last VACUUM (in practice its value is usually the precise number of pages that were _newly deleted_ during the specific VACUUM operation that last set the field). The general idea behind storing btm_last_cleanup_num_delpages is to use it to give _some_ consideration to non-recycled deleted pages inside _bt_vacuum_needs_cleanup() -- though never too much. We only really need to avoid leaving a truly excessive number of deleted pages in an unrecycled state forever. We only do this to cover certain narrow cases where no other factor makes VACUUM do a full scan, and yet the index continues to grow (and so actually misses out on recycling existing deleted pages). These metapage changes result in a clear user-visible benefit: We no longer trigger full index scans during VACUUM operations solely due to the presence of only 1 or 2 known deleted (though unrecycled) blocks from a very large index. All that matters now is keeping the costs and benefits in balance over time. Fix an issue that has been around since commit 857f9c36, which added the "skip full scan of index" mechanism (i.e. the _bt_vacuum_needs_cleanup() logic). The accuracy of btm_last_cleanup_num_heap_tuples accidentally hinged upon _when_ the source value gets stored. We now always store btm_last_cleanup_num_heap_tuples in btvacuumcleanup(). This fixes the issue because IndexVacuumInfo.num_heap_tuples (the source field) is expected to accurately indicate the state of the table _after_ the VACUUM completes inside btvacuumcleanup(). A backpatchable fix cannot easily be extracted from this commit. A targeted fix for the issue will follow in a later commit, though that won't happen today. I (pgeoghegan) have chosen to remove any mention of deleted pages in the documentation of the vacuum_cleanup_index_scale_factor GUC/param, since the presence of deleted (though unrecycled) pages is no longer of much concern to users. The vacuum_cleanup_index_scale_factor description in the docs now seems rather unclear in any case, and it should probably be rewritten in the near future. Perhaps some passing mention of page deletion will be added back at the same time. Bump XLOG_PAGE_MAGIC due to nbtree WAL records using full XIDs now. Author: Peter Geoghegan <pg@bowt.ie> Reviewed-By: Masahiko Sawada <sawada.mshk@gmail.com> Discussion: https://postgr.es/m/CAH2-WznpdHvujGUwYZ8sihX=d5u-tRYhi-F4wnV2uN2zHpMUXw@mail.gmail.com	5 years ago
Peter Geoghegan	d168b66682	Enhance nbtree index tuple deletion. ... Teach nbtree and heapam to cooperate in order to eagerly remove duplicate tuples representing dead MVCC versions. This is "bottom-up deletion". Each bottom-up deletion pass is triggered lazily in response to a flood of versions on an nbtree leaf page. This usually involves a "logically unchanged index" hint (these are produced by the executor mechanism added by commit 9dc718bd). The immediate goal of bottom-up index deletion is to avoid "unnecessary" page splits caused entirely by version duplicates. It naturally has an even more useful effect, though: it acts as a backstop against accumulating an excessive number of index tuple versions for any given _logical row_. Bottom-up index deletion complements what we might now call "top-down index deletion": index vacuuming performed by VACUUM. Bottom-up index deletion responds to the immediate local needs of queries, while leaving it up to autovacuum to perform infrequent clean sweeps of the index. The overall effect is to avoid certain pathological performance issues related to "version churn" from UPDATEs. The previous tableam interface used by index AMs to perform tuple deletion (the table_compute_xid_horizon_for_tuples() function) has been replaced with a new interface that supports certain new requirements. Many (perhaps all) of the capabilities added to nbtree by this commit could also be extended to other index AMs. That is left as work for a later commit. Extend deletion of LP_DEAD-marked index tuples in nbtree by adding logic to consider extra index tuples (that are not LP_DEAD-marked) for deletion in passing. This increases the number of index tuples deleted significantly in many cases. The LP_DEAD deletion process (which is now called "simple deletion" to clearly distinguish it from bottom-up deletion) won't usually need to visit any extra table blocks to check these extra tuples. We have to