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synchronous_standby_names cannot be reloaded safely by backends, and the
checkpointer is in charge of updating a state in shared memory if the
GUC is enabled in WalSndCtl, to let the backends know if they should
wait or not for a given LSN. This provides a strict control on the
timing of the waiting queues if the GUC is enabled or disabled, then
reloaded. The checkpointer is also in charge of waking up the backends
that could be waiting for a LSN when the GUC is disabled.
This logic had a race condition at startup, where it would be possible
for backends to not wait for a LSN even if synchronous_standby_names is
enabled. This would cause visibility issues with transactions that we
should be waiting for but they were not. The problem lasts until the
checkpointer does its initial update of the shared memory state when it
loads synchronous_standby_names.
In order to take care of this problem, the shared memory state in
WalSndCtl is extended to detect if it has been initialized by the
checkpointer, and not only check if synchronous_standby_names is
defined. In WalSndCtlData, sync_standbys_defined is renamed to
sync_standbys_status, a bits8 able to know about two states:
- If the shared memory state has been initialized. This flag is set by
the checkpointer at startup once, and never removed.
- If synchronous_standby_names is known as defined in the shared memory
state. This is the same as the previous sync_standbys_defined in
WalSndCtl.
This method gives a way for backends to decide what they should do until
the shared memory area is initialized, and they now ultimately fall back
to a check on the GUC value in this case, which is the best thing that
can be done.
Fortunately, SyncRepUpdateSyncStandbysDefined() is called immediately by
the checkpointer when this process starts, so the window is very narrow.
It is possible to enlarge the problematic window by making the
checkpointer wait at the beginning of SyncRepUpdateSyncStandbysDefined()
with a hardcoded sleep for example, and doing so has showed that a 2PC
visibility test is indeed failing. On machines slow enough, this bug
would cause spurious failures.
In 17~, we have looked at the possibility of adding an injection point
to have a reproducible test, but as the problematic window happens at
early startup, we would need to invent a way to make an injection point
optionally persistent across restarts when attached, something that
would be fine for this case as it would involve the checkpointer. This
issue is quite old, and can be reproduced on all the stable branches.
Author: Melnikov Maksim <m.melnikov@postgrespro.ru>
Co-authored-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/163fcbec-900b-4b07-beaa-d2ead8634bec@postgrespro.ru
Backpatch-through: 13
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Data loss can happen when the DDLs like ALTER PUBLICATION ... ADD TABLE ...
or ALTER TYPE ... that don't take a strong lock on table happens
concurrently to DMLs on the tables involved in the DDL. This happens
because logical decoding doesn't distribute invalidations to concurrent
transactions and those transactions use stale cache data to decode the
changes. The problem becomes bigger because we keep using the stale cache
even after those in-progress transactions are finished and skip the
changes required to be sent to the client.
This commit fixes the issue by distributing invalidation messages from
catalog-modifying transactions to all concurrent in-progress transactions.
This allows the necessary rebuild of the catalog cache when decoding new
changes after concurrent DDL.
We observed performance regression primarily during frequent execution of
*publication DDL* statements that modify the published tables. The
regression is minor or nearly nonexistent for DDLs that do not affect the
published tables or occur infrequently, making this a worthwhile cost to
resolve a longstanding data loss issue.
An alternative approach considered was to take a strong lock on each
affected table during publication modification. However, this would only
address issues related to publication DDLs (but not the ALTER TYPE ...)
and require locking every relation in the database for publications
created as FOR ALL TABLES, which is impractical.
The bug exists in all supported branches, but we are backpatching till 14.
The fix for 13 requires somewhat bigger changes than this fix, so the fix
for that branch is still under discussion.
Reported-by: hubert depesz lubaczewski <depesz@depesz.com>
Reported-by: Tomas Vondra <tomas.vondra@enterprisedb.com>
Author: Shlok Kyal <shlok.kyal.oss@gmail.com>
Author: Hayato Kuroda <kuroda.hayato@fujitsu.com>
Reviewed-by: Zhijie Hou <houzj.fnst@fujitsu.com>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Tested-by: Benoit Lobréau <benoit.lobreau@dalibo.com>
Backpatch-through: 14
Discussion: https://postgr.es/m/de52b282-1166-1180-45a2-8d8917ca74c6@enterprisedb.com
Discussion: https://postgr.es/m/CAD21AoAenVqiMjpN-PvGHL1N9DWnHSq673bfgr6phmBUzx=kLQ@mail.gmail.com
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The changes made in commit d2b4b4c2259 contained incorrect comments:
They said that certain forward declarations were necessary to "avoid
including pathnodes.h here", but the file is itself pathnodes.h! So
change the comment to just say it's a forward declaration in one case,
and in the other case we don't need the declaration at all because it
already appeared earlier in the file.
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As of 15.4, macOS has strchrnul(), but access to it is blocked behind
a check for MACOSX_DEPLOYMENT_TARGET >= 15.4. But our does-it-link
configure check finds it, so we try to use it, and fail with the
present default deployment target (namely 15.0). This accounts for
today's buildfarm failures on indri and sifaka.
This is the identical problem that we faced some years ago when Apple
introduced preadv and pwritev in the same way. We solved that in
commit f014b1b9b by using AC_CHECK_DECLS instead of AC_CHECK_FUNCS
to check the functions' availability. So do the same now for
strchrnul(). Interestingly, we already had a workaround for
"the link check doesn't agree with <string.h>" cases with glibc,
which we no longer need since only the header declaration is being
checked.
Testing this revealed that the meson version of this check has never
worked, because it failed to use "-Werror=unguarded-availability-new".
(Apparently nobody's tried to build with meson on macOS versions that
lack preadv/pwritev as standard.) Adjust that while at it. Also,
we had never put support for "-Werror=unguarded-availability-new"
into v13, but we need that now.
Co-authored-by: Tom Lane <tgl@sss.pgh.pa.us>
Co-authored-by: Peter Eisentraut <peter@eisentraut.org>
Discussion: https://postgr.es/m/385134.1743523038@sss.pgh.pa.us
Backpatch-through: 13
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If a domain type has a default, adding a column of that type (without
any explicit DEFAULT clause) failed to install the domain's default
value in existing rows, instead leaving the new column null. This
is unexpected, and it used to work correctly before v11. The cause
is confusion in the atthasmissing mechanism about which default value
to install: we'd only consider installing an explicitly-specified
default, and then we'd decide that no table rewrite is needed.
