Allowing sub-select containing LIMIT/OFFSET in workers can lead to
inconsistent results at the top-level as there is no guarantee that the
row order will be fully deterministic. The fix is to prohibit pushing
LIMIT/OFFSET within sub-selects to workers.
Reported-by: Andrew Fletcher
Bug: 15324
Author: Amit Kapila
Reviewed-by: Dilip Kumar
Backpatch-through: 9.6
Discussion: https://postgr.es/m/153417684333.10284.11356259990921828616@wrigleys.postgresql.org
XLogInsert fails to attach a required FPI to the first record after
full_page_writes is turned on by the last checkpoint. This bug got
introduced in 9.5 due to code rearrangement in commits 2c03216d83 and
2076db2aea. Fix it by ensuring that XLogInsertRecord performs a
recomputation when the given record is generated with FPW as off but
found that the flag has been turned on while actually inserting the
record.
Reported-by: Kyotaro Horiguchi
Author: Kyotaro Horiguchi
Reviewed-by: Amit Kapila
Backpatch-through: 9.5 where this problem was introduced
Discussion: https://postgr.es/m/20180420.151043.74298611.horiguchi.kyotaro@lab.ntt.co.jp
Commit c8ea87e4b introduced a temporary conversion buffer for
substrings extracted during regexp splits. Unfortunately the code that
sized it was failing to ignore the effects of ignored degenerate
regexp matches, so for regexp_split_* calls it could under-size the
buffer in such cases.
Fix, and add some regression test cases (though those will only catch
the bug if run in a multibyte encoding).
Backpatch to 9.3 as the faulty code was.
Thanks to the PostGIS project, Regina Obe and Paul Ramsey for the
report (via IRC) and assistance in analysis. Patch by me.
spgrescan would first reset traversalCxt, and then traverse a
potentially non-empty stack containing pointers to traversalValues
which had been allocated in those contexts, freeing them a second
time. This bug originates in commit ccd6eb49a where traversalValue was
introduced.
Repair by traversing the stack before the context reset; this isn't
ideal, since it means doing retail pfree in a context that's about to
be reset, but the freeing of a stack entry is also done in other
places in the code during the scan so it's not worth trying to
refactor it further. Regression test added.
Backpatch to 9.6 where the problem was introduced.
Per bug #15378; analysis and patch by me, originally from a report on
IRC by user velix; see also PostGIS ticket #4174; review by Alexander
Korotkov.
Discussion: https://postgr.es/m/153663176628.23136.11901365223750051490@wrigleys.postgresql.org
ginRedoRecompress() replays actions over compressed segments of posting list
in-place. However, it might lead to write past pg_upper, because intermediate
state during playing the changes can take more space than both original state
and final state. This commit fixes that by refuse from in-place modification.
Instead page tail is copied once modification is started, and then it's used
as the source of original segments. Backpatch to 9.4 where posting list
compression was introduced.
Reported-by: Sivasubramanian Ramasubramanian
Discussion: https://postgr.es/m/1536091151804.6588%40amazon.com
Author: Alexander Korotkov based on patch from and ideas by Sivasubramanian Ramasubramanian
Review: Sivasubramanian Ramasubramanian
Backpatch-through: 9.4
This patch removes two sources of interference between nominally
independent functions when one SPI-using function calls another,
perhaps without knowing that it does so.
Chapman Flack pointed out that xml.c's query_to_xml_internal() expects
SPI_tuptable and SPI_processed to stay valid across datatype output
function calls; but it's possible that such a call could involve
re-entrant use of SPI. It seems likely that there are similar hazards
elsewhere, if not in the core code then in third-party SPI users.
Previously SPI_finish() reset SPI's API globals to zeroes/nulls, which
would typically make for a crash in such a situation. Restoring them
to the values they had at SPI_connect() seems like a considerably more
useful behavior, and it still meets the design goal of not leaving any
dangling pointers to tuple tables of the function being exited.
Also, cause SPI_connect() to reset these variables to zeroes/nulls after
saving them. This prevents interference in the opposite direction: it's
possible that a SPI-using function that's only ever been tested standalone
contains assumptions that these variables start out as zeroes. That was
the case as long as you were the outermost SPI user, but not so much for
an inner user. Now it's consistent.
Report and fix suggestion by Chapman Flack, actual patch by me.
Back-patch to all supported branches.
Discussion: https://postgr.es/m/9fa25bef-2e4f-1c32-22a4-3ad0723c4a17@anastigmatix.net
It's somewhat surprising that we got away with this before. (Actually,
since nobody tests this routinely AFAIK, it might've been broken for
awhile. But it's definitely broken in the wake of commit f868a8143.)
It seems sufficient to limit the forced recursion to a small number
of levels.