visit the same table blocks anyway to generate a latestRemovedXid value (at least in the common case where the index deletion operation's WAL record needs such a value). Testing has shown that the "extra tuples" simple deletion enhancement increases the number of index tuples deleted with almost any workload that has LP_DEAD bits set in leaf pages. That is, it almost never fails to delete at least a few extra index tuples. It helps most of all in cases that happen to naturally have a lot of delete-safe tuples. It's not uncommon for an individual deletion operation to end up deleting an order of magnitude more index tuples compared to the old naive approach (e.g., custom instrumentation of the patch shows that this happens fairly often when the regression tests are run). Add a further enhancement that augments simple deletion and bottom-up deletion in indexes that make use of deduplication: Teach nbtree's _bt_delitems_delete() function to support granular TID deletion in posting list tuples. It is now possible to delete individual TIDs from posting list tuples provided the TIDs have a tableam block number of a table block that gets visited as part of the deletion process (visiting the table block can be triggered directly or indirectly). Setting the LP_DEAD bit of a posting list tuple is still an all-or-nothing thing, but that matters much less now that deletion only needs to start out with the right _general_ idea about which index tuples are deletable. Bump XLOG_PAGE_MAGIC because xl_btree_delete changed. No bump in BTREE_VERSION, since there are no changes to the on-disk representation of nbtree indexes. Indexes built on PostgreSQL 12 or PostgreSQL 13 will automatically benefit from bottom-up index deletion (i.e. no reindexing required) following a pg_upgrade. The enhancement to simple deletion is available with all B-Tree indexes following a pg_upgrade, no matter what PostgreSQL version the user upgrades from. Author: Peter Geoghegan <pg@bowt.ie> Reviewed-By: Heikki Linnakangas <hlinnaka@iki.fi> Reviewed-By: Victor Yegorov <vyegorov@gmail.com> Discussion: https://postgr.es/m/CAH2-Wzm+maE3apHB8NOtmM=p-DO65j2V5GzAWCOEEuy3JZgb2g@mail.gmail.com	5 years ago
Bruce Momjian	ca3b37487b	Update copyright for 2021 ... Backpatch-through: 9.5	5 years ago
Noah Misch	676a9c3cc4	Correct several behavior descriptions in comments. ... Reuse cautionary language from src/test/ssl/README in src/test/kerberos/README. SLRUs have had access to six-character segments names since commit 73c986adde, and recovery stopped calling HeapTupleHeaderAdvanceLatestRemovedXid() in commit 558a9165e0. The other corrections are more self-evident.	5 years ago
Amit Kapila	c55040ccd0	WAL Log invalidations at command end with wal_level=logical. ... When wal_level=logical, write invalidations at command end into WAL so that decoding can use this information. This patch is required to allow the streaming of in-progress transactions in logical decoding.  The actual work to allow streaming will be committed as a separate patch. We still add the invalidations to the cache and write them to WAL at commit time in RecordTransactionCommit(). This uses the existing XLOG_INVALIDATIONS xlog record type, from the RM_STANDBY_ID resource manager (see LogStandbyInvalidations for details). So existing code relying on those invalidations (e.g. redo) does not need to be changed. The invalidations written at command end uses a new xlog record type XLOG_XACT_INVALIDATIONS, from RM_XACT_ID resource manager. See LogLogicalInvalidations for details. These new xlog records are ignored by existing redo procedures, which still rely on the invalidations written to commit records. The invalidations are decoded and accumulated in top-transaction, and then executed during replay.  This obviates the need to decode the invalidations as part of a commit record. Bump XLOG_PAGE_MAGIC, since this introduces XLOG_XACT_INVALIDATIONS. Author: Dilip Kumar, Tomas Vondra, Amit Kapila Reviewed-by: Amit Kapila Tested-by: Neha Sharma and Mahendra Singh Thalor Discussion: https://postgr.es/m/688b0b7f-2f6c-d827-c27b-216a8e3ea700@2ndquadrant.com	5 years ago