To fix, take the responsibility for filling attmissingval out of
StoreAttrDefault, and instead put it into ATExecAddColumn's existing
logic that derives the correct value to fill the new column with.
Also, centralize the logic that determines the need for
default-related table rewriting there, instead of spreading it over
four or five places.
In the back branches, we'll leave the attmissingval-filling code
in StoreAttrDefault even though it's now dead, for fear that some
extension may be depending on that functionality to exist there.
A separate HEAD-only patch will clean up the now-useless code.
Reported-by: jian he <jian.universality@gmail.com>
Author: jian he <jian.universality@gmail.com>
Author: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/CACJufxHFssPvkP1we7WMhPD_1kwgbG52o=kQgL+TnVoX5LOyCQ@mail.gmail.com
Backpatch-through: 13
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Due to misunderstanding on my part, commit 235328ee4 did not go far
enough to silence older versions of Valgrind. For those, it was the bit
scan that was problematic, not the subsequent bit-masking operation. To
fix, use the unaligned path for the trailing bytes. Since we don't have
a bit scan here anymore, also remove some comments and endian-specific
coding around that.
Reported-by: Anton A. Melnikov <a.melnikov@postgrespro.ru>
Discussion: https://postgr.es/m/f3aa2d45-3b28-41c5-9499-a1bc30e0f8ec@postgrespro.ru
Backpatch-through: 17
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This commit adds fmtIdEnc() and fmtQualifiedIdEnc(), which allow to specify
the encoding as an explicit argument. Additionally setFmtEncoding() is
provided, which defines the encoding when no explicit encoding is provided, to
avoid breaking all code using fmtId().
All users of fmtId()/fmtQualifiedId() are either converted to the explicit
version or a call to setFmtEncoding() has been added.
This commit does not yet utilize the now well-defined encoding, that will
happen in a subsequent commit.
Reviewed-by: Noah Misch <noah@leadboat.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Backpatch-through: 13
Security: CVE-2025-1094
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There are cases where we cannot / do not want to error out for invalidly
encoded input. In such cases it can be useful to replace e.g. an incomplete
multi-byte characters with bytes that will trigger an error when getting
validated as part of a larger string.
Unfortunately, until now, for some encoding no such sequence existed. For
those encodings this commit removes one previously accepted input combination
- we consider that to be ok, as the chosen bytes are outside of the valid
ranges for the encodings, we just previously failed to detect that.
As we cannot add a new field to pg_wchar_table without breaking ABI, this is
implemented "in-line" in the newly added function.
Author: Noah Misch <noah@leadboat.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Backpatch-through: 13
Security: CVE-2025-1094
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Previously, if a backend that attached to a shared tree attempted to
start iteration, it resulted in a crash. This commit resolves the
issue by ensuring iter_context is created in RT_ATTACH().
This fix applies only to v17, where radixtree.h was introduced. In the
master branch, this issue was separately resolved by 960013f2a1, which
eliminated the iter_context entirely.
Reviewed-by: John Naylor
Discussion: https://postgr.es/m/CAD21AoBB2U47V=F+wQRB1bERov_of5=BOZGaybjaV8FLQyqG3Q@mail.gmail.com
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If a column is omitted in an INSERT, and there's no column default,
the code in preptlist.c generates a NULL Const to be inserted.
Furthermore, if the column is of a domain type, we wrap the Const
in CoerceToDomain, so as to throw a run-time error if the domain
has a NOT NULL constraint. That's fine as far as it goes, but
there are two problems:
1. We're being sloppy about the type/typmod that the Const is
labeled with. It really should have the domain's base type/typmod,
since it's the input to CoerceToDomain not the output. This can
result in coerce_to_domain inserting a useless length-coercion
function (useless because it's being applied to a null). The
coercion would typically get const-folded away later, but it'd
be better not to create it in the first place.
2. We're not applying expression preprocessing (specifically,
eval_const_expressions) to the resulting expression tree.
The planner's primary expression-preprocessing pass already happened,
so that means the length coercion step and CoerceToDomain node miss
preprocessing altogether.
This is at the least inefficient, since it means the length coercion
and CoerceToDomain will actually be executed for each inserted row,
though they could be const-folded away in most cases. Worse, it
seems possible that missing preprocessing for the length coercion
could result in an invalid plan (for example, due to failing to
perform default-function-argument insertion). I'm not aware of
any live bug of that sort with core datatypes, and it might be
unreachable for extension types as well because of restrictions of
CREATE CAST, but I'm not entirely convinced that it's unreachable.
Hence, it seems worth back-patching the fix (although I only went
back to v14, as the patch doesn't apply cleanly at all in v13).
There are several places in the rewriter that are building null
domain constants the same way as preptlist.c. While those are
before the planner and hence don't have any reachable bug, they're
still applying a length coercion that will be const-folded away
later, uselessly wasting cycles. Hence, make a utility routine
that all of these places can call to do it right.
Making this code more careful about the typmod assigned to the
generated NULL constant has visible but cosmetic effects on some
of the plans shown in contrib/postgres_fdw's regression tests.
Discussion: https://postgr.es/m/1865579.1738113656@sss.pgh.pa.us
Backpatch-through: 14
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When running on Windows, canonicalize_path() converts '\' to '/'
to prevent confusing the Windows command processor. It was
doing that in a non-encoding-aware fashion; but in SJIS there
are valid two-byte characters whose second byte matches '\'.
So encoding corruption ensues if such a character is used in
the path.
We can fairly easily fix this if we know which encoding is
in use, but a lot of our utilities don't have much of a clue
about that. After some discussion we decided we'd settle for
fixing this only in psql, and assuming that its value of
client_encoding matches what the user is typing.
It seems hopeless to get the server to deal with the problematic
characters in database path names, so we'll just declare that
case to be unsupported. That means nothing need be done in
the server, nor in utility programs whose only contact with
file path names is for database paths. But psql frequently
deals with client-side file paths, so it'd be good if it
didn't mess those up.
Bug: #18735
Reported-by: Koichi Suzuki <koichi.suzuki@enterprisedb.com>
Author: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Koichi Suzuki <koichi.suzuki@enterprisedb.com>
Discussion: https://postgr.es/m/18735-4acdb3998bb9f2b1@postgresql.org
Backpatch-through: 13
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This reverts commit a365d9e2e8c1ead27203a4431211098292777d3b.
Older versions of Valgrind raise an error, so go back to the bytewise
loop for the final word in the input.
