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2021-09-04Revert "Avoid creating archive status ".ready" files too early"Alvaro Herrera
This reverts commit 515e3d84a0b5 and equivalent commits in back branches. This solution to the problem has a number of problems, so we'll try again with a different approach. Per note from Andres Freund Discussion: https://postgr.es/m/20210831042949.52eqp5xwbxgrfank@alap3.anarazel.de
2021-08-25Fix toast rewrites in logical decoding.Amit Kapila
Commit 325f2ec555 introduced pg_class.relwrite to skip operations on tables created as part of a heap rewrite during DDL. It links such transient heaps to the original relation OID via this new field in pg_class but forgot to do anything about toast tables. So, logical decoding was not able to skip operations on internally created toast tables. This leads to an error when we tried to decode the WAL for the next operation for which it appeared that there is a toast data where actually it didn't have any toast data. To fix this, we set pg_class.relwrite for internally created toast tables as well which allowed skipping operations on them during logical decoding. Author: Bertrand Drouvot Reviewed-by: David Zhang, Amit Kapila Backpatch-through: 11, where it was introduced Discussion: https://postgr.es/m/b5146fb1-ad9e-7d6e-f980-98ed68744a7c@amazon.com
2021-08-23Avoid creating archive status ".ready" files too earlyAlvaro Herrera
WAL records may span multiple segments, but XLogWrite() does not wait for the entire record to be written out to disk before creating archive status files. Instead, as soon as the last WAL page of the segment is written, the archive status file is created, and the archiver may process it. If PostgreSQL crashes before it is able to write and flush the rest of the record (in the next WAL segment), the wrong version of the first segment file lingers in the archive, which causes operations such as point-in-time restores to fail. To fix this, keep track of records that span across segments and ensure that segments are only marked ready-for-archival once such records have been completely written to disk. This has always been wrong, so backpatch all the way back. Author: Nathan Bossart <bossartn@amazon.com> Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com> Reviewed-by: Ryo Matsumura <matsumura.ryo@fujitsu.com> Reviewed-by: Andrey Borodin <x4mmm@yandex-team.ru> Discussion: https://postgr.es/m/CBDDFA01-6E40-46BB-9F98-9340F4379505@amazon.com
2021-08-19Avoid trying to lock OLD/NEW in a rule with FOR UPDATE.Tom Lane
transformLockingClause neglected to exclude the pseudo-RTEs for OLD/NEW when processing a rule's query. This led to odd errors or even crashes later on. This bug is very ancient, but it's not terribly surprising that nobody noticed, since the use-case for SELECT FOR UPDATE in a non-view rule is somewhere between thin and non-existent. Still, crashing is not OK. Per bug #17151 from Zhiyong Wu. Thanks to Masahiko Sawada for analysis of the problem. Discussion: https://postgr.es/m/17151-c03a3e6e4ec9aadb@postgresql.org
2021-08-17Prevent ALTER TYPE/DOMAIN/OPERATOR from changing extension membership.Tom Lane
If recordDependencyOnCurrentExtension is invoked on a pre-existing, free-standing object during an extension update script, that object will become owned by the extension. In our current code this is possible in three cases: * Replacing a "shell" type or operator. * CREATE OR REPLACE overwriting an existing object. * ALTER TYPE SET, ALTER DOMAIN SET, and ALTER OPERATOR SET. The first of these cases is intentional behavior, as noted by the existing comments for GenerateTypeDependencies. It seems like appropriate behavior for CREATE OR REPLACE too; at least, the obvious alternatives are not better. However, the fact that it happens during ALTER is an artifact of trying to share code (GenerateTypeDependencies and makeOperatorDependencies) between the CREATE and ALTER cases. Since an extension script would be unlikely to ALTER an object that didn't already belong to the extension, this behavior is not very troubling for the direct target object ... but ALTER TYPE SET will recurse to dependent domains, and it is very uncool for those to become owned by the extension if they were not already. Let's fix this by redefining the ALTER cases to never change extension membership, full stop. We could minimize the behavioral change by only changing the behavior when ALTER TYPE SET is recursing to a domain, but that would complicate the code and it does not seem like a better definition. Per bug #17144 from Alex Kozhemyakin. Back-patch to v13 where ALTER TYPE SET was added. (The other cases are older, but since they only affect the directly-named object, there's not enough of a problem to justify changing the behavior further back.) Discussion: https://postgr.es/m/17144-e67d7a8f049de9af@postgresql.org
2021-08-13Add RISC-V spinlock support in s_lock.h.Tom Lane
Like the ARM case, just use gcc's __sync_lock_test_and_set(); that will compile into AMOSWAP.W.AQ which does what we need. At some point it might be worth doing some work on atomic ops for RISC-V, but this should be enough for a creditable port. Back-patch to all supported branches, just in case somebody wants to try them on RISC-V. Marek Szuba Discussion: https://postgr.es/m/dea97b6d-f55f-1f6d-9109-504aa7dfa421@gentoo.org
2021-08-13Fix incorrect hash table resizing code in simplehash.hDavid Rowley
This fixes a bug in simplehash.h which caused an incorrect size mask to be used when the hash table grew to SH_MAX_SIZE (2^32). The code was incorrectly setting the size mask to 0 when the hash tables reached the maximum possible number of buckets. This would result always trying to use the 0th bucket causing an infinite loop of trying to grow the hash table due to there being too many collisions. Seemingly it's not that common for simplehash tables to ever grow this big as this bug dates back to v10 and nobody seems to have noticed it before. However, probably the most likely place that people would notice it would be doing a large in-memory Hash Aggregate with something close to at least 2^31 groups. After this fix, the code now works correctly with up to within 98% of 2^32 groups and will fail with the following error when trying to insert any more items into the hash table: ERROR: hash table size exceeded However, the work_mem (or hash_mem_multiplier in newer versions) settings will generally cause Hash Aggregates to spill to disk long before reaching that many groups. The minimal test case I did took a work_mem setting of over 192GB to hit the bug. simplehash hash tables are used in a few other places such as Bitmap Index Scans, however, again the size that the hash table can become there is also limited to work_mem and it would take a relation of around 16TB (2^31) pages and a very large work_mem setting to hit this. With smaller work_mem values the table would become lossy and never grow large enough to hit the problem. Author: Yura Sokolov Reviewed-by: David Rowley, Ranier Vilela Discussion: https://postgr.es/m/b1f7f32737c3438136f64b26f4852b96@postgrespro.ru Backpatch-through: 10, where simplehash.h was added
2021-07-25Get rid of artificial restriction on hash table sizes on Windows.Tom Lane