Amit Kapila	0bead9af48	Immediately WAL-log subtransaction and top-level XID association. ... The logical decoding infrastructure needs to know which top-level transaction the subxact belongs to, in order to decode all the changes. Until now that might be delayed until commit, due to the caching (GPROC_MAX_CACHED_SUBXIDS), preventing features requiring incremental decoding. So we also write the assignment info into WAL immediately, as part of the next WAL record (to minimize overhead) only when wal_level=logical. We can not remove the existing XLOG_XACT_ASSIGNMENT WAL as that is required for avoiding overflow in the hot standby snapshot. Bump XLOG_PAGE_MAGIC, since this introduces XLR_BLOCK_ID_TOPLEVEL_XID. Author: Tomas Vondra, Dilip Kumar, Amit Kapila Reviewed-by: Amit Kapila Tested-by: Neha Sharma and Mahendra Singh Thalor Discussion: https://postgr.es/m/688b0b7f-2f6c-d827-c27b-216a8e3ea700@2ndquadrant.com	5 years ago
Alvaro Herrera	a8aaa0c786	Morph pg_replication_slots.min_safe_lsn to safe_wal_size ... The previous definition of the column was almost universally disliked, so provide this updated definition which is more useful for monitoring purposes: a large positive value is good, while zero or a negative value means danger. This should be operationally more convenient. Backpatch to 13, where the new column to pg_replication_slots (and the feature it represents) were added. Author: Kyotaro Horiguchi <horikyota.ntt@gmail.com> Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Reported-by: Fujii Masao <masao.fujii@oss.nttdata.com> Discussion: https://postgr.es/m/9ddfbf8c-2f67-904d-44ed-cf8bc5916228@oss.nttdata.com	6 years ago
Noah Misch	c6b92041d3	Skip WAL for new relfilenodes, under wal_level=minimal. ... Until now, only selected bulk operations (e.g. COPY) did this. If a given relfilenode received both a WAL-skipping COPY and a WAL-logged operation (e.g. INSERT), recovery could lose tuples from the COPY. See src/backend/access/transam/README section "Skipping WAL for New RelFileNode" for the new coding rules. Maintainers of table access methods should examine that section. To maintain data durability, just before commit, we choose between an fsync of the relfilenode and copying its contents to WAL. A new GUC, wal_skip_threshold, guides that choice. If this change slows a workload that creates small, permanent relfilenodes under wal_level=minimal, try adjusting wal_skip_threshold. Users setting a timeout on COMMIT may need to adjust that timeout, and log_min_duration_statement analysis will reflect time consumption moving to COMMIT from commands like COPY. Internally, this requires a reliable determination of whether RollbackAndReleaseCurrentSubTransaction() would unlink a relation's current relfilenode. Introduce rd_firstRelfilenodeSubid. Amend the specification of rd_createSubid such that the field is zero when a new rel has an old rd_node. Make relcache.c retain entries for certain dropped relations until end of transaction. Bump XLOG_PAGE_MAGIC, since this introduces XLOG_GIST_ASSIGN_LSN. Future servers accept older WAL, so this bump is discretionary. Kyotaro Horiguchi, reviewed (in earlier, similar versions) by Robert Haas. Heikki Linnakangas and Michael Paquier implemented earlier designs that materially clarified the problem. Reviewed, in earlier designs, by Andrew Dunstan, Andres Freund, Alvaro Herrera, Tom Lane, Fujii Masao, and Simon Riggs. Reported by Martijn van Oosterhout. Discussion: https://postgr.es/m/20150702220524.GA9392@svana.org	6 years ago
Michael Paquier	616ae3d2b0	Move routine definitions of xlogarchive.c to a new header file ... The definitions of the routines defined in xlogarchive.c have been part of xlog_internal.h which is included by several frontend tools, but all those routines are only called by the backend. More cleanup could be done within xlog_internal.h, but that's already a nice cut. This will help a follow-up patch for pg_rewind where handling of restore_command is added for frontends. Author: Alexey Kondratov, Michael Paquier Reviewed-by: Álvaro Herrera, Alexander Korotkov Discussion: https://postgr.es/m/a3acff50-5a0d-9a2c-b3b2-ee36168955c1@postgrespro.ru	6 years ago