Reported-by: Anton A. Melnikov <a.melnikov@postgrespro.ru>
Discussion: https://postgr.es/m/a3a959f6-14b8-4819-ac04-eaf2aa2e868d@postgrespro.ru
Backpatch-through: 17
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The right mix of DDL and VACUUM could corrupt a catalog page header such
that PageIsVerified() durably fails, requiring a restore from backup.
This affects only catalogs that both have a syscache and have DDL code
that uses syscache tuples to construct updates. One of the test
permutations shows a variant not yet fixed.
This makes !TransactionIdIsValid(TM_FailureData.xmax) possible with
TM_Deleted. I think core and PGXN are indifferent to that.
Per bug #17821 from Alexander Lakhin. Back-patch to v13 (all supported
versions). The test case is v17+, since it uses INJECTION_POINT.
Discussion: https://postgr.es/m/17821-dd8c334263399284@postgresql.org
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Assume twophase.c is the performance-sensitive caller, and preserve its
choice of unlikely() branch hint. Add some retrospective rationale for
that choice. Back-patch to v17, for the next commit to use it.
Reviewed (in earlier versions) by Michael Paquier.
Discussion: https://postgr.es/m/17821-dd8c334263399284@postgresql.org
Discussion: https://postgr.es/m/20250116010051.f3.nmisch@google.com
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The freshly-released 2025a version of tzdata has a refined estimate
for the longitude of Manila, changing their value for LMT in
pre-standardized-timezone days. This changes the output of one of
our test cases. Since we need to be able to run with system tzdata
files that may or may not contain this update, we'd better stop
making that specific test.
I switched it to use Asia/Singapore, which has a roughly similar UTC
offset. That LMT value hasn't changed in tzdb since 2003, so we can
hope that it's well established.
I also noticed that this set of make_timestamptz tests only exercises
zones east of Greenwich, which seems rather sad, and was not the
original intent AFAICS. (We've already changed these tests once
to stabilize their results across tzdata updates, cf 66b737cd9;
it looks like I failed to consider the UTC-offset-sign aspect then.)
To improve that, add a test with Pacific/Honolulu. That LMT offset
is also quite old in tzdb, so we'll cross our fingers that it doesn't
get improved.
Reported-by: Christoph Berg <cb@df7cb.de>
Discussion: https://postgr.es/m/Z46inkznCxesvDEb@msg.df7cb.de
Backpatch-through: 13
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In the name of ABI stability (that is, to avoid a library major
version bump for libpq), libpq still exports a version of pqsignal()
that we no longer want to use ourselves. However, since that has
the same link name as the function exported by src/port/pqsignal.c,
there is a link ordering dependency determining which version will
actually get used by code that uses libpq as well as libpgport.a.
It now emerges that the wrong version has been used by pgbench and
psql since commit 06843df4a rearranged their link commands. This
can result in odd failures in pgbench with the -T switch, since its
SIGALRM handler will now not be marked SA_RESTART. psql may have
some edge-case problems in \watch, too.
Since we don't want to depend on link ordering effects anymore,
let's fix this in the same spirit as b6c7cfac8: use macros to change
the actual link names of the competing functions. We cannot change
legacy-pqsignal.c's exported name of course, so the victim has to be
src/port/pqsignal.c.
In master, rename its exported name to be pqsignal_fe in frontend or
pqsignal_be in backend. (We could perhaps have gotten away with using
the same symbol in both cases, but since the FE and BE versions now
work a little differently, it seems advisable to use different names.)
In back branches, rename to pqsignal_fe in frontend but keep it as
pqsignal in backend. The frontend change could affect third-party
code that is calling pqsignal from libpgport.a or libpgport_shlib.a,
but only if the code is compiled against port.h from a different minor
release than libpgport. Since we don't support using libpgport as a
shared library, it seems unlikely that there will be such a problem.
I left the backend symbol unchanged to avoid an ABI break for
extensions. This means that the link ordering hazard still exists
for any extension that links against libpq. However, none of our own
extensions use both pqsignal() and libpq, and we're not making things
any worse for third-party extensions that do.
Report from Andy Fan, diagnosis by Fujii Masao, patch by me.
Back-patch to all supported branches, as 06843df4a was.
Discussion: https://postgr.es/m/87msfz5qv2.fsf@163.com
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If a new catalog tuple is inserted that belongs to a catcache list
entry, and cache invalidation happens while the list entry is being
built, the list entry might miss the newly inserted tuple.
To fix, change the way we detect concurrent invalidations while a
catcache entry is being built. Keep a stack of entries that are being
built, and apply cache invalidation to those entries in addition to
the real catcache entries. This is similar to the in-progress list in
relcache.c.
Back-patch to all supported versions.
Reviewed-by: Noah Misch
Discussion: https://www.postgresql.org/message-id/2234dc98-06fe-42ed-b5db-ac17384dc880@iki.fi
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The originally submitted code (using bit masking) was correct when the
number of slots was restricted to be a power of two -- but that
limitation was removed during development that led to commit
53c2a97a9266, which made the bank selection code incorrect. This led to
always using a smaller number of banks than available. Change said code
to use integer modulo instead, which works correctly with an arbitrary
number of banks.
It's likely that we could improve on this to avoid runtime use of
integer division. But with this change we're, at least, not wasting
memory on unused banks, and more banks mean less contention, which is
likely to have a much higher performance impact than a single
instruction's latency.
Author: Yura Sokolov <y.sokolov@postgrespro.ru>
Reviewed-by: Andrey Borodin <x4mmm@yandex-team.ru>
Discussion: https://postgr.es/m/9444dc46-ca47-43ed-9058-89c456316306@postgrespro.ru
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Change our ftruncate() macro to use the 64-bit variant of chsize(), and
add a new macro to redirect lseek() to _lseeki64().
Back-patch to all supported releases, in preparation for a bug fix.
Tested-by: Davinder Singh <davinder.singh@enterprisedb.com>
Discussion: https://postgr.es/m/CAKZiRmyM4YnokK6Oenw5JKwAQ3rhP0YTz2T-tiw5dAQjGRXE3Q%40mail.gmail.com
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It's possible that external code is calling smgrtruncate(). Any
external callers might like to consider the recent changes to
RelationTruncate(), but commit 38c579b0 should not have changed the
function prototype in the back-branches, per ABI stability policy.
Restore smgrtruncate()'s traditional argument list in the back-branches,
but make it a wrapper for a new function smgrtruncate2(). The three
callers in core can use smgrtruncate2() directly. In master (18-to-be),
smgrtruncate2() is effectively renamed to smgrtruncate(), so this wart
is cleaned up.
