As reported by Noah, it's possible, although practically very unlikely, that
interrupts could be processed in between pgaio_io_reopen() and
pgaio_io_perform_synchronously(). Prevent that by explicitly holding
interrupts.
It also seems good to add an assertion to pgaio_io_before_prep() to ensure
that interrupts are held, as otherwise FDs referenced by the IO could be
closed during interrupt processing. All code in the aio series currently runs
the code with interrupts held, but it seems better to be paranoid.
Reviewed-by: Noah Misch <noah@leadboat.com>
Reported-by: Noah Misch <noah@leadboat.com>
Discussion: https://postgr.es/m/20250324002939.5c.nmisch@google.com
The brin_bloom_union() function combines two BRIN summaries, by merging
one filter into the other. With bloom, we have to decompress the filters
first, but the function failed to update the summary to store the merged
filter. As a consequence, the index may be missing some of the data, and
return false negatives.
This issue exists since BRIN bloom indexes were introduced in Postgres
14, but at that point the union function was called only when two
sessions happened to summarize a range concurrently, which is rare. It
got much easier to hit in 17, as parallel builds use the union function
to merge summaries built by workers.
Fixed by storing a pointer to the decompressed filter, and freeing the
original one. Free the second filter too, if it was decompressed. The
freeing is not strictly necessary, because the union is called in
short-lived contexts, but it's tidy.
Backpatch to 14, where BRIN bloom indexes were introduced.
Reported by Arseniy Mukhin, investigation and fix by me.
Reported-by: Arseniy Mukhin
Discussion: https://postgr.es/m/18855-1cf1c8bcc22150e6%40postgresql.org
Backpatch-through: 14
It seems potentially useful to label our shared libraries with version
information, now that a facility exists for retrieving that. This
patch labels them with the PG_VERSION string. There was some
discussion about using semantic versioning conventions, but that
doesn't seem terribly helpful for modules with no SQL-level presence;
and for those that do have SQL objects, we typically expect them
to support multiple revisions of the SQL definitions, so it'd still
not be very helpful.
I did not label any of src/test/modules/. It seems unnecessary since
we don't install those, and besides there ought to be someplace that
still provides test coverage for the original PG_MODULE_MAGIC macro.
Author: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/dd4d1b59-d0fe-49d5-b28f-1e463b68fa32@gmail.com
This macro allows dynamically loaded shared libraries (modules) to
provide a wired-in module name and version, and possibly other
compile-time-constant fields in future. This information can be
retrieved with the new pg_get_loaded_modules() function.
This feature is expected to be particularly useful for modules
that do not have any exposed SQL functionality and thus are
not associated with a SQL-level extension object. But even for
modules that do belong to extensions, being able to verify the
actual code version can be useful.
Author: Andrei Lepikhov <lepihov@gmail.com>
Reviewed-by: Yurii Rashkovskii <yrashk@omnigres.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/dd4d1b59-d0fe-49d5-b28f-1e463b68fa32@gmail.com
custom_query_jumble (introduced in 5ac462e2b7 as a node field
attribute) is now assigned to the expanded reference name "eref" of
RangeTblEntry, adding in the query jumble computation the non-qualified
aliased relation name, without the list of column names. The relation
OID is removed from the query jumbling.
The effects of this change can be seen in the tests added by
3430215fe3, where pg_stat_statements (PGSS) entries are now grouped
using the relation name, ignoring the relation search_path may point at.
For example, these two relations are different, but are now grouped in a
single PGSS entry as they are assigned the same query ID:
CREATE TABLE foo1.tab (a int);
CREATE TABLE foo2.tab (b int);
SET search_path = 'foo1';
SELECT count(*) FROM tab;
SET search_path = 'foo2';
SELECT count(*) FROM tab;
SELECT count(*) FROM foo1.tab;
SELECT count(*) FROM foo2.tab;
SELECT query, calls FROM pg_stat_statements WHERE query ~ 'FROM tab';
query | calls
--------------------------+-------
SELECT count(*) FROM tab | 4
(1 row)
It is still possible to use an alias in the FROM clause to split these.
This behavior is useful for relations re-created with the same name,
where queries based on such relations would be grouped in the same
PGSS entry. For permanent schemas, it should not really matter in
practice. The main benefit is for workloads that use a lot of temporary
relations, which are usually re-created with the same name continuously.
These can be a heavy source of bloat in PGSS depending on the workload.
Such entries can now be grouped together, improving the user experience.
