19 Commits (60f1f09ff44308667ef6c72fbafd68235e55ae27)

Author	SHA1	Message	Date
Amit Kapila	19890a064e	Add option to enable two_phase commits via pg_create_logical_replication_slot. ... Commit 0aa8a01d04 extends the output plugin API to allow decoding of prepared xacts and allowed the user to enable/disable the two-phase option via pg_logical_slot_get_changes(). This can lead to a problem such that the first time when it gets changes via pg_logical_slot_get_changes() without two_phase option enabled it will not get the prepared even though prepare is after consistent snapshot. Now next time during getting changes, if the two_phase option is enabled it can skip prepare because by that time start decoding point has been moved. So the user will only get commit prepared. Allow to enable/disable this option at the create slot time and default will be false. It will break the existing slots which is fine in a major release. Author: Ajin Cherian Reviewed-by: Amit Kapila and Vignesh C Discussion: https://postgr.es/m/d0f60d60-133d-bf8d-bd70-47784d8fabf3@enterprisedb.com	5 years ago
Amit Kapila	e33d004900	Fix the test for decoding of two-phase transactions. ... Commit 5a3574d7b3 added the test for decoding of two-phase transactions during the build of a consistent snapshot. The test forgot to skip empty xacts which can lead to decoding of extra empty transactions due to background activity by autovacuum. Per report by buildfarm. Reported-by: Tom Lane Discussion: https://postgr.es/m/363512.1610171267@sss.pgh.pa.us	5 years ago
Amit Kapila	5a3574d7b3	Test decoding of two-phase transactions during the build of a consistent snapshot. ... Commit a271a1b50e added the capability to allow decoding at prepare time. This adds an isolation testcase to test that decoding happens at commit time when the consistent snapshot state is reached after prepare but before commit prepared. Author: Ajin Cherian Reviewed-by: Amit Kapila Discussion: https://postgr.es/m/02DA5F5E-CECE-4D9C-8B4B-418077E2C010@postgrespro.ru https://postgr.es/m/CAMGcDxeqEpWj3fTXwqhSwBdXd2RS9jzwWscO-XbeCfso6ts3+Q@mail.gmail.com	5 years ago
Amit Kapila	9653f24ad8	Fix 'skip-empty-xacts' option in test_decoding for streaming mode. ... In streaming mode, the transaction can be decoded in multiple streams and those streams can be interleaved with streams of other transactions. So, we can't remember the transaction's write status in the logical decoding context because that might get changed due to some other transactions and lead to wrong answers for 'skip-empty-xacts' option. We decided to keep each transaction's write status in the ReorderBufferTxn to avoid interleaved streams changing the status of some unrelated transactions. Diagnosed-by: Amit Kapila Author: Dilip Kumar Reviewed-by: Amit Kapila Discussion: https://postgr.es/m/CAA4eK1LR7=XNM_TLmpZMFuV8ZQpoxkem--NZJYf8YXmesbvwLA@mail.gmail.com	5 years ago
Amit Kapila	0ba5181c00	Skip empty transaction stream in test_decoding. ... We were decoding empty transactions via streaming APIs added in commit 45fdc9738b even when the user used the option 'skip-empty-xacts'. The APIs makes no effort to skip empty xacts under the assumption that we will never try to stream such transactions. However, that is not true because we can pick to stream a transaction that has change messages for REORDER_BUFFER_CHANGE_INTERNAL_SNAPSHOT and we don't send such messages to downstream rather they are just to update the internal state. So, we need to skip such xacts when plugin uses the option 'skip-empty-xacts'. Diagnosed-By: Amit Kapila Author: Dilip Kumar Reviewed-by: Amit Kapila Discussion: https://postgr.es/m/CAA4eK1+OqgFNZkf7=ETe_y5ntjgDk3T0wcdkd4Sot_u1hySGfw@mail.gmail.com	5 years ago
Thomas Munro	4c04be9b05	Introduce xid8-based functions to replace txid_XXX. ... The txid_XXX family of fmgr functions exposes 64 bit transaction IDs to users as int8. Now that we have an SQL type xid8 for FullTransactionId, define a new set of functions including pg_current_xact_id() and pg_current_snapshot() based on that. Keep the old functions around too, for now. It's a bit sneaky to use the same C functions for both, but since the binary representation is identical except for the signedness of the type, and since older functions are the ones using the wrong signedness, and since we'll presumably drop the older ones after a reasonable period of time, it seems reasonable to switch to FullTransactionId internally and share the code for both. Reviewed-by: Fujii Masao <masao.fujii@oss.nttdata.com> Reviewed-by: Takao Fujii <btfujiitkp@oss.nttdata.com> Reviewed-by: Yoshikazu Imai <imai.yoshikazu@fujitsu.com> Reviewed-by: Mark Dilger <mark.dilger@enterprisedb.com> Discussion: https://postgr.es/m/20190725000636.666m5mad25wfbrri%40alap3.anarazel.de	6 years ago