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/CA%2BhUKG%2BThae6x6%2BjmQiuALQBT2Ae1ChjMh1%3DkMvJ8y_SBJZrvA%40mail.gmail.com
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These are also present in procnumber.h
Reported-by: Peter Eisentraut
Discussion: https://www.postgresql.org/message-id/bd04d675-4672-4f87-800a-eb5d470c15fc@eisentraut.org
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Cause parallel workers to not check datallowconn, rolcanlogin, and
ACL_CONNECT privileges. The leader already checked these things
(except for rolcanlogin which might have been checked for a different
role). Re-checking can accomplish little except to induce unexpected
failures in applications that might not even be aware that their query
has been parallelized. We already had the principle that parallel
workers rely on their leader to pass a valid set of authorization
information, so this change just extends that a bit further.
Also, modify the ReservedConnections, datconnlimit and rolconnlimit
logic so that these limits are only enforced against regular backends,
and only regular backends are counted while checking if the limits
were already reached. Previously, background processes that had an
assigned database or role were subject to these limits (with rather
random exclusions for autovac workers and walsenders), and the set of
existing processes that counted against each limit was quite haphazard
as well. The point of these limits, AFAICS, is to ensure the
availability of PGPROC slots for regular backends. Since all other
types of processes have their own separate pools of PGPROC slots, it
makes no sense either to enforce these limits against them or to count
them while enforcing the limit.
While edge-case failures of these sorts have been possible for a
long time, the problem got a good deal worse with commit 5a2fed911
(CVE-2024-10978), which caused parallel workers to make some of these
checks using the leader's current role where before we had used its
AuthenticatedUserId, thus allowing parallel queries to fail after
SET ROLE. The previous behavior was fairly accidental and I have
no desire to return to it.
This patch includes reverting 73c9f91a1, which was an emergency hack
to suppress these same checks in some cases. It wasn't complete,
as shown by a recent bug report from Laurenz Albe. We can also revert
fd4d93d26 and 492217301, which hacked around the same problems in one
regression test.
In passing, remove the special case for autovac workers in
CheckMyDatabase; it seems cleaner to have AutoVacWorkerMain pass
the INIT_PG_OVERRIDE_ALLOW_CONNS flag, now that that does what's
needed.
Like 5a2fed911, back-patch to supported branches (which sadly no
longer includes v12).
Discussion: https://postgr.es/m/1808397.1735156190@sss.pgh.pa.us
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The need for this was missed in commit 93db6cbda, with the result
being that if we launch a slotsync worker it would consume one of
the PGPROCs in the max_connections pool. That could lead to inability
to launch the worker, or to subsequent failures of connection requests
that should have succeeded according to the configured settings.
Rather than create some one-off infrastructure to support this,
let's group the slotsync worker with the existing autovac launcher
in a new category of "special worker" processes. These are kind of
like auxiliary processes, but they cannot use that infrastructure
because they need to be able to run transactions.
For the moment, make these processes share the PGPROC freelist
used for autovac workers (which previously supplied the autovac
launcher too). This is partly to avoid an ABI change in v17,
and partly because it seems silly to have a freelist with
at most two members. This might be worth revisiting if we grow
enough workers in this category.
Tom Lane and Hou Zhijie. Back-patch to v17.
Discussion: https://postgr.es/m/1808397.1735156190@sss.pgh.pa.us
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Commit aac2c9b4fde889d13f859c233c2523345e72d32b mandated such locking
and attempted to fulfill that mandate, but it missed REASSIGN OWNED.
Hence, it remained possible to lose VACUUM's inplace update of
datfrozenxid if a REASSIGN OWNED processed that database at the same
time. This didn't affect the other inplace-updated catalog, pg_class.
For pg_class, REASSIGN OWNED calls ATExecChangeOwner() instead of the
generic AlterObjectOwner_internal(), and ATExecChangeOwner() fulfills
the locking mandate.
Like in GRANT, implement this by following the locking protocol for any
catalog subject to the generic AlterObjectOwner_internal(). It would
suffice to do this for IsInplaceUpdateOid() catalogs only. Back-patch
to v13 (all supported versions).
Kirill Reshke. Reported by Alexander Kukushkin.
Discussion: https://postgr.es/m/CAFh8B=mpKjAy4Cuun-HP-f_vRzh2HSvYFG3rhVfYbfEBUhBAGg@mail.gmail.com
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RelationTruncate() does three things, while holding an
AccessExclusiveLock and preventing checkpoints:
1. Logs the truncation.
2. Drops buffers, even if they're dirty.
3. Truncates some number of files.
Step 2 could previously be canceled if it had to wait for I/O, and step
3 could and still can fail in file APIs. All orderings of these
operations have data corruption hazards if interrupted, so we can't give
up until the whole operation is done. When dirty pages were discarded
but the corresponding blocks were left on disk due to ERROR, old page
versions could come back from disk, reviving deleted data (see
pgsql-bugs #18146 and several like it). When primary and standby were
allowed to disagree on relation size, standbys could panic (see
pgsql-bugs #18426) or revive data unknown to visibility management on
the primary (theorized).
Changes:
* WAL is now unconditionally flushed first
* smgrtruncate() is now called in a critical section, preventing
interrupts and causing PANIC on file API failure
* smgrtruncate() has a new parameter for existing fork sizes,
because it can't call smgrnblocks() itself inside a critical section
The changes apply to RelationTruncate(), smgr_redo() and
pg_truncate_visibility_map(). That last is also brought up to date with
other evolutions of the truncation protocol.
The VACUUM FileTruncate() failure mode had been discussed in older
reports than the ones referenced below, with independent analysis from
many people, but earlier theories on how to fix it were too complicated
to back-patch. The more recently invented cancellation bug was
diagnosed by Alexander Lakhin. Other corruption scenarios were spotted
by me while iterating on this patch and earlier commit 75818b3a.
Back-patch to all supported releases.
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Reported-by: rootcause000@gmail.com
Reported-by: Alexander Lakhin <exclusion@gmail.com>
Discussion: https://postgr.es/m/18146-04e908c662113ad5%40postgresql.org
Discussion: https://postgr.es/m/18426-2d18da6586f152d6%40postgresql.org
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When #include'ing radixtree.h with RT_SHMEM, it could happen to raise
compiler errors due to missing some declarations of types and
functions.
This commit also removes the inclusion of postgres.h since it's
against our usual convention.
Backpatch to v17, where radixtree.h was introduced.