The original idea from Christoph Berg used catalog lookups to find
temporary relations, something that the query jumble has never done, and
it could cause some performance regressions. The idea to use
RangeTblEntry.eref and the relation name, applying the same rules for
all relations, temporary and not temporary, has been proposed by Tom
Lane. The documentation additions have been suggested by Sami Imseih.
Author: Michael Paquier <michael@paquier.xyz>
Co-authored-by: Sami Imseih <samimseih@gmail.com>
Reviewed-by: Christoph Berg <myon@debian.org>
Reviewed-by: Lukas Fittl <lukas@fittl.com>
Reviewed-by: Sami Imseih <samimseih@gmail.com>
Discussion: https://postgr.es/m/Z9iWXKGwkm8RAC93@msg.df7cb.de
A node field marked with custom_query_jumble and query_jumble_ignore
would generate some code of a custom routine. The script is changed so
as custom_query_jumble behaves like the other options in this case,
query_jumble_ignore taking priority, with no code generated.
A comment related to the code generated for node types was misplaced.
Thinkos introduced in 5ac462e2b7.
Reported-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/1324036.1742945060@sss.pgh.pa.us
For import and export, use schemaname/relname rather than
regclass.
This is more natural during export, fits with the other arguments
better, and it gives better control over error handling in case we
need to downgrade more errors to warnings.
Also, use text for the argument types for schemaname, relname, and
attname so that casts to "name" are not required.
Author: Corey Huinker <corey.huinker@gmail.com>
Discussion: https://postgr.es/m/CADkLM=ceOSsx_=oe73QQ-BxUFR2Cwqum7-UP_fPe22DBY0NerA@mail.gmail.com
Split ATExecAlterConstraintInternal() into two functions:
ATExecAlterConstrDeferrability() and
ATExecAlterConstrInheritability(). This simplifies the code and
avoids unnecessary confusion caused by recursive code, which isn't
needed for ATExecAlterConstrInheritability().
(This also takes over the changes in commit 64224a834c, as the new
AlterConstrDeferrabilityRecurse() is essentially the old
ATExecAlterChildConstr().)
Author: Amul Sul <amul.sul@enterprisedb.com>
Discussion: https://www.postgresql.org/message-id/flat/CAAJ_b962c5AcYW9KUt_R_ER5qs3fUGbe4az-SP-vuwPS-w-AGA@mail.gmail.com
Small fixes for commit f4e53e10b6: Add missing calls to
InvokeObjectPostAlterHook() and also CacheInvalidateRelcache(). The
former change could have a user-visible effect. The latter omission
might have caused other bugs, but it is not clear whether one actually
existed. With these changes, the code is now more consistent with
similar ALTER CONSTRAINT variants, especially the ones that set the
deferrability.
Reviewed-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://postgr.es/m/CAF1DzPVfOW6Kk=7SSh7LbneQDJWh=PbJrEC_Wkzc24tHOyQWGg@mail.gmail.com
This option gives the possibility for query jumble to define a custom
routine for the field of a Node, extending support for
custom_query_jumble as a node field attribute. When dealing with
complex node structures, this can be simpler than having to enforce a
custom function across a full node.
Custom functions need to be defined in queryjumblefuncs.c, named as
_jumble${node}_${field}(), and use in input the JumbleState, the node
and its field. The field is not really required if we have the Node,
but it makes custom implementations somewhat easier to think about. The
code generated by gen_node_support.pl uses a macro called
JUMBLE_CUSTOM(), hiding the internals of the logic inside
queryjumblefuncs.c.
This will be used by an upcoming patch manipulating adding a custom
routine into a field of RangeTblEntry, but this facility can become
useful in more cases.
Reviewed-by: Christoph Berg <myon@debian.org>
Discussion: https://postgr.es/m/Z9y43-dRvb4EtxQ0@paquier.xyz
The entries aren't freed until the entire hash table is destroyed, so
use the Bump allocator to improve allocation speed, avoid wasting
space on the chunk header, and avoid wasting space due to the
power-of-two allocations.
Discussion: https://postgr.es/m/CAApHDvqv1aNB4cM36FzRwivXrEvBO_LsG_eQ3nqDXTjECaatOQ@mail.gmail.com
Reviewed-by: David Rowley
Until now max_files_per_process=N limited each backend to open N files in
total (minus a safety factor), even if there were already more files opened in
postmaster and inherited by backends. Change max_files_per_process to control
how many additional files each process is allowed to open.