Amit Kapila	e3ff789acf	Stop demanding that top xact must be seen before subxact in decoding. ... Manifested as ERROR: subtransaction logged without previous top-level txn record this check forbids legit behaviours like - First xl_xact_assignment record is beyond reading, i.e. earlier restart_lsn. - After restart_lsn there is some change of a subxact. - After that, there is second xl_xact_assignment (for another subxact) revealing the relationship between top and first subxact. Such a transaction won't be streamed anyway because we hadn't seen it in full. Saying for sure whether xact of some record encountered after the snapshot was deserialized can be streamed or not requires to know whether it wrote something before deserialization point --if yes, it hasn't been seen in full and can't be decoded. Snapshot doesn't have such info, so there is no easy way to relax the check. Reported-by: Hsu, John Diagnosed-by: Arseny Sher Author: Arseny Sher, Amit Kapila Reviewed-by: Amit Kapila, Dilip Kumar Backpatch-through: 9.5 Discussion: https://postgr.es/m/AB5978B2-1772-4FEE-A245-74C91704ECB0@amazon.com	6 years ago
Michael Paquier	06fdc4e4d3	Do more cleanup of isolation tests for test_decoding ... 989d23b has caused its tests to be broken as the module defines unused steps, turning the buildfarm red.	6 years ago
Andres Freund	ef493055b6	Force synchronous commit to be enabled for all test_decoding tests. ... Without that the tests fail when forced to be run against a cluster with synchronous_commit = off (as the WAL might not yet be flushed to disk by the point logical decoding gets called, and thus the expected output breaks). Most tests already do that, add it to a few newer tests. Author: Andres Freund	7 years ago
Alvaro Herrera	8d1c1ca70b	Reduce cost of test_decoding's new oldest_xmin test ... Change a whole-database VACUUM into doing just pg_attribute, which is the portion that verifies what we want it to do. The original formulation wastes a lot of CPU time, which leads the test to fail when runtime exceeds isolationtester timeout when it's super-slow, such as under CLOBBER_CACHE_ALWAYS. Per buildfarm member friarbird. It turns out that the previous shape of the test doesn't always detect the condition it is supposed to detect (on unpatched reorderbuffer code): the reason is that there is a good chance of encountering a xl_running_xacts record (logged every 15 seconds) before the checkpoint -- and because we advance the xmin when we receive that WAL record, and we *don't* advance the xmin twice consecutively without receiving a client message in between, that means the xmin is not advanced enough for the tuple to be pruned from pg_attribute by VACUUM. So the test would spuriously pass. The reason this test deficiency wasn't detected earlier is that HOT pruning removes the tuple anyway, even if vacuum leaves it in place, so the test correctly fails (detecting the coding mistake), but for the wrong reason. To fix this mess, run the s0_get_changes step twice before vacuum instead of once: this seems to cause the xmin to be advanced reliably, wreaking havoc with more certainty. Author: Arseny Sher Discussion: https://postgr.es/m/87h8lkuxoa.fsf@ars-thinkpad	7 years ago
Alvaro Herrera	f49a80c481	Fix "base" snapshot handling in logical decoding ... Two closely related bugs are fixed. First, xmin of logical slots was advanced too early. During xl_running_xacts processing, xmin of the slot was set to the oldest running xid in the record, but that's wrong: actually, snapshots which will be used for not-yet-replayed transactions might consider older txns as running too, so we need to keep xmin back for them. The problem wasn't noticed earlier because DDL which allows to delete tuple (set xmax) while some another not-yet-committed transaction looks at it is pretty rare, if not unique: e.g. all forms of ALTER TABLE which change schema acquire ACCESS EXCLUSIVE lock conflicting with any inserts. The included test case (test_decoding's oldest_xmin) uses ALTER of a composite type, which doesn't have such interlocking. To deal with this, we must be able to quickly retrieve oldest xmin (oldest running xid among all assigned snapshots) from ReorderBuffer. To fix, add another list of ReorderBufferTXNs to the reorderbuffer, where transactions are sorted by base-snapshot-LSN. This is slightly different from the existing (sorted by first-LSN) list, because a transaction can have an