Reviewed-by: Heikki Linnakangas, Álvaro Herrera
Discussion: https://postgr.es/m/CAD21AoCU9YH%2Bb9Rr8YRw7UjmB%3D1zh8GKQkWNiuN9mVhMvkyrRg%40mail.gmail.com
Backpatch-through: 17
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Our parallel-mode code only works when we are executing a query
in full, so ExecutePlan must disable parallel mode when it is
asked to do partial execution. The previous logic for this
involved passing down a flag (variously named execute_once or
run_once) from callers of ExecutorRun or PortalRun. This is
overcomplicated, and unsurprisingly some of the callers didn't
get it right, since it requires keeping state that not all of
them have handy; not to mention that the requirements for it were
undocumented. That led to assertion failures in some corner
cases. The only state we really need for this is the existing
QueryDesc.already_executed flag, so let's just put all the
responsibility in ExecutePlan. (It could have been done in
ExecutorRun too, leading to a slightly shorter patch -- but if
there's ever more than one caller of ExecutePlan, it seems better
to have this logic in the subroutine than the callers.)
This makes those ExecutorRun/PortalRun parameters unnecessary.
In master it seems okay to just remove them, returning the
API for those functions to what it was before parallelism.
Such an API break is clearly not okay in stable branches,
but for them we can just leave the parameters in place after
documenting that they do nothing.
Per report from Yugo Nagata, who also reviewed and tested
this patch. Back-patch to all supported branches.
Discussion: https://postgr.es/m/20241206062549.710dc01cf91224809dd6c0e1@sraoss.co.jp
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Usually an entry in pg_amop or pg_amproc does not need a dependency on
its amoplefttype/amoprighttype/amproclefttype/amprocrighttype types,
because there is an indirect dependency via the argument types of its
referenced operator or procedure, or via the opclass it belongs to.
However, for some support procedures in some index AMs, the argument
types of the support procedure might not mention the column data type
at all. Also, the amop/amproc entry might be treated as "loose" in
the opfamily, in which case it lacks a dependency on any particular
opclass; or it might be a cross-type entry having a reference to a
datatype that is not its opclass' opcintype.
The upshot of all this is that there are cases where a datatype can
be dropped while leaving behind amop/amproc entries that mention it,
because there is no path in pg_depend showing that those entries
depend on that type. Such entries are harmless in normal activity,
because they won't get used, but they cause problems for maintenance
actions such as dropping the operator family. They also cause pg_dump
to produce bogus output. The previous commit put a band-aid on the
DROP OPERATOR FAMILY failure, but a real fix is needed.
To fix, add pg_depend entries showing that a pg_amop/pg_amproc entry
depends on its lefttype/righttype. To avoid bloating pg_depend too
much, skip this if the referenced operator or function has that type
as an input type. (I did not bother with considering the possible
indirect dependency via the opclass' opcintype; at least in the
reported case, that wouldn't help anyway.)
Probably, the reason this has escaped notice for so long is that
add-on datatypes and relevant opclasses/opfamilies are usually
packaged as extensions nowadays, so that there's no way to drop
a type without dropping the referencing opclasses/opfamilies too.
Still, in the absence of pg_depend entries there's nothing that
constrains DROP EXTENSION to drop the opfamily entries before the
datatype, so it seems possible for a DROP failure to occur anyway.
The specific case that was reported doesn't fail in v13, because
v13 prefers to attach the support procedure to the opclass not the
opfamily. But it's surely possible to construct other edge cases
that do fail in v13, so patch that too.
Per report from Yoran Heling. Back-patch to all supported branches.
Discussion: https://postgr.es/m/Z1MVCOh1hprjK5Sf@gmai021
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Most came in during the 17 cycle, so backpatch there. Some
(particularly reorderbuffer.h) are very old, but backpatching doesn't
seem useful.
Like commits c9d297751959, c4f113e8fef9.
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The approach of declaring a function pointer with an empty argument
list and hoping that the compiler will not complain about casting it
to another type no longer works with C23, because foo() is now
equivalent to foo(void).
We don't need to do this here. With a few struct forward declarations
we can supply a correct argument list without having to pull in
another header file.
(This is the only new warning with C23. Together with the previous
fix a67a49648d9, this makes the whole code compile cleanly under C23.)
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/95c6a9bf-d306-43d8-b880-664ef08f2944%40eisentraut.org
Discussion: https://www.postgresql.org/message-id/flat/87o72eo9iu.fsf%40gentoo.org
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If passed a read-write expanded object pointer, the EEOP_NULLIF
code would hand that same pointer to the equality function
and then (unless equality was reported) also return the same
pointer as its value. This is no good, because a function that
receives a read-write expanded object pointer is fully entitled
to scribble on or even delete the object, thus corrupting the
NULLIF output. (This problem is likely unobservable with the
equality functions provided in core Postgres, but it's easy to
demonstrate with one coded in plpgsql.)
To fix, make sure the pointer passed to the equality function
is read-only. We can still return the original read-write
pointer as the NULLIF result, allowing optimization of later
operations.
Per bug #18722 from Alexander Lakhin. This has been wrong
since we invented expanded objects, so back-patch to all
supported branches.
Discussion: https://postgr.es/m/18722-fd9e645448cc78b4@postgresql.org
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Previously we checked "for <stdbool.h> that conforms to C99" using
autoconf's AC_HEADER_STDBOOL macro. We've required C99 since PostgreSQL
12, so the test was redundant, and under C23 it was broken: autoconf
2.69's implementation doesn't understand C23's new empty header (the
macros it's looking for went away, replaced by language keywords).
Later autoconf versions fixed that, but let's just remove the
anachronistic test.
HAVE_STDBOOL_H and HAVE__BOOL will no longer be defined, but they
weren't directly tested in core or likely extensions (except in 11, see
below). PG_USE_STDBOOL (or USE_STDBOOL in 11 and 12) is still defined
when sizeof(bool) is 1, which should be true on all modern systems.
Otherwise we define our own bool type and values of size 1, which would
fail to compile under C23 as revealed by the broken test. (We'll
probably clean that dead code up in master, but here we want a minimal
back-patchable change.)
This came to our attention when GCC 15 recently started using using C23
by default and failed to compile the replacement code, as reported by
Sam James and build farm animal alligator.
Back-patch to all supported releases, and then two older versions that
also know about <stdbool.h>, per the recently-out-of-support policy[1].
12 requires C99 so it's much like the supported releases, but 11 only
assumes C89 so it now uses AC_CHECK_HEADERS instead of the overly picky
AC_HEADER_STDBOOL. (I could find no discussion of which historical
systems had <stdbool.h> but failed the conformance test; if they ever
existed, they surely aren't relevant to that policy's goals.)