The point of introducing the hash_mem_multiplier GUC was to let users reproduce the old behavior of hash aggregation, i.e. that it could use more than work_mem at need. However, the implementation failed to get the job done on Win64, where work_mem is clamped to 2GB to protect various places that calculate memory sizes using "long int". As written, the same clamp was applied to hash_mem. This resulted in severe performance regressions for queries requiring a bit more than 2GB for hash aggregation, as they now spill to disk and there's no way to stop that. Getting rid of the work_mem restriction seems like a good idea, but it's a big job and could not conceivably be back-patched. However, there's only a fairly small number of places that are concerned with the hash_mem value, and it turns out to be possible to remove the restriction there without too much code churn or any ABI breaks. So, let's do that for now to fix the regression, and leave the larger task for another day. This patch does introduce a bit more infrastructure that should help with the larger task, namely pg_bitutils.h support for working with size_t values. Per gripe from Laurent Hasson. Back-patch to v13 where the behavior change came in. Discussion: https://postgr.es/m/997817.1627074924@sss.pgh.pa.us Discussion: https://postgr.es/m/MN2PR15MB25601E80A9B6D1BA6F592B1985E39@MN2PR15MB2560.namprd15.prod.outlook.com
2021-07-16Preserve firing-on state when cloning row triggers to partitionsAlvaro Herrera
When triggers are cloned from partitioned tables to their partitions, the 'tgenabled' flag (origin/replica/always/disable) was not propagated. Make it so that the flag on the trigger on partition is initially set to the same value as on the partitioned table. Add a test case to verify the behavior. Backpatch to 11, where this appeared in commit 86f575948c77. Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Reported-by: Justin Pryzby <pryzby@telsasoft.com> Discussion: https://postgr.es/m/20200930223450.GA14848@telsasoft.com
2021-07-16Advance old-segment horizon properly after slot invalidationAlvaro Herrera
When some slots are invalidated due to the max_slot_wal_keep_size limit, the old segment horizon should move forward to stay within the limit. However, in commit c6550776394e we forgot to call KeepLogSeg again to recompute the horizon after invalidating replication slots. In cases where other slots remained, the limits would be recomputed eventually for other reasons, but if all slots were invalidated, the limits would not move at all afterwards. Repair. Backpatch to 13 where the feature was introduced. Author: Kyotaro Horiguchi <horikyota.ntt@gmail.com> Reported-by: Marcin Krupowicz <mk@071.ovh> Discussion: https://postgr.es/m/17103-004130e8f27782c9@postgresql.org
2021-07-09Update configure's probe for libldap to work with OpenLDAP 2.5.Tom Lane
The separate libldap_r is gone and libldap itself is now always thread-safe. Unfortunately there seems no easy way to tell by inspection whether libldap is thread-safe, so we have to take it on faith that libldap is thread-safe if there's no libldap_r. That should be okay, as it appears that libldap_r was a standard part of the installation going back at least 20 years. Report and patch by Adrian Ho. Back-patch to all supported branches, since people might try to build any of them with a newer OpenLDAP. Discussion: https://postgr.es/m/17083-a19190d9591946a7@postgresql.org
2021-07-02Don't try to print data type names in slot_store_error_callback().Tom Lane
The existing code tried to do syscache lookups in an already-failed transaction, which is problematic to say the least. After some consideration of alternatives, the best fix seems to be to just drop type names from the error message altogether. The table and column names seem like sufficient localization. If the user is unsure what types are involved, she can check the local and remote table definitions. Having done that, we can also discard the LogicalRepTypMap hash table, which had no other use. Arguably, LOGICAL_REP_MSG_TYPE replication messages are now obsolete as well; but we should probably keep them in case some other use emerges. (The complexity of removing something from the replication protocol would likely outweigh any savings anyhow.) Masahiko Sawada and Bharath Rupireddy, per complaint from Andres Freund. Back-patch to v10 where this code originated. Discussion: https://postgr.es/m/20210106020229.ne5xnuu6wlondjpe@alap3.anarazel.de
2021-06-24Fix ABI break introduced by commit 4daa140a2f.Amit Kapila
Move the newly defined enum value REORDER_BUFFER_CHANGE_INTERNAL_SPEC_ABORT at the end to avoid ABI break in the back branches. We need to back-patch this till v11 because before that it is already at the end. Reported-by: Tomas Vondra Backpatch-through: 11 Discussion: https://postgr.es/m/CAExHW5sPKF-Oovx_qZe4p5oM6Dvof7_P+XgsNAViug15Fm99jA@mail.gmail.com
2021-06-15Fix decoding of speculative aborts.Amit Kapila
During decoding for speculative inserts, we were relying for cleaning toast hash on confirmation records or next change records. But that could lead to multiple problems (a) memory leak if there is neither a confirmation record nor any other record after toast insertion for a speculative insert in the transaction, (b) error and assertion failures if the next operation is not an insert/update on the same table. The fix is to start queuing spec abort change and clean up toast hash and change record during its processing. Currently, we are queuing the spec aborts for both toast and main table even though we perform cleanup while processing the main table's spec abort record. Later, if we have a way to distinguish between the spec abort record of toast and the main table, we can avoid queuing the change for spec aborts of toast tables. Reported-by: Ashutosh Bapat Author: Dilip Kumar Reviewed-by: Amit Kapila Backpatch-through: 9.6, where it was introduced Discussion: https://postgr.es/m/CAExHW5sPKF-Oovx_qZe4p5oM6Dvof7_P+XgsNAViug15Fm99jA@mail.gmail.com
2021-06-08Remove unnecessary declaration in win32_port.hMichael Paquier
Mis-merge introduced by e2f21ff, where pgwin32_setenv() was listed but not defined in win32env.c. This had no consequences as this routine does not exist in this branch. Only REL_12_STABLE and REL_13_STABLE got that wrong. Backpatch-through: 12
2021-06-07Fix incautious handling of possibly-miscoded strings in client code.Tom Lane
An incorrectly-encoded multibyte character near the end of a string could cause various processing loops to run past the string's terminating NUL, with results ranging from no detectable issue to a program crash, depending on what happens to be in the following memory. This isn't an issue in the server, because we take care to verify the encoding of strings before doing any interesting processing on them. However, that lack of care leaked into client-side code which shouldn't assume that anyone has validated the encoding of its input. Although this is certainly a bug worth fixing, the PG security team elected not to regard it as a security issue, primarily because any untrusted text should be sanitized by PQescapeLiteral or the like before being incorporated into a SQL or psql command. (If an app fails to do so, the same technique can be used to cause SQL injection, with probably much more dire consequences than a mere client-program crash.) Those functions were already made proof against this class of problem, cf CVE-2006-2313. To fix, invent PQmblenBounded() which is like PQmblen() except it won't return more than the number of bytes remaining in the string. In HEAD we can make this a new libpq function, as PQmblen() is. It seems imprudent to change libpq's API in stable branches though, so in the back branches define PQmblenBounded as a macro in the files that need it. (Note that just changing PQmblen's behavior would not be a good idea; notably, it would completely break the escaping functions' defense against this exact problem. So we just want a version for those callers that don't have any better way of handling this issue.) Per private report from houjingyi. Back-patch to all supported branches.