The main motivation for this is the patch to add io_method=io_uring, which
needs to open one file for each backend. Without this patch, even if
RLIMIT_NOFILE is high enough, postmaster will fail in set_max_safe_fds() if
started with a high max_connections. The cause of the failure is that, until
now, set_max_safe_fds() subtracted the already open files from
max_files_per_process.
Reviewed-by: Noah Misch <noah@leadboat.com>
Discussion: https://postgr.es/m/w6uiicyou7hzq47mbyejubtcyb2rngkkf45fk4q7inue5kfbeo@bbfad3qyubvs
Discussion: https://postgr.es/m/CAGECzQQh6VSy3KG4pN1d=h9J=D1rStFCMR+t7yh_Kwj-g87aLQ@mail.gmail.com
The bitmap heap scan skip fetch optimization skips fetching the heap
block when a page is set all-visible in the visibility map and no
columns from the table are needed to satisfy the query.
2b73a8cd33 and c3953226a0 changed the control flow of bitmap heap scan
to use the read stream API. The read stream API returns buffers
containing blocks to the user. To make this work with the skip fetch
optimization, we keep a count of the empty tuples we need to emit for
all the blocks skipped and only emit the empty tuples after processing
the next block fetched from the heap or at the end of the scan.
It's incorrect to recheck NULL tuples, so we must set `recheck` to false
before yielding control back to BitmapHeapNext(). This was done before
emitting any remaining empty tuples at the end of the scan but not for
empty tuples emitted during the scan. This meant that if a page fetched
from the heap did require recheck and set `recheck` to true and then we
emitted empty tuples for subsequent blocks, we would get wrong results.
Fix this by always setting `recheck` to false before emitting empty
tuples.
Reported-by: Alexander Lakhin <exclusion@gmail.com>
Tested-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/496f7acd-881c-4df3-9bd3-8f8534dfec26%40gmail.com
Introduce a new conflict type, multiple_unique_conflicts, to handle cases
where an incoming row during logical replication violates multiple UNIQUE
constraints.
Previously, the apply worker detected and reported only the first
encountered key conflict (insert_exists/update_exists), causing repeated
failures as each constraint violation needs to be handled one by one
making the process slow and error-prone.
With this patch, the apply worker checks all unique constraints upfront
once the first key conflict is detected and reports
multiple_unique_conflicts if multiple violations exist. This allows users
to resolve all conflicts at once by deleting all conflicting tuples rather
than dealing with them individually or skipping the transaction.
In the future, this will also allow us to specify different resolution
handlers for such a conflict type.
Add the stats for this conflict type in pg_stat_subscription_stats.
Author: Nisha Moond <nisha.moond412@gmail.com>
Author: Zhijie Hou <houzj.fnst@fujitsu.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Reviewed-by: Peter Smith <smithpb2250@gmail.com>
Reviewed-by: Dilip Kumar <dilipbalaut@gmail.com>
Discussion: https://postgr.es/m/CABdArM7FW-_dnthGkg2s0fy1HhUB8C3ELA0gZX1kkbs1ZZoV3Q@mail.gmail.com
This field can be optionally set in a PlannedStmt through the planner
hook, giving extensions the possibility to assign an identifier related
to a computed plan. The backend is changed to report it in the backend
entry of a process running (including the extended query protocol), with
semantics and APIs to set or get it similar to what is used for the
existing query ID (introduced in the backend via 4f0b0966c8). The plan
ID is reset at the same timing as the query ID. Currently, this
information is not added to the system view pg_stat_activity; extensions
can access it through PgBackendStatus.
Some patches have been proposed to provide some features in the planning
area, where a plan identifier is used as a key to know the plan involved
(for statistics, plan storage and manipulations, etc.), and the point of
this commit is to provide an anchor in the backend that extensions can
rely on for future work. The reset of the plan identifier is
controlled by core and follows the same pattern as the query identifier
added in 4f0b0966c8.
The contents of this commit are extracted from a larger set proposed
originally by Lukas Fittl, that Sami Imseih has proposed as an
independent change, with a few tweaks sprinkled by me.