[1] https://wiki.postgresql.org/wiki/Committing_checklist#Policies
Reported-by: Sam James <sam@gentoo.org>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org> (master version)
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> (approach)
Discussion: https://www.postgresql.org/message-id/flat/87o72eo9iu.fsf%40gentoo.org
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Updated to specify that it represents the exact time a slot became
inactive, rather than the period of inactivity.
Reported-by: Peter Smith
Author: Bruce Momjian, Nisha Moond
Reviewed-by: Amit Kapila, Peter Smith
Backpatch-through: 17
Discussion: https://postgr.es/m/CAHut+PuvsyA5v8y7rYoY9mkDQzUhwaESM05yCByTMaDoRh30tA@mail.gmail.com
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Commit d39a49c1e4 added new fields to the struct, but missed the "keep
these last" comment on the previous fields. Add placeholder variables
so that the offsets of the fields are the same whether you build with
USE_OPENSSL or not. This is a courtesy to extensions that might peek
at the fields, to make the ABI the same regardless of the options used
to build PostgreSQL.
In reality, I don't expect any extensions to look at the 'raw_buf'
fields. Firstly, they are new in v17, so no one's written such
extensions yet. Secondly, extensions should have no business poking at
those fields anyway. Nevertheless, fix this properly on 'master'. On
v17, we mustn't change the memory layout, so just fix the comments.
Author: Jacob Champion
Discussion: https://www.postgresql.org/message-id/raw/CAOYmi%2BmKVJNzn5_TD_MK%3DhqO64r_w8Gb0FHCLk0oAkW-PJv8jQ@mail.gmail.com
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Commits aac2c9b4f et al. added a bool field to struct ResultRelInfo.
That's no problem in the master branch, but in released branches
care must be taken when modifying publicly-visible structs to avoid
an ABI break for extensions. Frequently we solve that by adding the
new field at the end of the struct, and that's what was done here.
But ResultRelInfo has stricter constraints than just about any other
node type in Postgres. Some executor APIs require extensions to index
into arrays of ResultRelInfo, which means that any change whatever in
sizeof(ResultRelInfo) causes a fatal ABI break.
Fortunately, this is easy to fix, because the new field can be
squeezed into available padding space instead --- indeed, that's where
it was put in master, so this fix also removes a cross-branch coding
variation.
Per report from Pavan Deolasee. Patch v14-v17 only; earlier versions
did not gain the extra field, nor is there any problem in master.
Discussion: https://postgr.es/m/CABOikdNmVBC1LL6pY26dyxAS2f+gLZvTsNt=2XbcyG7WxXVBBQ@mail.gmail.com
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In commit 08c0d6ad6 which introduced "rainbow" arcs in regex NFAs,
I didn't think terribly hard about what to do when creating the color
complement of a rainbow arc. Clearly, the complement cannot match any
characters, and I took the easy way out by just not building any arcs
at all in the complement arc set. That mostly works, but Nikolay
Shaplov found a case where it doesn't: if we decide to delete that
sub-NFA later because it's inside a "{0}" quantifier, delsub()
suffered an assertion failure. That's because delsub() relies on
the target sub-NFA being fully connected. That was always true
before, and the best fix seems to be to restore that property.
Hence, invent a new arc type CANTMATCH that can be generated in
place of an empty color complement, and drop it again later when we
start NFA optimization. (At that point we don't need to do delsub()
any more, and besides there are other cases where NFA optimization can
lead to disconnected subgraphs.)
It appears that this bug has no consequences in a non-assert-enabled
build: there will be some transiently leaked NFA states/arcs, but
they'll get cleaned up eventually. Still, we don't like assertion
failures, so back-patch to v14 where rainbow arcs were introduced.
Per bug #18708 from Nikolay Shaplov.
Discussion: https://postgr.es/m/18708-f94f2599c9d2c005@postgresql.org
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This fixes a set of race conditions with cumulative statistics where a
shared stats entry could be dropped while it should still be valid in
the event when it is reused: an entry may refer to a different object
but requires the same hash key. This can happen with various stats
kinds, like:
- Replication slots that compute internally an index number, for
different slot names.
- Stats kinds that use an OID in the object key, where a wraparound
causes the same key to be used if an OID is used for the same object.
- As of PostgreSQL 18, custom pgstats kinds could also be an issue,
depending on their implementation.
This issue is fixed by introducing a counter called "generation" in the
shared entries via PgStatShared_HashEntry, initialized at 0 when an
entry is created and incremented when the same entry is reused, to avoid
concurrent issues on drop because of other backends still holding a
reference to it. This "generation" is copied to the local copy that a
backend holds when looking at an object, then cross-checked with the
shared entry to make sure that the entry is not dropped even if its
"refcount" justifies that if it has been reused.
This problem could show up when a backend shuts down and needs to
discard any entries it still holds, causing statistics to be removed
when they should not, or even an assertion failure. Another report
involved a failure in a standby after an OID wraparound, where the
startup process would FATAL on a "can only drop stats once", stopping
recovery abruptly. The buildfarm has been sporadically complaining
about the problem, as well, but the window is hard to reach with the
in-core tests.
Note that the issue can be reproduced easily by adding a sleep before
dshash_find() in pgstat_release_entry_ref() to enlarge the problematic
window while repeating test_decoding's isolation test oldest_xmin a
couple of times, for example, as pointed out by Alexander Lakhin.
Reported-by: Alexander Lakhin, Peter Smith
Author: Kyotaro Horiguchi, Michael Paquier
Reviewed-by: Bertrand Drouvot
Discussion: https://postgr.es/m/CAA4eK1KxuMVyAryz_Vk5yq3ejgKYcL6F45Hj9ZnMNBS-g+PuZg@mail.gmail.com
Discussion: https://postgr.es/m/17947-b9554521ad963c9c@postgresql.org
Backpatch-through: 15
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The SQL spec mandates that SET SESSION AUTHORIZATION implies
SET ROLE NONE. We tried to implement that within the lowest-level
functions that manipulate these settings, but that was a bad idea.
In particular, guc.c assumes that it doesn't matter in what order
it applies GUC variable updates, but that was not the case for these
two variables. This problem, compounded by some hackish attempts to
work around it, led to some security-grade issues:
* Rolling back a transaction that had done SET SESSION AUTHORIZATION
would revert to SET ROLE NONE, even if that had not been the previous
state, so that the effective user ID might now be different from what
it had been.
* The same for SET SESSION AUTHORIZATION in a function SET clause.