2021-06-01Add fallback implementation for setenv()Michael Paquier
This fixes the code compilation on Windows with MSVC and Kerberos, as a missing implementation of setenv() causes a compilation failure of the GSSAPI code. This was only reproducible when building the code with Kerberos, something that buildfarm animal hamerkop has fixed recently. This issue only happens on 12 and 13, as this code has been introduced in b0b39f7. HEAD is already able to compile properly thanks to 7ca37fb0, and this commit is a minimal cherry-pick of it. Thanks to Tom Lane for the discussion. Discussion: https://postgr.es/m/YLDtm5WGjPxm6ua4@paquier.xyz Backpatch-through: 12
2021-05-21Restore the portal-level snapshot after procedure COMMIT/ROLLBACK.Tom Lane
COMMIT/ROLLBACK necessarily destroys all snapshots within the session. The original implementation of intra-procedure transactions just cavalierly did that, ignoring the fact that this left us executing in a rather different environment than normal. In particular, it turns out that handling of toasted datums depends rather critically on there being an outer ActiveSnapshot: otherwise, when SPI or the core executor pop whatever snapshot they used and return, it's unsafe to dereference any toasted datums that may appear in the query result. It's possible to demonstrate "no known snapshots" and "missing chunk number N for toast value" errors as a result of this oversight. Historically this outer snapshot has been held by the Portal code, and that seems like a good plan to preserve. So add infrastructure to pquery.c to allow re-establishing the Portal-owned snapshot if it's not there anymore, and add enough bookkeeping support that we can tell whether it is or not. We can't, however, just re-establish the Portal snapshot as part of COMMIT/ROLLBACK. As in normal transaction start, acquiring the first snapshot should wait until after SET and LOCK commands. Hence, teach spi.c about doing this at the right time. (Note that this patch doesn't fix the problem for any PLs that try to run intra-procedure transactions without using SPI to execute SQL commands.) This makes SPI's no_snapshots parameter rather a misnomer, so in HEAD, rename that to allow_nonatomic. replication/logical/worker.c also needs some fixes, because it wasn't careful to hold a snapshot open around AFTER trigger execution. That code doesn't use a Portal, which I suspect someday we're gonna have to fix. But for now, just rearrange the order of operations. This includes back-patching the recent addition of finish_estate() to centralize the cleanup logic there. This also back-patches commit 2ecfeda3e into v13, to improve the test coverage for worker.c (it was that test that exposed that worker.c's snapshot management is wrong). Per bug #15990 from Andreas Wicht. Back-patch to v11 where intra-procedure COMMIT was added. Discussion: https://postgr.es/m/15990-eee2ac466b11293d@postgresql.org
2021-05-14Refactor CHECK_FOR_INTERRUPTS() to add flexibility.Tom Lane
Split up CHECK_FOR_INTERRUPTS() to provide an additional macro INTERRUPTS_PENDING_CONDITION(), which just tests whether an interrupt is pending without attempting to service it. This is useful in situations where the caller knows that interrupts are blocked, and would like to find out if it's worth the trouble to unblock them. Also add INTERRUPTS_CAN_BE_PROCESSED(), which indicates whether CHECK_FOR_INTERRUPTS() can be relied on to clear the pending interrupt. This commit doesn't actually add any uses of the new macros, but a follow-on bug fix will do so. Back-patch to all supported branches to provide infrastructure for that fix. Alvaro Herrera and Tom Lane Discussion: https://postgr.es/m/20210513155351.GA7848@alvherre.pgsql
2021-05-12Rename the logical replication global "wrconn"Alvaro Herrera
The worker.c global wrconn is only meant to be used by logical apply/ tablesync workers, but there are other variables with the same name. To reduce future confusion rename the global from "wrconn" to "LogRepWorkerWalRcvConn". While this is just cosmetic, it seems better to backpatch it all the way back to 10 where this code appeared, to avoid future backpatching issues. Author: Peter Smith <smithpb2250@gmail.com> Discussion: https://postgr.es/m/CAHut+Pu7Jv9L2BOEx_Z0UtJxfDevQSAUW2mJqWU+CtmDrEZVAg@mail.gmail.com
2021-05-10Fix mishandling of resjunk columns in ON CONFLICT ... UPDATE tlists.Tom Lane
It's unusual to have any resjunk columns in an ON CONFLICT ... UPDATE list, but it can happen when MULTIEXPR_SUBLINK SubPlans are present. If it happens, the ON CONFLICT UPDATE code path would end up storing tuples that include the values of the extra resjunk columns. That's fairly harmless in the short run, but if new columns are added to the table then the values would become accessible, possibly leading to malfunctions if they don't match the datatypes of the new columns. This had escaped notice through a confluence of missing sanity checks, including * There's no cross-check that a tuple presented to heap_insert or heap_update matches the table rowtype. While it's difficult to check that fully at reasonable cost, we can easily add assertions that there aren't too many columns. * The output-column-assignment cases in execExprInterp.c lacked any sanity checks on the output column numbers, which seems like an oversight considering there are plenty of assertion checks on input column numbers. Add assertions there too. * We failed to apply nodeModifyTable's ExecCheckPlanOutput() to the ON CONFLICT UPDATE tlist. That wouldn't have caught this specific error, since that function is chartered to ignore resjunk columns; but it sure seems like a bad omission now that we've seen this bug. In HEAD, the right way to fix this is to make the processing of ON CONFLICT UPDATE tlists work the same as regular UPDATE tlists now do, that is don't add "SET x = x" entries, and use ExecBuildUpdateProjection to evaluate the tlist and combine it with old values of the not-set columns. This adds a little complication to ExecBuildUpdateProjection, but allows removal of a comparable amount of now-dead code from the planner. In the back branches, the most expedient solution seems to be to (a) use an output slot for the ON CONFLICT UPDATE projection that actually matches the target table, and then (b) invent a variant of ExecBuildProjectionInfo that can be told to not store values resulting from resjunk columns, so it doesn't try to store into nonexistent columns of the output slot. (We can't simply ignore the resjunk columns altogether; they have to be evaluated for MULTIEXPR_SUBLINK to work.) This works back to v10. In 9.6, projections work much differently and we can't cheaply give them such an option. The 9.6 version of this patch works by inserting a JunkFilter when it's necessary to get rid of resjunk columns. In addition, v11 and up have the reverse problem when trying to perform ON CONFLICT UPDATE on a partitioned table. Through a further oversight, adjust_partition_tlist() discarded resjunk columns when re-ordering the ON CONFLICT UPDATE tlist to match a partition. This accidentally prevented the storing-bogus-tuples problem, but at the cost that MULTIEXPR_SUBLINK cases didn't work, typically crashing if more than one row has to be updated. Fix by preserving resjunk columns in that routine. (I failed to resist the temptation to add more assertions there too, and to do some minor code beautification.) Per report from Andres Freund. Back-patch to all supported branches. Security: CVE-2021-32028