Author: Lukas Fittl <lukas@fittl.com>
Author: Sami Imseih <samimseih@gmail.com>
Reviewed-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/CAP53Pkyow59ajFMHGpmb1BK9WHDypaWtUsS_5DoYUEfsa_Hktg@mail.gmail.com
Discussion: https://postgr.es/m/CAA5RZ0vyWd4r35uUBUmhngv8XqeiJUkJDDKkLf5LCoWxv-t_pw@mail.gmail.com
During hot standby, ExpireAllKnownAssignedTransactionIds() and
ExpireOldKnownAssignedTransactionIds() functions mark old transactions
as no-longer running, but they failed to update xactCompletionCount
and latestCompletedXid. AFAICS it would not lead to incorrect query
results, because those functions effectively turn in-progress
transactions into aborted transactions and an MVCC snapshot considers
both as "not visible". But it could surprise GetSnapshotDataReuse()
and trigger the "TransactionIdPrecedesOrEquals(TransactionXmin,
RecentXmin))" assertion in it, if the apparent xmin in a backend would
move backwards. We saw this happen when GetCatalogSnapshot() would
reuse an older catalog snapshot, when GetTransactionSnapshot() had
already advanced TransactionXmin.
The bug goes back all the way to commit 623a9ba79b in v14 that
introduced the snapshot reuse mechanism, but it started to happen more
frequently with commit 952365cded which removed a
GetTransactionSnapshot() call from backend startup. That made it more
likely for ExpireOldKnownAssignedTransactionIds() to be called between
GetCatalogSnapshot() and the first GetTransactionSnapshot() in a
backend.
Andres Freund first spotted this assertion failure on buildfarm member
'skink'. Reproduction and analysis by Tomas Vondra.
Backpatch-through: 14
Discussion: https://www.postgresql.org/message-id/oey246mcw43cy4qw2hqjmurbd62lfdpcuxyqiu7botx3typpax%40h7o7mfg5zmdj
Add a new scheduling heuristic: don't end the ongoing primitive index
scan immediately (at the point where _bt_advance_array_keys notices that
the next set of matching tuples must be on a later page) if the primscan
already managed to step right/left from its first leaf page. Schedule a
recheck against the next sibling leaf page's finaltup instead.
The new heuristic tends to avoid scenarios where the top-level scan
repeatedly starts and ends primitive index scans that each read only one
leaf page from a group of neighboring leaf pages. Affected top-level
scans will now tend to step forward (or backward) through the index
instead, without wasting cycles on descending the index anew.
The recheck mechanism isn't exactly new. But up until now it has only
been used to deal with edge cases involving high key finaltups with one
or more truncated -inf attributes that _bt_advance_array_keys deemed
"provisionally satisfied" (satisfied for the purposes of allowing the
scan to step onto the next page, subject to recheck once on that page).
The mechanism was added by commit 5bf748b8, which invented the general
concept of primitive scan scheduling. It was later enhanced by commit
79fa7b3b, which taught it about cases involving -inf attributes that
satisfy inequality scan keys required in the opposite-to-scan direction
only (arguably, they should have been covered by the earliest version).
Now the recheck mechanism can be applied based on scan-level heuristics,
which have nothing to do with truncated high keys. Now rechecks might
be performed by _bt_readpage when scanning in _either_ scan direction.
The theory behind the new heuristic is that any primitive scan that
makes it past its first leaf page is one that is already likely to have
arrays whose key values match index tuples that are closely clustered
together in the index. The rules that determine whether we ever get
past the first page are still conservative (that'll still only happen
when pstate.finaltup strongly suggests that it's the right thing to do).
Surviving past the first leaf page is a strong signal in itself.
Preparation for an upcoming patch that will add skip scan optimizations
to nbtree. That'll work by adding skip arrays, which behave similarly
to SAOP arrays, but generate their elements procedurally and on-demand.
Note that this commit isn't specifically concerned with skip arrays; the
scheduling logic doesn't (and won't) condition anything on whether the
scan uses skip arrays, SAOP arrays, or some combination of the two
(which seems like a good general principle for _bt_advance_array_keys).
While the problems that this commit ameliorates are more likely with
skip arrays (at least in practice), SAOP arrays (or those with very
dense, contiguous array elements) are also affected.
Author: Peter Geoghegan <pg@bowt.ie>
Reviewed-By: Matthias van de Meent <boekewurm+postgres@gmail.com>
Discussion: https://postgr.es/m/CAH2-Wzkz0wPe6+02kr+hC+JJNKfGtjGTzpG3CFVTQmKwWNrXNw@mail.gmail.com
Like 69273b818b did for GiST vacuuming, make SP-GiST vacuum use the
read stream API for vacuuming physically contiguous index pages.
Concurrent insertions may cause SP-GiST index tuples to be redirected.