Peter Geoghegan	0d861bbb70	Add deduplication to nbtree. ... Deduplication reduces the storage overhead of duplicates in indexes that use the standard nbtree index access method. The deduplication process is applied lazily, after the point where opportunistic deletion of LP_DEAD-marked index tuples occurs. Deduplication is only applied at the point where a leaf page split would otherwise be required. New posting list tuples are formed by merging together existing duplicate tuples. The physical representation of the items on an nbtree leaf page is made more space efficient by deduplication, but the logical contents of the page are not changed. Even unique indexes make use of deduplication as a way of controlling bloat from duplicates whose TIDs point to different versions of the same logical table row. The lazy approach taken by nbtree has significant advantages over a GIN style eager approach. Most individual inserts of index tuples have exactly the same overhead as before. The extra overhead of deduplication is amortized across insertions, just like the overhead of page splits. The key space of indexes works in the same way as it has since commit dd299df8 (the commit that made heap TID a tiebreaker column). Testing has shown that nbtree deduplication can generally make indexes with about 10 or 15 tuples for each distinct key value about 2.5X - 4X smaller, even with single column integer indexes (e.g., an index on a referencing column that accompanies a foreign key). The final size of single column nbtree indexes comes close to the final size of a similar contrib/btree_gin index, at least in cases where GIN's posting list compression isn't very effective. This can significantly improve transaction throughput, and significantly reduce the cost of vacuuming indexes. A new index storage parameter (deduplicate_items) controls the use of deduplication. The default setting is 'on', so all new B-Tree indexes automatically use deduplication where possible. This decision will be reviewed at the end of the Postgres 13 beta period. There is a regression of approximately 2% of transaction throughput with synthetic workloads that consist of append-only inserts into a table with several non-unique indexes, where all indexes have few or no repeated values. The underlying issue is that cycles are wasted on unsuccessful attempts at deduplicating items in non-unique indexes. There doesn't seem to be a way around it short of disabling deduplication entirely. Note that deduplication of items in unique indexes is fairly well targeted in general, which avoids the problem there (we can use a special heuristic to trigger deduplication passes in unique indexes, since we're specifically targeting "version bloat"). Bump XLOG_PAGE_MAGIC because xl_btree_vacuum changed. No bump in BTREE_VERSION, since the representation of posting list tuples works in a way that's backwards compatible with version 4 indexes (i.e. indexes built on PostgreSQL 12). However, users must still REINDEX a pg_upgrade'd index to use deduplication, regardless of the Postgres version they've upgraded from. This is the only way to set the new nbtree metapage flag indicating that deduplication is generally safe. Author: Anastasia Lubennikova, Peter Geoghegan Reviewed-By: Peter Geoghegan, Heikki Linnakangas Discussion: https://postgr.es/m/55E4051B.7020209@postgrespro.ru https://postgr.es/m/4ab6e2db-bcee-f4cf-0916-3a06e6ccbb55@postgrespro.ru	6 years ago
Peter Geoghegan	d2e5e20e57	Add xl_btree_delete optimization. ... Commit 558a9165e0 taught _bt_delitems_delete() to produce its own XID horizon on the primary. Standbys no longer needed to generate their own latestRemovedXid, since they could just use the explicitly logged value from the primary instead. The deleted offset numbers array from the xl_btree_delete WAL record was no longer used by the REDO routine for anything other than deleting the items. This enables a minor optimization: We now treat the array as buffer state, not generic WAL data, following _bt_delitems_vacuum()'s example. This should be a minor win, since it allows us to avoid including the deleted items array in cases where XLogInsert() stores the whole buffer anyway. The primary goal here is to make the code more maintainable, though. Removing inessential differences between the two functions highlights the fundamental differences that remain. Also change xl_btree_delete to use uint32 for the size of the array of item offsets being deleted. This brings xl_btree_delete closer to xl_btree_vacuum. Furthermore, it seems like a good idea to use an explicit-width integer type (the field was previously an "int"). Bump XLOG_PAGE_MAGIC because xl_btree_delete changed. Discussion: https://postgr.es/m/CAH2-Wzkz4TjmezzfAbaV1zYrh=fr0bCpzuJTvBe5iUQ3aUPsCQ@mail.gmail.com	6 years ago