2021-05-10Prevent integer overflows in array subscripting calculations.Tom Lane
While we were (mostly) careful about ensuring that the dimensions of arrays aren't large enough to cause integer overflow, the lower bound values were generally not checked. This allows situations where lower_bound + dimension overflows an integer. It seems that that's harmless so far as array reading is concerned, except that array elements with subscripts notionally exceeding INT_MAX are inaccessible. However, it confuses various array-assignment logic, resulting in a potential for memory stomps. Fix by adding checks that array lower bounds aren't large enough to cause lower_bound + dimension to overflow. (Note: this results in disallowing cases where the last subscript position would be exactly INT_MAX. In principle we could probably allow that, but there's a lot of code that computes lower_bound + dimension and would need adjustment. It seems doubtful that it's worth the trouble/risk to allow it.) Somewhat independently of that, array_set_element() was careless about possible overflow when checking the subscript of a fixed-length array, creating a different route to memory stomps. Fix that too. Security: CVE-2021-32027
2021-04-20Fix planner failure in some cases of sorting by an aggregate.Tom Lane
An oversight introduced by the incremental-sort patches caused "could not find pathkey item to sort" errors in some situations where a sort key involves an aggregate or window function. The basic problem here is that find_em_expr_usable_for_sorting_rel isn't properly modeling what prepare_sort_from_pathkeys will do later. Rather than hoping we can keep those functions in sync, let's refactor so that they actually share the code for identifying a suitable sort expression. With this refactoring, tlist.c's tlist_member_ignore_relabel is unused. I removed it in HEAD but left it in place in v13, in case any extensions are using it. Per report from Luc Vlaming. Back-patch to v13 where the problem arose. James Coleman and Tom Lane Discussion: https://postgr.es/m/91f3ec99-85a4-fa55-ea74-33f85a5c651f@swarm64.com
2021-04-13Redesign the caching done by get_cached_rowtype().Tom Lane
Previously, get_cached_rowtype() cached a pointer to a reference-counted tuple descriptor from the typcache, relying on the ExprContextCallback mechanism to release the tupdesc refcount when the expression tree using the tupdesc was destroyed. This worked fine when it was designed, but the introduction of within-DO-block COMMITs broke it. The refcount is logged in a transaction-lifespan resource owner, but plpgsql won't destroy simple expressions made within the DO block (before its first commit) until the DO block is exited. That results in a warning about a leaked tupdesc refcount when the COMMIT destroys the original resource owner, and then an error about the active resource owner not holding a matching refcount when the expression is destroyed. To fix, get rid of the need to have a shutdown callback at all, by instead caching a pointer to the relevant typcache entry. Those survive for the life of the backend, so we needn't worry about the pointer becoming stale. (For registered RECORD types, we can still cache a pointer to the tupdesc, knowing that it won't change for the life of the backend.) This mechanism has been in use in plpgsql and expandedrecord.c since commit 4b93f5799, and seems to work well. This change requires modifying the ExprEvalStep structs used by the relevant expression step types, which is slightly worrisome for back-patching. However, there seems no good reason for extensions to be familiar with the details of these particular sub-structs. Per report from Rohit Bhogate. Back-patch to v11 where within-DO-block COMMITs became a thing. Discussion: https://postgr.es/m/CAAV6ZkQRCVBh8qAY+SZiHnz+U+FqAGBBDaDTjF2yiKa2nJSLKg@mail.gmail.com
2021-03-23Use correct spelling of statistics kindTomas Vondra
A couple error messages and comments used 'statistic kind', not the correct 'statistics kind'. Fix and backpatch all the way back to 10, where extended statistics were introduced. Backpatch-through: 10
2021-03-22Fix concurrency issues with WAL segment recycling on WindowsMichael Paquier
This commit is mostly a revert of aaa3aed, that switched the routine doing the internal renaming of recycled WAL segments to use on Windows a combination of CreateHardLinkA() plus unlink() instead of rename(). As reported by several users of Postgres 13, this is causing concurrency issues when manipulating WAL segments, mostly in the shape of the following error: LOG: could not rename file "pg_wal/000000XX000000YY000000ZZ": Permission denied This moves back to a logic where a single rename() (well, pgrename() for Windows) is used. This issue has proved to be hard to hit when I tested it, facing it only once with an archive_command that was not able to do its work, so it is environment-sensitive. The reporters of this issue have been able to confirm that the situation improved once we switched back to a single rename(). In order to check things, I have provided to the reporters a patched build based on 13.2 with aaa3aed reverted, to test if the error goes away, and an unpatched build of 13.2 to test if the error still showed up (just to make sure that I did not mess up my build process). Extra thanks to Fujii Masao for pointing out what looked like the culprit commit, and to all the reporters for taking the time to test what I have sent them. Reported-by: Andrus, Guy Burgess, Yaroslav Pashinsky, Thomas Trenz Reviewed-by: Tom Lane, Andres Freund Discussion: https://postgr.es/m/3861ff1e-0923-7838-e826-094cc9bef737@hot.ee Discussion: https://postgr.es/m/16874-c3eecd319e36a2bf@postgresql.org Discussion: https://postgr.es/m/095ccf8d-7f58-d928-427c-b17ace23cae6@burgess.co.nz Discussion: https://postgr.es/m/16927-67c570d968c99567%40postgresql.org Discussion: https://postgr.es/m/YFBcRbnBiPdGZvfW@paquier.xyz Backpatch-through: 13
2021-03-18Don't leak compiled regex(es) when an ispell cache entry is dropped.Tom Lane
The text search cache mechanisms assume that we can clean up an invalidated dictionary cache entry simply by resetting the associated long-lived memory context. However, that does not work for ispell affixes that make use of regular expressions, because the regex library deals in plain old malloc. Hence, we leaked compiled regex(es) any time we dropped such a cache entry. That could quickly add up, since even a fairly trivial regex can use up tens of kB, and a large one can eat megabytes. Add a memory context callback to ensure that a regex gets freed when its owning cache entry is cleared. Found via valgrind testing. This problem is ancient, so back-patch to all supported branches. Discussion: https://postgr.es/m/3816764.1616104288@sss.pgh.pa.us