While vacuuming, these are added to a pending list which is later
processed to ensure no dead tuples are left behind. Pages containing
such tuples are still read by directly calling ReadBuffer() and do not
use the read stream API.
Author: Andrey M. Borodin <x4mmm@yandex-team.ru>
Reviewed-by: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://postgr.es/m/37432403-8657-403B-9CDF-5A642BECDD81%40yandex-team.ru
This code must have missed a memo about the backend type description
being supplied automatically these days, and was duplicating that
information.
Before: "io worker io worker: N"
After: "io worker N"
This commit introduces a new GUC option max_active_replication_origins
to control the maximum number of active replication
origins. Previously, this was controlled by
'max_replication_slots'. Having a separate GUC option provides better
flexibility for setting up subscribers, as they may not require
replication slots (for cascading replication) but always require
replication origins.
Author: Euler Taveira <euler@eulerto.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Reviewed-by: vignesh C <vignesh21@gmail.com>
Discussion: https://postgr.es/m/b81db436-8262-4575-b7c4-bc0c1551000b@app.fastmail.com
Make genbki.pl emit some boilerplate comments identifying the
sections of the pg_*_d.h files that it generates. This is in
hopes of making them slightly more readable, in case people
look at those files and not the pg_*.h/pg_*.dat originals.
Discussion: https://postgr.es/m/1134562.1742507765@sss.pgh.pa.us
Like c5c239e26e did for btree vacuuming, make GiST vacuum use the
read stream API for sequentially processed pages.
Because it is possible for concurrent insertions to relocate unprocessed
index entries to already vacuumed pages, GiST vacuum must backtrack and
reprocess those pages. These pages are still read with explicit
ReadBuffer() calls.
Author: Andrey M. Borodin <x4mmm@yandex-team.ru>
Reviewed-by: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://postgr.es/m/EFEBED92-18D1-4C0F-A4EB-CD47072EF071%40yandex-team.ru
c5c239e26e made btree vacuum use the read stream API. Though it used
functions declared in read_stream.h, it relied on transitively including
it. Explicitly include that file. Also remove an extraneous newline and
decrease the scope of one of the local variables in btvacuumscan().
Btree vacuum processes all index pages in physical order. Now it uses
the read stream API to get the next buffer instead of explicitly
invoking ReadBuffer().
It is possible for concurrent insertions to cause page splits during
index vacuuming. This can lead to index entries that have yet to be
vacuumed being moved to pages that have already been vacuumed. Btree
vacuum code handles this by backtracking to reprocess those pages. So,
while sequentially encountered pages are now read through the
read stream API, backtracked pages are still read with explicit
ReadBuffer() calls.
Author: Andrey Borodin <x4mmm@yandex-team.ru>
Reviewed-by: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Junwang Zhao <zhjwpku@gmail.com>
Reviewed-by: Kirill Reshke <reshkekirill@gmail.com>
Discussion: https://postgr.es/m/flat/CAAKRu_bW1UOyup%3DjdFw%2BkOF9bCaAm%3D9UpiyZtbPMn8n_vnP%2Big%40mail.gmail.com#3b3a84132fc683b3ee5b40bc4c2ea2a5
StartReadBuffers() reports a short read when it finds a cached block
that ends a range needing I/O by updating the caller's *nblocks. It
doesn't want to have to unpin the trailing hit that it knows the caller
wants, so the v17 version used sleight of hand in the name of
simplicity: it included it in *nblocks as if it were part of the I/O,
but internally tracked the shorter real I/O size in io_buffers_len (now
removed).
This API change "forwards" the delimiting buffer to the next call. It's
still pinned, and still stored in the caller's array, but *nblocks no
longer includes stray buffers that are not really part of the operation.
The expectation is that the caller still wants the rest of the blocks
and will call again starting from that point, and now it can pass the
already pinned buffer back in (or choose not to and release it).
The change is needed for the coming asynchronous I/O version's larger
version of the problem: by definition it must move BM_IO_IN_PROGRESS
negotiation from WaitReadBuffers() to StartReadBuffers(), but it might
already have many buffers pinned before it discovers a need to split an
I/O. (The current synchronous I/O version hides that detail from
callers by looping over smaller reads if required to make all covered
buffers valid in WaitReadBuffers(), so it looks like one operation but
it might occasionally be several under the covers.)
Aside from avoiding unnecessary pin traffic, this will also be important
for later work on out-of-order streams: you can't prioritize data that
is already available right now if that fact is hidden from you.