Bruce Momjian	7559d8ebfa	Update copyrights for 2020 ... Backpatch-through: update all files in master, backpatch legal files through 9.4	6 years ago
Peter Geoghegan	9f83468b35	Remove unneeded "pin scan" nbtree VACUUM code. ... The REDO routine for nbtree's xl_btree_vacuum record type hasn't performed a "pin scan" since commit 3e4b7d87 went in, so clearly there isn't any point in VACUUM WAL-logging information that won't actually be used. Finish off the work of commit 3e4b7d87 (and the closely related preceding commit 687f2cd7) by removing the code that generates this unused information. Also remove the REDO routine code disabled by commit 3e4b7d87. Replace the unneeded lastBlockVacuumed field in xl_btree_vacuum with a new "ndeleted" field. The new field isn't actually needed right now, since we could continue to infer the array length from the overall record length. However, an upcoming patch to add deduplication to nbtree needs to add an "items updated" field to xl_btree_vacuum, so we might as well start being explicit about the number of items now. (Besides, it doesn't seem like a good idea to leave the xl_btree_vacuum struct without any fields; the C standard says that that's undefined.) nbtree VACUUM no longer forces writing a WAL record for the last block in the index. Writing out a WAL record with no items for the final block was supposed to force processing of a lastBlockVacuumed field by a pin scan. Bump XLOG_PAGE_MAGIC because xl_btree_vacuum changed. Discussion: https://postgr.es/m/CAH2-WzmY_mT7UnTzFB5LBQDBkKpdV5UxP3B5bLb7uP%3D%3D6UQJRQ%40mail.gmail.com	6 years ago
Michael Paquier	9989d37d1c	Remove XLogFileNameP() from the tree ... XLogFileNameP() is a wrapper routine able to build a palloc'd string for a WAL segment name, which is used for error string generation. There were several code paths where it gets called in a critical section, where memory allocation is not allowed. This results in triggering an assertion failure instead of generating the wanted error message. Another, more annoying, problem is that if the allocation to generate the WAL segment name fails on OOM, then the failure would be escalated to a PANIC. This removes the routine and all its callers are replaced with a logic using a fixed-size buffer. This way, all the existing mistakes are fixed and future ones are prevented. Author: Masahiko Sawada Reviewed-by: Michael Paquier, Álvaro Herrera Discussion: https://postgr.es/m/CA+fd4k5gC9H4uoWMLg9K_QfNrnkkdEw+-AFveob9YX7z8JnKTA@mail.gmail.com	6 years ago
Fujii Masao	43a54a3bcc	Bump WAL version. ... Oversight in commit e6d8069522. Since that commit changed the format of XLOG_DBASE_DROP WAL record, XLOG_PAGE_MAGIC needs to be bumped. Spotted by Michael Paquier	6 years ago
Michael Paquier	c96581abe4	Fix inconsistencies and typos in the tree, take 11 ... This fixes various typos in docs and comments, and removes some orphaned definitions. Author: Alexander Lakhin Discussion: https://postgr.es/m/5da8e325-c665-da95-21e0-c8a99ea61fbf@gmail.com	6 years ago
Michael Paquier	0896ae561b	Fix inconsistencies and typos in the tree ... This is numbered take 7, and addresses a set of issues around: - Fixes for typos and incorrect reference names. - Removal of unneeded comments. - Removal of unreferenced functions and structures. - Fixes regarding variable name consistency. Author: Alexander Lakhin Discussion: https://postgr.es/m/10bfd4ac-3e7c-40ab-2b2e-355ed15495e8@gmail.com	7 years ago
Tom Lane	8255c7a5ee	Phase 2 pgindent run for v12. ... Switch to 2.1 version of pg_bsd_indent. This formats multiline function declarations "correctly", that is with additional lines of parameter declarations indented to match where the first line's left parenthesis is. Discussion: https://postgr.es/m/CAEepm=0P3FeTXRcU5B2W3jv3PgRVZ-kGUXLGfd42FFhUROO3ug@mail.gmail.com	7 years ago
Tom Lane	be76af171c	Initial pgindent run for v12. ... This is still using the 2.0 version of pg_bsd_indent. I thought it would be good to commit this separately, so as to document the differences between 2.0 and 2.1 behavior. Discussion: https://postgr.es/m/16296.1558103386@sss.pgh.pa.us	7 years ago