2021-03-18Revert "Fix race in Parallel Hash Join batch cleanup."Thomas Munro
This reverts commit 4e0f0995e923948631c4114ab353b256b51b58ad. Discussion: https://postgr.es/m/CA%2BhUKGJmcqAE3MZeDCLLXa62cWM0AJbKmp2JrJYaJ86bz36LFA%40mail.gmail.com
2021-03-17Fix race in Parallel Hash Join batch cleanup.Thomas Munro
With very unlucky timing and parallel_leader_participation off, PHJ could attempt to access per-batch state just as it was being freed. There was code intended to prevent that by checking for a cleared pointer, but it was buggy. Fix, by introducing an extra barrier phase. The new phase PHJ_BUILD_RUNNING means that it's safe to access the per-batch state to find a batch to help with, and PHJ_BUILD_DONE means that it is too late. The last to detach will free the array of per-batch state as before, but now it will also atomically advance the phase at the same time, so that late attachers can avoid the hazard, without the data race. This mirrors the way per-batch hash tables are freed (see phases PHJ_BATCH_PROBING and PHJ_BATCH_DONE). Revealed by a one-off build farm failure, where BarrierAttach() failed a sanity check assertion, because the memory had been clobbered by dsa_free(). Back-patch to 11, where the code arrived. Reported-by: Michael Paquier <michael@paquier.xyz> Discussion: https://postgr.es/m/20200929061142.GA29096%40paquier.xyz
2021-02-16Convert tsginidx.c's GIN indexing logic to fully ternary operation.Tom Lane
Commit 2f2007fbb did this partially, but there were two remaining warts. checkcondition_gin handled some uncertain cases by setting the out-of-band recheck flag, some by returning TS_MAYBE, and some by doing both. Meanwhile, TS_execute arbitrarily converted a TS_MAYBE result to TS_YES. Thus, if checkcondition_gin chose to only return TS_MAYBE, the outcome would be TS_YES with no recheck flag, potentially resulting in wrong query outputs. The case where this'd happen is if there were GIN_MAYBE entries in the indexscan results passed to gin_tsquery_[tri]consistent, which so far as I can see would only happen if the tidbitmap used to accumulate indexscan results grew large enough to become lossy. I initially thought of fixing this by ensuring we always set the recheck flag as well as returning TS_MAYBE in uncertain cases. But that errs in the other direction, potentially forcing rechecks of rows that provably match the query (since the recheck flag remains set even if TS_execute later finds that the answer must be TS_YES). Instead, let's get rid of the out-of-band recheck flag altogether and rely on returning TS_MAYBE. This requires exporting a version of TS_execute that will actually return the full ternary result of the evaluation ... but we likely should have done that to start with. Unfortunately it doesn't seem practical to add a regression test case that covers this: the amount of data needed to cause the GIN bitmap to become lossy results in a longer runtime than I think we want to have in the tests. (I'm wondering about allowing smaller work_mem settings to ameliorate that, but it'd be a matter for a separate patch.) Per bug #16865 from Dimitri Nüscheler. Back-patch to v13 where the faulty commit came in. Discussion: https://postgr.es/m/16865-4ffdc3e682e6d75b@postgresql.org
2021-02-15Make ExecGetInsertedCols() and friends more robust and improve comments.Heikki Linnakangas
If ExecGetInsertedCols(), ExecGetUpdatedCols() or ExecGetExtraUpdatedCols() were called with a ResultRelInfo that's not in the range table and isn't a partition routing target, the functions would dereference a NULL pointer, relinfo->ri_RootResultRelInfo. Such ResultRelInfos are created when firing RI triggers in tables that are not modified directly. None of the current callers of these functions pass such relations, so this isn't a live bug, but let's make them more robust. Also update comment in ResultRelInfo; after commit 6214e2b228, ri_RangeTableIndex is zero for ResultRelInfos created for partition tuple routing. Noted by Coverity. Backpatch down to v11, like commit 6214e2b228. Reviewed-by: Tom Lane, Amit Langote
2021-02-15Default to wal_sync_method=fdatasync on FreeBSD.Thomas Munro
FreeBSD 13 gained O_DSYNC, which would normally cause wal_sync_method to choose open_datasync as its default value. That may not be a good choice for all systems, and performs worse than fdatasync in some scenarios. Let's preserve the existing default behavior for now. Like commit 576477e73c4, which did the same for Linux, back-patch to all supported releases. Discussion: https://postgr.es/m/CA%2BhUKGLsAMXBQrCxCXoW-JsUYmdOL8ALYvaX%3DCrHqWxm-nWbGA%40mail.gmail.com
2021-02-13pg_attribute_no_sanitize_alignment() macroTom Lane
Modern gcc and clang compilers offer alignment sanitizers, which help to detect pointer misalignment. However, our codebase already contains x86-specific crc32 computation code, which uses unalignment access. Thankfully, those compilers also support the attribute, which disables alignment sanitizers at the function level. This commit adds pg_attribute_no_sanitize_alignment(), which wraps this attribute, and applies it to pg_comp_crc32c_sse42() function. Back-patch of commits 993bdb9f9 and ad2ad698a, to enable doing alignment testing in all supported branches. Discussion: https://postgr.es/m/CAPpHfdsne3%3DT%3DfMNU45PtxdhSL_J2PjLTeS8rwKnJzUR4YNd4w%40mail.gmail.com Discussion: https://postgr.es/m/475514.1612745257%40sss.pgh.pa.us Author: Alexander Korotkov, revised by Tom Lane Reviewed-by: Tom Lane
2021-02-10Preserve pg_attribute.attstattarget across REINDEX CONCURRENTLYMichael Paquier
For an index, attstattarget can be updated using ALTER INDEX SET STATISTICS. This data was lost on the new index after REINDEX CONCURRENTLY. The update of this field is done when the old and new indexes are swapped to make the fix back-patchable. Another approach we could look after in the long-term is to change index_create() to pass the wanted values of attstattarget when creating the new relation, but, as this would cause an ABI breakage this can be done only on HEAD. Reported-by: Ronan Dunklau Author: Michael Paquier Reviewed-by: Ronan Dunklau, Tomas Vondra Discussion: https://postgr.es/m/16628084.uLZWGnKmhe@laptop-ronand Backpatch-through: 12
2021-02-08Fix permission checks on constraint violation errors on partitions.Heikki Linnakangas