The new API is natural for read_stream.c (see ed0b87ca). After a short
read it leaves forwarded buffers where they fell in its circular queue
for the continuing call to pick up.
Single-block StartReadBuffer() and traditional ReadBuffer() share code
but are not affected by the change. They don't do multi-block I/O.
Reviewed-by: Andres Freund <andres@anarazel.de> (earlier versions)
Discussion: https://postgr.es/m/CA%2BhUKGK_%3D4CVmMHvsHjOVrK6t4F%3DLBpFzsrr3R%2BaJYN8kcTfWg%40mail.gmail.com
In preparation for a follow-up change to the buffer manager, teach
read_stream.c to manage buffers "forwarded" from one StartReadBuffers()
call to the next after a short read. This involves a small amount of
extra book-keeping, and opens the way for lower levels to split I/O
operations without having to drop pins, as required for efficient
handling of various edge cases.
Concretely, the "buffers" argument will change from an out parameter to
an in/out parameter. Buffer queue elements must be initialized on first
use and cleared after they're consumed, but forwarded buffers are left
where they fall ahead of the current pending read in the queue, ready
for use by the operation that continues where a short read left off.
The stream also needs to count them for pin limit management and release
them on reset/early end.
Tested-by: Andres Freund <andres@anarazel.de> (earlier versions)
Discussion: https://postgr.es/m/CA%2BhUKGK_%3D4CVmMHvsHjOVrK6t4F%3DLBpFzsrr3R%2BaJYN8kcTfWg%40mail.gmail.com
This removes a needless special case for Memoize's FORMAT TEXT EXPLAIN
output.
ExplainPropertyText() outputs the same thing in text mode as the
special-case code was doing, so removing the special-case code results in
the same EXPLAIN output, just with less code.
It seems like a good idea to fix this to help prevent future changes in
this area from copying the same pattern.
Author: Ilia Evdokimov <ilya.evdokimov@tantorlabs.com>
Reported-by: David Rowley <dgrowleyml@gmail.com>
Discussion: https://postgr.es/m/88a71bcd-0b5c-4d0b-8107-757e96f402d5@tantorlabs.com
Previously we would have the following inaccuracies when a backend tried to
read in a buffer, but that buffer was read in concurrently by another backend:
- the read IO was double-counted in the global buffer access stats (pgBufferUsage)
- the buffer hit was not accounted for in:
- global buffer access statistics
- pg_stat_io
- relation level IO stats
- vacuum cost balancing
While trying to read in a buffer that is concurrently read in by another
backend is not a common occurrence, it's also not that rare, e.g. due to
concurrent sequential scans on the same relation. This scenario has become
more likely in PG 17, due to the introducing of read streams, which can pin
multiple buffers before calling StartBufferIO() for all the buffers.
This behaviour has historically grown, but there doesn't seem to be any reason
to continue with the wrong accounting.
Reviewed-by: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://postgr.es/m/CAAKRu_Zk-B08AzPsO-6680LUHLOCGaNJYofaxTFseLa=OepV1g@mail.gmail.com
We need to hold interrupts across most of the smgr.c/md.c functions, as
otherwise interrupt processing, e.g. due to a < ERROR elog/ereport, can
trigger procsignal processing, which in turn can trigger smgrreleaseall(). As
the relevant code is not reentrant, we quickly end up in a bad situation.
The only reason we haven't noticed this before is that there is only one
non-error ereport called in affected routines, in register_dirty_segments(),
and that one is extremely rarely reached. If one enables fd.c's FDDEBUG it's
easy to reproduce crashes.
It seems better to put the HOLD_INTERRUPTS()/RESUME_INTERRUPTS() in smgr.c,
instead of trying to push them down to md.c where possible: For one, every
smgr implementation would be vulnerable, for another, a good bit of smgr.c
code itself is affected too.
Eventually we might want a more targeted solution, allowing e.g. a networked
smgr implementation to be interrupted, but many other, more complicated,
problems would need to be fixed for that to be viable (e.g. smgr.c is often
called with interrupts already held).
One could argue this should be backpatched, but the existing < ERROR
elog/ereports that can be reached with unmodified sources are unlikely to be
reached. On balance the risk of backpatching seems higher than the gain - at
least for now.