earlier LSN but a later Xmin, if its first record does not obtain an xmin (eg. xl_xact_assignment). Note this new list doesn't fully replace the existing txn list: we still need that one to prevent WAL recycling. The second issue concerns SnapBuilder snapshots and subtransactions. SnapBuildDistributeNewCatalogSnapshot never assigned a snapshot to a transaction that is known to be a subtxn, which is good in the common case that the top-level transaction already has one (no point in doing so), but a bug otherwise. To fix, arrange to transfer the snapshot from the subtxn to its top-level txn as soon as the kinship gets known. test_decoding's snapshot_transfer verifies this. Also, fix a minor memory leak: refcount of toplevel's old base snapshot was not decremented when the snapshot is transferred from child. Liberally sprinkle code comments, and rewrite a few existing ones. This part is my (Álvaro's) contribution to this commit, as I had to write all those comments in order to understand the existing code and Arseny's patch. Reported-by: Arseny Sher <a.sher@postgrespro.ru> Diagnosed-by: Arseny Sher <a.sher@postgrespro.ru> Co-authored-by: Arseny Sher <a.sher@postgrespro.ru> Co-authored-by: Álvaro Herrera <alvherre@alvh.no-ip.org> Reviewed-by: Antonin Houska <ah@cybertec.at> Discussion: https://postgr.es/m/87lgdyz1wj.fsf@ars-thinkpad	7 years ago
Peter Eisentraut	325f2ec555	Handle heap rewrites even better in logical decoding ... Logical decoding should not publish anything about tables created as part of a heap rewrite during DDL. Those tables don't exist externally, so consumers of logical decoding cannot do anything sensible with that information. In ab28feae2b, we worked around this for built-in logical replication, but that was hack. This is a more proper fix: We mark such transient heaps using the new field pg_class.relwrite, linking to the original relation OID. By default, we ignore them in logical decoding before they get to the output plugin. Optionally, a plugin can register their interest in getting such changes, if they handle DDL specially, in which case the new field will help them get information about the actual table. Reviewed-by: Craig Ringer <craig@2ndquadrant.com>	8 years ago
Andres Freund	955a684e04	Fix race condition leading to hanging logical slot creation. ... The snapshot assembly during the creation of logical slots relied waiting for transactions in xl_running_xacts to end, by checking for their commit/abort records. Unfortunately, despite locking, it is possible to see an xl_running_xact record listing transactions as ready, that have already WAL-logged an commit/abort record, as the locking just prevents the ProcArray to be adjusted, and the commit record has to be logged first. That lead to either delayed or hanging snapshot creation, because snapbuild.c would wait "forever" to see commit/abort records for some transactions. That hang resolved only if a xl_running_xacts record without any running transactions happened to be logged, far from certain on a busy server. It's impractical to prevent that via more heavyweight locking, the likelihood of deadlocks and significantly increased contention would be too big. Instead change the initial snapshot creation to be solely based on tracking the oldest running transaction via xl_running_xacts->oldestRunningXid - that actually ends up significantly simplifying the code. That has two disadvantages: 1) Because we cannot fully "trust" the contents of xl_running_xacts, we cannot use it to build the initial snapshot. Instead we have to wait twice for all running transactions to finish. 2) Previously a slot, unless the race occurred, could be created when the all transaction perceived as running based on commit/abort records, now we have to wait for the next xl_running_xacts record. To address that, trigger logging new xl_running_xacts record from within snapbuild.c exactly when necessary. Unfortunately snabuild.c's SnapBuild is stored on disk, one of the stupider ideas of a certain Mr Freund, so we can't change it in a minor release. As this is going to be backpatched, we have to hack around a bit to keep on-disk compatibility. A later commit will rejigger that on master. Author: Andres Freund, based on a quite different patch from Petr Jelinek Analyzed-By: Petr Jelinek Reviewed-By: Petr Jelinek Discussion: https://postgr.es/m/f37e975c-908f-858e-707f-058d3b1eb214@2ndquadrant.com Backpatch: 9.4-, where logical decoding has been introduced	8 years ago