If a cross-partition UPDATE violates a constraint on the target partition, and the columns in the new partition are in different physical order than in the parent, the error message can reveal columns that the user does not have SELECT permission on. A similar bug was fixed earlier in commit 804b6b6db4. The cause of the bug is that the callers of the ExecBuildSlotValueDescription() function got confused when constructing the list of modified columns. If the tuple was routed from a parent, we converted the tuple to the parent's format, but the list of modified columns was grabbed directly from the child's RTE entry. ExecUpdateLockMode() had a similar issue. That lead to confusion on which columns are key columns, leading to wrong tuple lock being taken on tables referenced by foreign keys, when a row is updated with INSERT ON CONFLICT UPDATE. A new isolation test is added for that corner case. With this patch, the ri_RangeTableIndex field is no longer set for partitions that don't have an entry in the range table. Previously, it was set to the RTE entry of the parent relation, but that was confusing. NOTE: This modifies the ResultRelInfo struct, replacing the ri_PartitionRoot field with ri_RootResultRelInfo. That's a bit risky to backpatch, because it breaks any extensions accessing the field. The change that ri_RangeTableIndex is not set for partitions could potentially break extensions, too. The ResultRelInfos are visible to FDWs at least, and this patch required small changes to postgres_fdw. Nevertheless, this seem like the least bad option. I don't think these fields widely used in extensions; I don't think there are FDWs out there that uses the FDW "direct update" API, other than postgres_fdw. If there is, you will get a compilation error, so hopefully it is caught quickly. Backpatch to 11, where support for both cross-partition UPDATEs, and unique indexes on partitioned tables, were added. Reviewed-by: Amit Langote Security: CVE-2021-3393
2021-01-30Revive "snapshot too old" with wal_level=minimal and SET TABLESPACE.Noah Misch
Given a permanent relation rewritten in the current transaction, the old_snapshot_threshold mechanism assumed the relation had never been subject to early pruning. Hence, a query could fail to report "snapshot too old" when the rewrite followed an early truncation. ALTER TABLE SET TABLESPACE is probably the only rewrite mechanism capable of exposing this bug. REINDEX sets indcheckxmin, avoiding the problem. CLUSTER has zeroed page LSNs since before old_snapshot_threshold existed, so old_snapshot_threshold has never cooperated with it. ALTER TABLE ... SET DATA TYPE makes the table look empty to every past snapshot, which is strictly worse. Back-patch to v13, where commit c6b92041d38512a4176ed76ad06f713d2e6c01a8 broke this. Kyotaro Horiguchi and Noah Misch Discussion: https://postgr.es/m/20210113.160705.2225256954956139776.horikyota.ntt@gmail.com
2021-01-30Fix CREATE INDEX CONCURRENTLY for simultaneous prepared transactions.Noah Misch
In a cluster having used CREATE INDEX CONCURRENTLY while having enabled prepared transactions, queries that use the resulting index can silently fail to find rows. Fix this for future CREATE INDEX CONCURRENTLY by making it wait for prepared transactions like it waits for ordinary transactions. This expands the VirtualTransactionId structure domain to admit prepared transactions. It may be necessary to reindex to recover from past occurrences. Back-patch to 9.5 (all supported versions). Andrey Borodin, reviewed (in earlier versions) by Tom Lane and Michael Paquier. Discussion: https://postgr.es/m/2E712143-97F7-4890-B470-4A35142ABC82@yandex-team.ru
2021-01-28Fix hash partition pruning with asymmetric partition sets.Tom Lane
perform_pruning_combine_step() was not taught about the number of partition indexes used in hash partitioning; more embarrassingly, get_matching_hash_bounds() also had it wrong. These errors are masked in the common case where all the partitions have the same modulus and no partition is missing. However, with missing or unequal-size partitions, we could erroneously prune some partitions that need to be scanned, leading to silently wrong query answers. While a minimal-footprint fix for this could be to export get_partition_bound_num_indexes and make the incorrect functions use it, I'm of the opinion that that function should never have existed in the first place. It's not reasonable data structure design that PartitionBoundInfoData lacks any explicit record of the length of its indexes[] array. Perhaps that was all right when it could always be assumed equal to ndatums, but something should have been done about it as soon as that stopped being true. Putting in an explicit "nindexes" field makes both partition_bounds_equal() and partition_bounds_copy() simpler, safer, and faster than before, and removes explicit knowledge of the number-of-partition-indexes rules from some other places too. This change also makes get_hash_partition_greatest_modulus obsolete. I left that in place in case any external code uses it, but no core code does anymore. Per bug #16840 from Michał Albrycht. Back-patch to v11 where the hash partitioning code came in. (In the back branches, add the new field at the end of PartitionBoundInfoData to minimize ABI risks.) Discussion: https://postgr.es/m/16840-571a22976f829ad4@postgresql.org
2021-01-21Fix pull_varnos' miscomputation of relids set for a PlaceHolderVar.Tom Lane
Previously, pull_varnos() took the relids of a PlaceHolderVar as being equal to the relids in its contents, but that fails to account for the possibility that we have to postpone evaluation of the PHV due to outer joins. This could result in a malformed plan. The known cases end up triggering the "failed to assign all NestLoopParams to plan nodes" sanity check in createplan.c, but other symptoms may be possible. The right value to use is the join level we actually intend to evaluate the PHV at. We can get that from the ph_eval_at field of the associated PlaceHolderInfo. However, there are some places that call pull_varnos() before the PlaceHolderInfos have been created; in that case, fall back to the conservative assumption that the PHV will be evaluated at its syntactic level. (In principle this might result in missing some legal optimization, but I'm not aware of any cases where it's an issue in practice.) Things are also a bit ticklish for calls occurring during deconstruct_jointree(), but AFAICS the ph_eval_at fields should have reached their final values by the time we need them. The main problem in making this work is that pull_varnos() has no way to get at the PlaceHolderInfos. We can fix that easily, if a bit tediously, in HEAD by passing it the planner "root" pointer. In the back branches that'd cause an unacceptable API/ABI break for extensions, so leave the existing entry points alone and add new ones with the additional parameter. (If an old entry point is called and encounters a PHV, it'll fall back to using the syntactic level, again possibly missing some valid optimization.) Back-patch to v12. The computation is surely also wrong before that, but it appears that we cannot reach a bad plan thanks to join order restrictions imposed on the subquery that the PlaceHolderVar came from. The error only became reachable when commit 4be058fe9 allowed trivial subqueries to be collapsed out completely, eliminating their join order restrictions. Per report from Stephan Springl. Discussion: https://postgr.es/m/171041.1610849523@sss.pgh.pa.us