Reviewed-by: Noah Misch <noah@leadboat.com>
Reviewed-by: Thomas Munro <thomas.munro@gmail.com>
Discussion: https://postgr.es/m/3vae7l5ozvqtxmd7rr7zaeq3qkuipz365u3rtim5t5wdkr6f4g@vkgf2fogjirl
This new parameter works just like the storage parameter of the
same name: if set to true (which is the default), autovacuum and
VACUUM attempt to truncate any empty pages at the end of the table.
It is primarily intended to help users avoid locking issues on hot
standbys. The setting can be overridden with the storage parameter
or VACUUM's TRUNCATE option.
Since there's presently no way to determine whether a Boolean
storage parameter is explicitly set or has just picked up the
default value, this commit also introduces an isset_offset member
to relopt_parse_elt.
Suggested-by: Will Storey <will@summercat.com>
Author: Nathan Bossart <nathandbossart@gmail.com>
Co-authored-by: Gurjeet Singh <gurjeet@singh.im>
Reviewed-by: Laurenz Albe <laurenz.albe@cybertec.at>
Reviewed-by: Fujii Masao <masao.fujii@oss.nttdata.com>
Reviewed-by: Robert Treat <rob@xzilla.net>
Discussion: https://postgr.es/m/Z2DE4lDX4tHqNGZt%40dev.null
The comment explained that ALTER TABLE ADD CONSTRAINT USING INDEX is
only supported with a btree index. (This is not being changed.) The
reason is to keep upgrades robust, as explained there. The other part
of the comment, that btree is the only unique index kind anyway, is
somewhat less true as we're trying to enable unique indexes other than
btree, and it's irrelevant to this check. There is a check for
indisunique earlier already. So just remove this part of the comment.
Author: Mark Dilger <mark.dilger@enterprisedb.com>
Discussion: https://www.postgresql.org/message-id/flat/E72EAA49-354D-4C2E-8EB9-255197F55330@enterprisedb.com
The new GUC extension_control_path specifies a path to look for
extension control files. The default value is $system, which looks in
the compiled-in location, as before.
The path search uses the same code and works in the same way as
dynamic_library_path.
Some use cases of this are: (1) testing extensions during package
builds, (2) installing extensions outside security-restricted
containers like Python.app (on macOS), (3) adding extensions to
PostgreSQL running in a Kubernetes environment using operators such as
CloudNativePG without having to rebuild the base image for each new
extension.
There is also a tweak in Makefile.global so that it is possible to
install extensions using PGXS into an different directory than the
default, using 'make install prefix=/else/where'. This previously
only worked when specifying the subdirectories, like 'make install
datadir=/else/where/share pkglibdir=/else/where/lib', for purely
implementation reasons. (Of course, without the path feature,
installing elsewhere was rarely useful.)
Author: Peter Eisentraut <peter@eisentraut.org>
Co-authored-by: Matheus Alcantara <matheusssilv97@gmail.com>
Reviewed-by: David E. Wheeler <david@justatheory.com>
Reviewed-by: Gabriele Bartolini <gabriele.bartolini@enterprisedb.com>
Reviewed-by: Marco Nenciarini <marco.nenciarini@enterprisedb.com>
Reviewed-by: Niccolò Fei <niccolo.fei@enterprisedb.com>
Discussion: https://www.postgresql.org/message-id/flat/E7C7BFFB-8857-48D4-A71F-88B359FADCFD@justatheory.com
Commit cbc127917e introduced tracking of unpruned relids to avoid
processing pruned relations, and changed ExecInitModifyTable() to
initialize only unpruned result relations. As a result, MERGE
statements that prune all target partitions can now lead to crashes
or incorrect behavior during execution.
The crash occurs because some executor code paths rely on
ModifyTableState.resultRelInfo[0] being present and initialized,
even when no result relations remain after pruning. For example,
ExecMerge() and ExecMergeNotMatched() use the first resultRelInfo
to determine the appropriate action. Similarly,
ExecInitPartitionInfo() assumes that at least one result relation
exists.
To preserve these assumptions, ExecInitModifyTable() now includes the
first result relation in the initialized result relation list if all
result relations for that ModifyTable were pruned. To enable that,
ExecDoInitialPruning() ensures the first relation is locked if it was
pruned and locking is necessary.
To support this exception to the pruning logic, PlannedStmt now
includes a list of RT indexes identifying the first result relation
of each ModifyTable node in the plan. This allows
ExecDoInitialPruning() to check whether each such relation was
pruned and, if so, lock it if necessary.