Andres Freund	1986c3c440	Force synchronous_commit=on in test_decoding's concurrent_ddl_dml.spec. ... Otherwise running installcheck-force on a server with synchronous_commit=off will result in the tests failing. All the other tests already do so... Backpatch: 9.4, where logical decoding was added	10 years ago
Robert Haas	5243a35825	Remove bogus step from test_decoding isolation tests. ... Commit 43b4a16817 made the isolation tester reject duplicate step names, and it turns out that the test_decoding module's concurrent_ddl_dml isolation test has a duplicate name. I think the second definition isn't actually getting used, so just remove it. Per buildfarm.	10 years ago
Heikki Linnakangas	4fc72cc7bb	Collection of typo fixes. ... Use "a" and "an" correctly, mostly in comments. Two error messages were also fixed (they were just elogs, so no translation work required). Two function comments in pg_proc.h were also fixed. Etsuro Fujita reported one of these, but I found a lot more with grep. Also fix a few other typos spotted while grepping for the a/an typos. For example, "consists out of ..." -> "consists of ...". Plus a "though"/ "through" mixup reported by Euler Taveira. Many of these typos were in old code, which would be nice to backpatch to make future backpatching easier. But much of the code was new, and I didn't feel like crafting separate patches for each branch. So no backpatching.	10 years ago
Andres Freund	ec5896aed3	Fix several weaknesses in slot and logical replication on-disk serialization. ... Heikki noticed in 544E23C0.8090605@vmware.com that slot.c and snapbuild.c were missing the FIN_CRC32 call when computing/checking checksums of on disk files. That doesn't lower the the error detection capabilities of the checksum, but is inconsistent with other usages. In a followup mail Heikki also noticed that, contrary to a comment, the 'version' and 'length' struct fields of replication slot's on disk data where not covered by the checksum. That's not likely to lead to actually missed corruption as those fields are cross checked with the expected version and the actual file length. But it's wrong nonetheless. As fixing these issues makes existing on disk files unreadable, bump the expected versions of on disk files for both slots and logical decoding historic catalog snapshots. This means that loading old files will fail with ERROR: "replication slot file ... has unsupported version 1" and ERROR: "snapbuild state file ... has unsupported version 1 instead of 2" respectively. Given the low likelihood of anybody already using these new features in a production setup that seems acceptable. Fixing these issues made me notice that there's no regression test covering the loading of historic snapshot from disk - so add one. Backpatch to 9.4 where these features were introduced.	11 years ago
Andres Freund	d6fa44fce7	Add skip-empty-xacts option to test_decoding for use in the regression tests. ... The regression tests for contrib/test_decoding regularly failed on postgres instances that were very slow. Either because the hardware itself was slow or because very expensive debugging options like CLOBBER_CACHE_ALWAYS were used. The reason they failed was just that some additional transactions were decoded. Analyze and vacuum, triggered by autovac. To fix just add a option to test_decoding to only display transactions in which a change was actually displayed. That's not pretty because it removes information from the tests; but better than constantly failing tests in very likely harmless ways. Backpatch to 9.4 where logical decoding was introduced. Discussion: 20140629142511.GA26930@awork2.anarazel.de	11 years ago
Robert Haas	b89e151054	Introduce logical decoding. ... This feature, building on previous commits, allows the write-ahead log stream to be decoded into a series of logical changes; that is, inserts, updates, and deletes and the transactions which contain them. It is capable of handling decoding even across changes to the schema of the effected tables. The output format is controlled by a so-called "output plugin"; an example is included. To make use of this in a real replication system, the output plugin will need to be modified to produce output in the format appropriate to that system, and to perform filtering. Currently, information can be extracted from the logical decoding system only via SQL; future commits will add the ability to stream changes via walsender. Andres Freund, with review and other contributions from many other people, including Álvaro Herrera, Abhijit Menon-Sen, Peter Gheogegan, Kevin Grittner, Robert Haas, Heikki Linnakangas, Fujii Masao, Abhijit Menon-Sen, Michael Paquier, Simon Riggs, Craig Ringer, and Steve Singer.	12 years ago