2021-01-16Prevent excess SimpleLruTruncate() deletion.Noah Misch
Every core SLRU wraps around. With the exception of pg_notify, the wrap point can fall in the middle of a page. Account for this in the PagePrecedes callback specification and in SimpleLruTruncate()'s use of said callback. Update each callback implementation to fit the new specification. This changes SerialPagePrecedesLogically() from the style of asyncQueuePagePrecedes() to the style of CLOGPagePrecedes(). (Whereas pg_clog and pg_serial share a key space, pg_serial is nothing like pg_notify.) The bug fixed here has the same symptoms and user followup steps as 592a589a04bd456410b853d86bd05faa9432cbbb. Back-patch to 9.5 (all supported versions). Reviewed by Andrey Borodin and (in earlier versions) by Tom Lane. Discussion: https://postgr.es/m/20190202083822.GC32531@gust.leadboat.com
2021-01-14Prevent drop of tablespaces used by partitioned relationsAlvaro Herrera
When a tablespace is used in a partitioned relation (per commits ca4103025dfe in pg12 for tables and 33e6c34c3267 in pg11 for indexes), it is possible to drop the tablespace, potentially causing various problems. One such was reported in bug #16577, where a rewriting ALTER TABLE causes a server crash. Protect against this by using pg_shdepend to keep track of tablespaces when used for relations that don't keep physical files; we now abort a tablespace if we see that the tablespace is referenced from any partitioned relations. Backpatch this to 11, where this problem has been latent all along. We don't try to create pg_shdepend entries for existing partitioned indexes/tables, but any ones that are modified going forward will be protected. Note slight behavior change: when trying to drop a tablespace that contains both regular tables as well as partitioned ones, you'd previously get ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE and now you'll get ERRCODE_DEPENDENT_OBJECTS_STILL_EXIST. Arguably, the latter is more correct. It is possible to add protecting pg_shdepend entries for existing tables/indexes, by doing ALTER TABLE ONLY some_partitioned_table SET TABLESPACE pg_default; ALTER TABLE ONLY some_partitioned_table SET TABLESPACE original_tablespace; for each partitioned table/index that is not in the database default tablespace. Because these partitioned objects do not have storage, no file needs to be actually moved, so it shouldn't take more time than what's required to acquire locks. This query can be used to search for such relations: SELECT ... FROM pg_class WHERE relkind IN ('p', 'I') AND reltablespace <> 0 Reported-by: Alexander Lakhin <exclusion@gmail.com> Discussion: https://postgr.es/m/16577-881633a9f9894fd5@postgresql.org Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Reviewed-by: Michael Paquier <michael@paquier.xyz>
2021-01-06Detect the deadlocks between backends and the startup process.Fujii Masao
The deadlocks that the recovery conflict on lock is involved in can happen between hot-standby backends and the startup process. If a backend takes an access exclusive lock on the table and which finally triggers the deadlock, that deadlock can be detected as expected. On the other hand, previously, if the startup process took an access exclusive lock and which finally triggered the deadlock, that deadlock could not be detected and could remain even after deadlock_timeout passed. This is a bug. The cause of this bug was that the code for handling the recovery conflict on lock didn't take care of deadlock case at all. It assumed that deadlocks involving the startup process and backends were able to be detected by the deadlock detector invoked within backends. But this assumption was incorrect. The startup process also should have invoked the deadlock detector if necessary. To fix this bug, this commit makes the startup process invoke the deadlock detector if deadlock_timeout is reached while handling the recovery conflict on lock. Specifically, in that case, the startup process requests all the backends holding the conflicting locks to check themselves for deadlocks. Back-patch to v9.6. v9.5 has also this bug, but per discussion we decided not to back-patch the fix to v9.5. Because v9.5 doesn't have some infrastructure codes (e.g., 37c54863cf) that this bug fix patch depends on. We can apply those codes for the back-patch, but since the next minor version release is the final one for v9.5, it's risky to do that. If we unexpectedly introduce new bug to v9.5 by the back-patch, there is no chance to fix that. We determined that the back-patch to v9.5 would give more risk than gain. Author: Fujii Masao Reviewed-by: Bertrand Drouvot, Masahiko Sawada, Kyotaro Horiguchi Discussion: https://postgr.es/m/4041d6b6-cf24-a120-36fa-1294220f8243@oss.nttdata.com
2020-12-28Fix assorted issues in backend's GSSAPI encryption support.Tom Lane
Unrecoverable errors detected by GSSAPI encryption can't just be reported with elog(ERROR) or elog(FATAL), because attempting to send the error report to the client is likely to lead to infinite recursion or loss of protocol sync. Instead make this code do what the SSL encryption code has long done, which is to just report any such failure to the server log (with elevel COMMERROR), then pretend we've lost the connection by returning errno = ECONNRESET. Along the way, fix confusion about whether message translation is done by pg_GSS_error() or its callers (the latter should do it), and make the backend version of that function work more like the frontend version. Avoid allocating the port->gss struct until it's needed; we surely don't need to allocate it in the postmaster. Improve logging of "connection authorized" messages with GSS enabled. (As part of this, I back-patched the code changes from dc11f31a1.) Make BackendStatusShmemSize() account for the GSS-related space that will be allocated by CreateSharedBackendStatus(). This omission could possibly cause out-of-shared-memory problems with very high max_connections settings. Remove arbitrary, pointless restriction that only GSS authentication can be used on a GSS-encrypted connection. Improve documentation; notably, document the fact that libpq now prefers GSS encryption over SSL encryption if both are possible. Per report from Mikael Gustavsson. Back-patch to v12 where this code was introduced. Discussion: https://postgr.es/m/e5b0b6ed05764324a2f3fe7acfc766d5@smhi.se
2020-12-24Fix race condition between shutdown and unstarted background workers.Tom Lane