Bug: #18830
Reported-by: Robins Tharakan <tharakan@gmail.com>
Diagnozed-by: Tender Wang <tndrwang@gmail.com>
Diagnozed-by: Dean Rasheed <dean.a.rasheed@gmail.com>
Co-authored-by: Dean Rasheed <dean.a.rasheed@gmail.com>
Reviewed-by: Tender Wang <tndrwang@gmail.com>
Reviewed-by: Dean Rasheed <dean.a.rasheed@gmail.com>
Discussion: https://postgr.es/m/18830-1f31ea1dc930d444%40postgresql.org
The default of 128kB is unchanged, but the upper limit is changed from
32 blocks to 128 blocks, unless the operating system's IOV_MAX is too
low. Some other RDBMSes seem to cap their multi-block buffer pool I/O
around this number, and it seems useful to allow experimentation.
The concrete change is to our definition of PG_IOV_MAX, which provides
the maximum for io_combine_limit and io_max_combine_limit. It also
affects a couple of other places that work with arrays of struct iovec
or smaller objects on the stack, so we still don't want to use the
system IOV_MAX directly without a clamp: it is not under our control and
likely to be 1024. 128 seems acceptable for our current usage.
For Windows, we can't use real scatter/gather yet, so we continue to
define our own IOV_MAX value of 16 and emulate preadv()/pwritev() with
loops. Someone would need to research the trade-offs of raising that
number.
NB if trying to see this working: you might temporarily need to hack
BAS_BULKREAD to be bigger, since otherwise the obvious way of "a very
big SELECT" is limited by that for now.
Suggested-by: Tomas Vondra <tomas@vondra.me>
Discussion: https://postgr.es/m/CA%2BhUKG%2B2T9p-%2BzM6Eeou-RAJjTML6eit1qn26f9twznX59qtCA%40mail.gmail.com
The existing io_combine_limit can be changed by users. The new
io_max_combine_limit is fixed at server startup time, and functions as a
silent clamp on the user setting. That in itself is probably quite
useful, but the primary motivation is:
aio_init.c allocates shared memory for all asynchronous IOs including
some per-block data, and we didn't want to waste memory you'd never used
by assuming they could be up to PG_IOV_MAX. This commit already halves
the size of 'AioHandleIov' and 'AioHandleData'. A follow-up commit can
now expand PG_IOV_MAX without affecting that.
Since our GUC system doesn't support dependencies or cross-checks
between GUCs, the user-settable one now assigns a "raw" value to
io_combine_limit_guc, and the lower of io_combine_limit_guc and
io_max_combine_limit is maintained in io_combine_limit.
Reviewed-by: Andres Freund <andres@anarazel.de> (earlier version)
Discussion: https://postgr.es/m/CA%2BhUKG%2B2T9p-%2BzM6Eeou-RAJjTML6eit1qn26f9twznX59qtCA%40mail.gmail.com
Autovacuum launchers perform no WAL IO reads, but pgstat_tracks_io_op()
was tracking them as an allowed combination for the "init" and "normal"
contexts.
This caused the "read", "read_bytes" and "read_time" attributes of
pg_stat_io to show zeros for the autovacuum launcher rather than NULL.
NULL means that a combination of IO object, IO context and IO operation
has no meaning for a backend type. Zero is the same as telling that a
combination is relevant, and that WAL reads are possible in an
autovacuum launcher, but it is not relevant.
Copy-pasto introduced in a051e71e28.
Author: Ranier Vilela <ranier.vf@gmail.com>
Reviewed-by: Nazir Bilal Yavuz <byavuz81@gmail.com>
Discussion: https://postgr.es/m/CAEudQAopEMAPiUqE7BvDV+x2fUPmKmb9RrsaoDR+hhQzLKg4PQ@mail.gmail.com
bbf668d66f lowered the minimum value of maintenance_work_mem to
64kB. However, in parallel vacuum cases, since the initial underlying
DSA size is 256kB, it attempts to perform a cycle of index vacuuming
and table vacuuming with an empty TID store, resulting in an assertion
failure.
This commit ensures that at least one page is processed before index
vacuuming and table vacuuming begins.
Backpatch to 17, where the minimum maintenance_work_mem value was
lowered.
Reviewed-by: David Rowley <dgrowleyml@gmail.com>
Discussion: https://postgr.es/m/CAD21AoCEAmbkkXSKbj4dB+5pJDRL4ZHxrCiLBgES_g_g8mVi1Q@mail.gmail.com
Backpatch-through: 17