* If a parallel worker inspected current_setting('role'), it saw
"none" even when it should see something else.
Also, although the parallel worker startup code intended to cope
with the current role's pg_authid row having disappeared, its
implementation of that was incomplete so it would still fail.
Fix by fully separating the miscinit.c functions that assign
session_authorization from those that assign role. To implement the
spec's requirement, teach set_config_option itself to perform "SET
ROLE NONE" when it sets session_authorization. (This is undoubtedly
ugly, but the alternatives seem worse. In particular, there's no way
to do it within assign_session_authorization without incompatible
changes in the API for GUC assign hooks.) Also, improve
ParallelWorkerMain to directly set all the relevant user-ID variables
instead of relying on some of them to get set indirectly. That
allows us to survive not finding the pg_authid row during worker
startup.
In v16 and earlier, this includes back-patching 9987a7bf3 which
fixed a violation of GUC coding rules: SetSessionAuthorization
is not an appropriate place to be throwing errors from.
Security: CVE-2024-10978
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The code in question (pg_preadv() and pg_pwritev()) has been around
for a while, but commit 15c9ac3629 moved it to a header file. If
third-party code that includes this header file is built with
-Wsign-compare on a system without preadv() or pwritev(), warnings
ensue. This commit fixes said warnings by casting the result of
pg_pread()/pg_pwrite() to size_t, which should be safe because we
will have already checked for a negative value.
Author: Wolfgang Walther
Discussion: https://postgr.es/m/16989737-1aa8-48fd-8dfe-b7ada06509ab%40technowledgy.de
Backpatch-through: 17
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Supply a new memory manager for RuntimeDyld, to avoid crashes in
generated code caused by memory placement that can overflow a 32 bit
data type. This is a drop-in replacement for the
llvm::SectionMemoryManager class in the LLVM library, with Michael
Smith's proposed fix from
https://www.github.com/llvm/llvm-project/pull/71968.
We hereby slurp it into our own source tree, after moving into a new
namespace llvm::backport and making some minor adjustments so that it
can be compiled with older LLVM versions as far back as 12. It's harder
to make it work on even older LLVM versions, but it doesn't seem likely
that people are really using them so that is not investigated for now.
The problem could also be addressed by switching to JITLink instead of
RuntimeDyld, and that is the LLVM project's recommended solution as
the latter is about to be deprecated. We'll have to do that soon enough
anyway, and then when the LLVM version support window advances far
enough in a few years we'll be able to delete this code. Unfortunately
that wouldn't be enough for PostgreSQL today: in most relevant versions
of LLVM, JITLink is missing or incomplete.
Several other projects have already back-ported this fix into their fork
of LLVM, which is a vote of confidence despite the lack of commit into
LLVM as of today. We don't have our own copy of LLVM so we can't do
exactly what they've done; instead we have a copy of the whole patched
class so we can pass an instance of it to RuntimeDyld.
The LLVM project hasn't chosen to commit the fix yet, and even if it
did, it wouldn't be back-ported into the releases of LLVM that most of
our users care about, so there is not much point in waiting any longer
for that. If they make further changes and commit it to LLVM 19 or 20,
we'll still need this for older versions, but we may want to
resynchronize our copy and update some comments.
The changes that we've had to make to our copy can be seen by diffing
our SectionMemoryManager.{h,cpp} files against the ones in the tree of
the pull request. Per the LLVM project's license requirements, a copy
is in SectionMemoryManager.LICENSE.
This should fix the spate of crash reports we've been receiving lately
from users on large memory ARM systems.
Back-patch to all supported releases.
Co-authored-by: Thomas Munro <thomas.munro@gmail.com>
Co-authored-by: Anthonin Bonnefoy <anthonin.bonnefoy@datadoghq.com>
Reviewed-by: Anthonin Bonnefoy <anthonin.bonnefoy@datadoghq.com>
Reviewed-by: Daniel Gustafsson <daniel@yesql.se> (license aspects)
Reported-by: Anthonin Bonnefoy <anthonin.bonnefoy@datadoghq.com>
Discussion: https://postgr.es/m/CAO6_Xqr63qj%3DSx7HY6ZiiQ6R_JbX%2B-p6sTPwDYwTWZjUmjsYBg%40mail.gmail.com
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This reverts commit 95c5acb3fc261067ab65ddc0b2dca8e162f09442 (v17) and
counterparts in each other non-master branch. If released, that commit
would have caused a worst-in-years minor release regression, via
undetected LWLock self-deadlock. This commit and its self-deadlock fix
warrant more bake time in the master branch.
Reported by Alexander Lakhin.
Discussion: https://postgr.es/m/10ec0bc3-5933-1189-6bb8-5dec4114558e@gmail.com
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Commit a07e03fd8fa7daf4d1356f7cb501ffe784ea6257 changed inplace updates
to wait for heap_update() commands like GRANT TABLE and GRANT DATABASE.
By keeping the pin during that wait, a sequence of autovacuum workers
and an uncommitted GRANT starved one foreground LockBufferForCleanup()
for six minutes, on buildfarm member sarus. Prevent, at the cost of a
bit of complexity. Back-patch to v12, like the earlier commit. That
commit and heap_inplace_lock() have not yet appeared in any release.
Discussion: https://postgr.es/m/20241026184936.ae.nmisch@google.com
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There are two functions that can be used in event triggers to get more
details about a rewrite happening on a relation. Both had a limited
documentation:
- pg_event_trigger_table_rewrite_reason() and
pg_event_trigger_table_rewrite_oid() were not mentioned in the main
event trigger section in the paragraph dedicated to the event
table_rewrite.
- pg_event_trigger_table_rewrite_reason() returns an integer which is a
bitmap of the reasons why a rewrite happens. There was no explanation
about the meaning of these values, forcing the reader to look at the
code to find out that these are defined in event_trigger.h.
While on it, let's add a comment in event_trigger.h where the
AT_REWRITE_* are defined, telling to update the documentation when
these values are changed.
Backpatch down to 13 as a consequence of 1ad23335f36b, where this area
of the documentation has been heavily reworked.
Author: Greg Sabino Mullane
Discussion: https://postgr.es/m/CAKAnmmL+Z6j-C8dAx1tVrnBmZJu+BSoc68WSg3sR+CVNjBCqbw@mail.gmail.com
Backpatch-through: 13
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The inplace update survives ROLLBACK. The inval didn't, so another
backend's DDL could then update the row without incorporating the
inplace update. In the test this fixes, a mix of CREATE INDEX and ALTER
TABLE resulted in a table with an index, yet relhasindex=f. That is a
source of index corruption. Back-patch to v12 (all supported versions).