If a database shutdown (smart or fast) is commanded between the time some process decides to request a new background worker and the time that the postmaster can launch that worker, then nothing happens because the postmaster won't launch any bgworkers once it's exited PM_RUN state. This is fine ... unless the requesting process is waiting for that worker to finish (or even for it to start); in that case the requestor is stuck, and only manual intervention will get us to the point of being able to shut down. To fix, cancel pending requests for workers when the postmaster sends shutdown (SIGTERM) signals, and similarly cancel any new requests that arrive after that point. (We can optimize things slightly by only doing the cancellation for workers that have waiters.) To fit within the existing bgworker APIs, the "cancel" is made to look like the worker was started and immediately stopped, causing deregistration of the bgworker entry. Waiting processes would have to deal with premature worker exit anyway, so this should introduce no bugs that weren't there before. We do have a side effect that registration records for restartable bgworkers might disappear when theoretically they should have remained in place; but since we're shutting down, that shouldn't matter. Back-patch to v10. There might be value in putting this into 9.6 as well, but the management of bgworkers is a bit different there (notably see 8ff518699) and I'm not convinced it's worth the effort to validate the patch for that branch. Discussion: https://postgr.es/m/661570.1608673226@sss.pgh.pa.us
2020-12-21Disallow SRFs when considering sorts below Gather MergeTomas Vondra
While we do allow SRFs in ORDER BY, scan/join processing should not consider such cases - such sorts should only happen via final Sort atop a ProjectSet. So make sure we don't try adding such sorts below Gather Merge, just like we do for expressions that are volatile and/or not parallel safe. Backpatch to PostgreSQL 13, where this code was introduced as part of the Incremental Sort patch. Author: James Coleman Reviewed-by: Tomas Vondra Backpatch-through: 13 Discussion: https://postgr.es/m/CAAaqYe8cK3g5CfLC4w7bs=hC0mSksZC=H5M8LSchj5e5OxpTAg@mail.gmail.com Discussion: https://postgr.es/m/295524.1606246314%40sss.pgh.pa.us
2020-12-21Check parallel safety in generate_useful_gather_pathsTomas Vondra
Commit ebb7ae839d ensured we ignore pathkeys with volatile expressions when considering adding a sort below a Gather Merge. Turns out we need to care about parallel safety of the pathkeys too, otherwise we might try sorting e.g. on results of a correlated subquery (as demonstrated by a report from Luis Roberto). Initial investigation by Tom Lane, patch by James Coleman. Backpatch to 13, where the code was instroduced (as part of Incremental Sort). Reported-by: Luis Roberto Author: James Coleman Reviewed-by: Tomas Vondra Backpatch-through: 13 Discussion: https://postgr.es/m/622580997.37108180.1604080457319.JavaMail.zimbra%40siscobra.com.br Discussion: https://postgr.es/m/CAAaqYe8cK3g5CfLC4w7bs=hC0mSksZC=H5M8LSchj5e5OxpTAg@mail.gmail.com
2020-12-01Ensure that expandTableLikeClause() re-examines the same table.Tom Lane
As it stood, expandTableLikeClause() re-did the same relation_openrv call that transformTableLikeClause() had done. However there are scenarios where this would not find the same table as expected. We hold lock on the LIKE source table, so it can't be renamed or dropped, but another table could appear before it in the search path. This explains the odd behavior reported in bug #16758 when cloning a table as a temp table of the same name. This case worked as expected before commit 502898192 introduced the need to open the source table twice, so we should fix it. To make really sure we get the same table, let's re-open it by OID not name. That requires adding an OID field to struct TableLikeClause, which is a little nervous-making from an ABI standpoint, but as long as it's at the end I don't think there's any serious risk. Per bug #16758 from Marc Boeren. Like the previous patch, back-patch to all supported branches. Discussion: https://postgr.es/m/16758-840e84a6cfab276d@postgresql.org
2020-11-30Fix missing outfuncs.c support for IncrementalSortPath.Tom Lane
For debugging purposes, Path nodes are supposed to have outfuncs support, but this was overlooked in the original incremental sort patch. While at it, clean up a couple other minor oversights, as well as bizarre choice of return type for create_incremental_sort_path(). (All the existing callers just cast it to "Path *" immediately, so they don't care, but some future caller might care.) outfuncs.c fix by Zhijie Hou, the rest by me Discussion: https://postgr.es/m/324c4d81d8134117972a5b1f6cdf9560@G08CNEXMBPEKD05.g08.fujitsu.local
2020-11-24Properly check index mark/restore in ExecSupportsMarkRestore.Andrew Gierth
Previously this code assumed that all IndexScan nodes supported mark/restore, which is not true since it depends on optional index AM support functions. This could lead to errors about missing support functions in rare edge cases of mergejoins with no sort keys, where an unordered non-btree index scan was placed on the inner path without a protecting Materialize node. (Normally, the fact that merge join requires ordered input would avoid this error.) Backpatch all the way since this bug is ancient. Per report from Eugen Konkov on irc. Discussion: https://postgr.es/m/87o8jn50be.fsf@news-spur.riddles.org.uk
2020-11-10Fix and simplify some usages of TimestampDifference().Tom Lane
Introduce TimestampDifferenceMilliseconds() to simplify callers that would rather have the difference in milliseconds, instead of the select()-oriented seconds-and-microseconds format. This gets rid of at least one integer division per call, and it eliminates some apparently-easy-to-mess-up arithmetic. Two of these call sites were in fact wrong: * pg_prewarm's autoprewarm_main() forgot to multiply the seconds by 1000, thus ending up with a delay 1000X shorter than intended. That doesn't quite make it a busy-wait, but close. * postgres_fdw's pgfdw_get_cleanup_result() thought it needed to compute microseconds not milliseconds, thus ending up with a delay 1000X longer than intended. Somebody along the way had noticed this problem but misdiagnosed the cause, and imposed an ad-hoc 60-second limit rather than fixing the units. This was relatively harmless in context, because we don't care that much about exactly how long this delay is; still, it's wrong. There are a few more callers of TimestampDifference() that don't have a direct need for seconds-and-microseconds, but can't use TimestampDifferenceMilliseconds() either because they do need microsecond precision or because they might possibly deal with intervals long enough to overflow 32-bit milliseconds. It might be worth inventing another API to improve that, but that seems outside the scope of this patch; so those callers are untouched here. Given the fact that we are fixing some bugs, and the likelihood that future patches might want to back-patch code that uses this new API, back-patch to all supported branches. Alexey Kondratov and Tom Lane Discussion: https://postgr.es/m/3b1c053a21c07c1ed5e00be3b2b855ef@postgrespro.ru