Andres Freund	b5f58cf213	Convert gist to compute page level xid horizon on primary. ... Due to parallel development, gist added the missing conflict information in c952eae52a, while 558a9165e0 moved that computation to the primary for the index types that already had it. Thus adapt gist to also compute on the primary, using index_compute_xid_horizon_for_tuples() instead of its own copy of the logic. This also adds pg_waldump support for XLOG_GIST_DELETE records, which previously was not properly present. Bumps WAL version. Author: Andres Freund Discussion: https://postgr.es/m/20190406050243.bszosdg4buvabfrt@alap3.anarazel.de	7 years ago
Andres Freund	558a9165e0	Compute XID horizon for page level index vacuum on primary. ... Previously the xid horizon was only computed during WAL replay. That had two major problems: 1) It relied on knowing what the table pointed to looks like. That was easy enough before the introducing of tableam (we knew it had to be heap, although some trickery around logging the heap relfilenodes was required). But to properly handle table AMs we need per-database catalog access to look up the AM handler, which recovery doesn't allow. 2) Not knowing the xid horizon also makes it hard to support logical decoding on standbys. When on a catalog table, we need to be able to conflict with slots that have an xid horizon that's too old. But computing the horizon by visiting the heap only works once consistency is reached, but we always need to be able to detect conflicts. There's also a secondary problem, in that the current method performs redundant work on every standby. But that's counterbalanced by potentially computing the value when not necessary (either because there's no standby, or because there's no connected backends). Solve 1) and 2) by moving computation of the xid horizon to the primary and by involving tableam in the computation of the horizon. To address the potentially increased overhead, increase the efficiency of the xid horizon computation for heap by sorting the tids, and eliminating redundant buffer accesses. When prefetching is available, additionally perform prefetching of buffers. As this is more of a maintenance task, rather than something routinely done in every read only query, we add an arbitrary 10 to the effective concurrency - thereby using IO concurrency, when not globally enabled. That's possibly not the perfect formula, but seems good enough for now. Bumps WAL format, as latestRemovedXid is now part of the records, and the heap's relfilenode isn't anymore. Author: Andres Freund, Amit Khandekar, Robert Haas Reviewed-By: Robert Haas Discussion: https://postgr.es/m/20181212204154.nsxf3gzqv3gesl32@alap3.anarazel.de https://postgr.es/m/20181214014235.dal5ogljs3bmlq44@alap3.anarazel.de https://postgr.es/m/20180703070645.wchpu5muyto5n647@alap3.anarazel.de	7 years ago
Michael Paquier	ea92368cd1	Move max_wal_senders out of max_connections for connection slot handling ... Since its introduction, max_wal_senders is counted as part of max_connections when it comes to define how many connection slots can be used for replication connections with a WAL sender context. This can lead to confusion for some users, as it could be possible to block a base backup or replication from happening because other backend sessions are already taken for other purposes by an application, and superuser-only connection slots are not a correct solution to handle that case. This commit makes max_wal_senders independent of max_connections for its handling of PGPROC entries in ProcGlobal, meaning that connection slots for WAL senders are handled using their own free queue, like autovacuum workers and bgworkers. One compatibility issue that this change creates is that a standby now requires to have a value of max_wal_senders at least equal to its primary. So, if a standby created enforces the value of max_wal_senders to be lower than that, then this could break failovers. Normally this should not be an issue though, as any settings of a standby are inherited from its primary as postgresql.conf gets normally copied as part of a base backup, so parameters would be consistent. Author: Alexander Kukushkin Reviewed-by: Kyotaro Horiguchi, Petr Jelínek, Masahiko Sawada, Oleksii Kliukin Discussion: https://postgr.es/m/CAFh8B=nBzHQeYAu0b8fjK-AF1X4+_p6GRtwG+cCgs6Vci2uRuQ@mail.gmail.com	7 years ago
Bruce Momjian	97c39498e5	Update copyright for 2019 ... Backpatch-through: certain files through 9.4	7 years ago