The back branch versions don't change WAL, because those branches just
added end-of-recovery SIResetAll(). All branches change the ABI of
extern function PrepareToInvalidateCacheTuple(). No PGXN extension
calls that, and there's no apparent use case in extensions.
Reviewed by Nitin Motiani and (in earlier versions) Andres Freund.
Discussion: https://postgr.es/m/20240523000548.58.nmisch@google.com
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An inplace update's invalidation messages are part of its transaction's
commit record. However, the update survives even if its transaction
aborts or we stop recovery before replaying its transaction commit.
After recovery, a backend that started in recovery could update the row
without incorporating the inplace update. That could result in a table
with an index, yet relhasindex=f. That is a source of index corruption.
This bulk invalidation avoids the functional consequences. A future
change can fix the !RecoveryInProgress() scenario without changing the
WAL format. Back-patch to v17 - v12 (all supported versions). v18 will
instead add invalidations to WAL.
Discussion: https://postgr.es/m/20240618152349.7f.nmisch@google.com
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The decision in b6e1157e7 to ignore raw_expr when evaluating a
JsonValueExpr was incorrect. While its value is not ultimately
used (since formatted_expr's value is), failing to initialize it
can lead to problems, for instance, when the expression tree in
raw_expr contains Aggref nodes, which must be initialized to
ensure the parent Agg node works correctly.
Also, optimize eval_const_expressions_mutator()'s handling of
JsonValueExpr a bit. Currently, when formatted_expr cannot be folded
into a constant, we end up processing it twice -- once directly in
eval_const_expressions_mutator() and again recursively via
ece_generic_processing(). This recursive processing is required to
handle raw_expr. To avoid the redundant processing of formatted_expr,
we now process raw_expr directly in eval_const_expressions_mutator().
Finally, update the comment of JsonValueExpr to describe the roles of
raw_expr and formatted_expr more clearly.
Bug: #18657
Reported-by: Alexander Lakhin <exclusion@gmail.com>
Diagnosed-by: Fabio R. Sluzala <fabio3rs@gmail.com>
Diagnosed-by: Tender Wang <tndrwang@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/18657-1b90ccce2b16bdb8@postgresql.org
Backpatch-through: 16
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C++ requires explicitly casting void pointers to the appropriate
pointer type, which means the foreach_ptr macro cannot be used in
C++ code without this change.
Author: Jelte Fennema-Nio
Reviewed-by: Bruce Momjian
Discussion: https://postgr.es/m/CAGECzQSYG3QfHrc-rOk2KbnB9iJOd7Qu-Xii1s-GTA%3D3JFt49Q%40mail.gmail.com
Backpatch-through: 17
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The previous commit fixed some ways of losing an inplace update. It
remained possible to lose one when a backend working toward a
heap_update() copied a tuple into memory just before inplace update of
that tuple. In catalogs eligible for inplace update, use LOCKTAG_TUPLE
to govern admission to the steps of copying an old tuple, modifying it,
and issuing heap_update(). This includes MERGE commands. To avoid
changing most of the pg_class DDL, don't require LOCKTAG_TUPLE when
holding a relation lock sufficient to exclude inplace updaters.
Back-patch to v12 (all supported versions). In v13 and v12, "UPDATE
pg_class" or "UPDATE pg_database" can still lose an inplace update. The
v14+ UPDATE fix needs commit 86dc90056dfdbd9d1b891718d2e5614e3e432f35,
and it wasn't worth reimplementing that fix without such infrastructure.
Reviewed by Nitin Motiani and (in earlier versions) Heikki Linnakangas.
Discussion: https://postgr.es/m/20231027214946.79.nmisch@google.com
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As previously-added tests demonstrated, heap_inplace_update() could
instead update an unrelated tuple of the same catalog. It could lose
the update. Losing relhasindex=t was a source of index corruption.
Inplace-updating commands like VACUUM will now wait for heap_update()
commands like GRANT TABLE and GRANT DATABASE. That isn't ideal, but a
long-running GRANT already hurts VACUUM progress more just by keeping an
XID running. The VACUUM will behave like a DELETE or UPDATE waiting for
the uncommitted change.
For implementation details, start at the systable_inplace_update_begin()
header comment and README.tuplock. Back-patch to v12 (all supported
versions). In back branches, retain a deprecated heap_inplace_update(),
for extensions.
Reported by Smolkin Grigory. Reviewed by Nitin Motiani, (in earlier
versions) Heikki Linnakangas, and (in earlier versions) Alexander
Lakhin.
Discussion: https://postgr.es/m/CAMp+ueZQz3yDk7qg42hk6-9gxniYbp-=bG2mgqecErqR5gGGOA@mail.gmail.com
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Commits 041b9680 and 6377e12a changed the interface of
scan_analyze_next_block() to take a ReadStream instead of a BlockNumber
and a BufferAccessStrategy, and to return a value to indicate when the
stream has run out of blocks.
This caused integration problems for at least one known extension that
uses specially encoded BlockNumber values that map to different
underlying storage, because acquire_sample_rows() sets up the stream so
that read_stream_next_buffer() reads blocks from the main fork of the
relation's SMgrRelation.
Provide read_stream_next_block(), as a way for such an extension to
access the stream of raw BlockNumbers directly and forward them to its
own ReadBuffer() calls after decoding, as it could in earlier releases.
The new function returns the BlockNumber and BufferAccessStrategy that
were previously passed directly to scan_analyze_next_block().
Alternatively, an extension could wrap the stream of BlockNumbers in
another ReadStream with a callback that performs any decoding required
to arrive at real storage manager BlockNumber values, so that it could
benefit from the I/O combining and concurrency provided by
read_stream.c.
Another class of table access method that does nothing in
scan_analyze_next_block() because it is not block-oriented could use
this function to control the number of block sampling loops. It could
match the previous behavior with "return read_stream_next_block(stream,
&bas) != InvalidBlockNumber".
Ongoing work is expected to provide better ANALYZE support for table
access methods that don't behave like heapam with respect to storage
blocks, but that will be for future releases.
Back-patch to 17.
Reported-by: Mats Kindahl <mats@timescale.com>
Reviewed-by: Mats Kindahl <mats@timescale.com>
Discussion: https://postgr.es/m/CA%2B14425%2BCcm07ocG97Fp%2BFrD9xUXqmBKFvecp0p%2BgV2YYR258Q%40mail.gmail.com
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