Back-patch to all supported branches, like the preceding patch.
Discussion: https://postgr.es/m/12259.1532117714@sss.pgh.pa.us
LockRelationOid and sibling routines supposed that, if our session already
holds the lock they were asked to acquire, they could skip calling
AcceptInvalidationMessages on the grounds that we must have already read
any remote sinval messages issued against the relation being locked.
This is normally true, but there's a critical special case where it's not:
processing inside AcceptInvalidationMessages might attempt to access system
relations, resulting in a recursive call to acquire a relation lock.
Hence, if the outer call had acquired that same system catalog lock, we'd
fall through, despite the possibility that there's an as-yet-unread sinval
message for that system catalog. This could, for example, result in
failure to access a system catalog or index that had just been processed
by VACUUM FULL. This is the explanation for buildfarm failures we've been
seeing intermittently for the past three months. The bug is far older
than that, but commits a54e1f158 et al added a new recursion case within
AcceptInvalidationMessages that is apparently easier to hit than any
previous case.
To fix this, we must not skip calling AcceptInvalidationMessages until
we have *finished* a call to it since acquiring a relation lock, not
merely acquired the lock. (There's already adequate logic inside
AcceptInvalidationMessages to deal with being called recursively.)
Fortunately, we can implement that at trivial cost, by adding a flag
to LOCALLOCK hashtable entries that tracks whether we know we have
completed such a call.
There is an API hazard added by this patch for external callers of
LockAcquire: if anything is testing for LOCKACQUIRE_ALREADY_HELD,
it might be fooled by the new return code LOCKACQUIRE_ALREADY_CLEAR
into thinking the lock wasn't already held. This should be a fail-soft
condition, though, unless something very bizarre is being done in
response to the test.
Also, I added an additional output argument to LockAcquireExtended,
assuming that that probably isn't called by any outside code given
the very limited usefulness of its additional functionality.
Back-patch to all supported branches.
Discussion: https://postgr.es/m/12259.1532117714@sss.pgh.pa.us
Since the fixes for CVE-2018-1058, we've advised people to schema-qualify
function references in order to fix failures in code that executes under
a minimal search_path setting. However, that's insufficient to make the
single-argument form of unaccent() work, because it looks up the "unaccent"
text search dictionary using the search path.
The most expedient answer seems to be to remove the search_path dependency
by making it look in the same schema that the unaccent() function itself
is declared in. This will definitely work for the normal usage of this
function with the unaccent dictionary provided by the extension.
It's barely possible that there are people who were relying on the
search-path-dependent behavior to select other dictionaries with the same
name; but if there are any such people at all, they can still get that
behavior by writing unaccent('unaccent', ...), or possibly
unaccent('unaccent'::text::regdictionary, ...) if the lookup has to be
postponed to runtime.
Per complaint from Gunnlaugur Thor Briem. Back-patch to all supported
branches.
Discussion: https://postgr.es/m/CAPs+M8LCex6d=DeneofdsoJVijaG59m9V0ggbb3pOH7hZO4+cQ@mail.gmail.com
pg_get_object_address and pg_identify_object_as_address are supposed
to be inverses, but they disagreed as to the names of the arguments
representing the textual form of an object address. Moreover, the
documented argument names didn't agree with reality at all, either
for these functions or pg_identify_object.
In HEAD and v11, I think we can get away with renaming the input
arguments of pg_get_object_address to match the outputs of
pg_identify_object_as_address. In theory that might break queries
using named-argument notation to call pg_get_object_address, but
it seems really unlikely that anybody is doing that, or that they'd
have much trouble adjusting if they were. In older branches, we'll
just live with the lack of consistency.
Aside from fixing the documentation of these functions to match reality,
I couldn't resist the temptation to do some copy-editing.
Per complaint from Jean-Pierre Pelletier. Back-patch to 9.5 where these
functions were introduced. (Before v11, this is a documentation change
only.)
Discussion: https://postgr.es/m/CANGqjDnWH8wsTY_GzDUxbt4i=y-85SJreZin4Hm8uOqv1vzRQA@mail.gmail.com
The previous description was unclear. Also add a third example, change
use of time zone acronyms to more verbose descriptions, and add a
mention that using 'time' with AT TIME ZONE uses the current time zone
rules.
Backpatch-through: 9.3
workers.
Allowing window function calculation in workers leads to inconsistent
results because if the input row ordering is not fully deterministic, the
output of window functions might vary across workers. The fix is to treat
them as parallel-restricted.
In the passing, improve the coding pattern in max_parallel_hazard_walker
so that it has a chain of mutually-exclusive if ... else if ... else if
... else if ... IsA tests.
Reported-by: Marko Tiikkaja
Bug: 15324
Author: Amit Kapila
Reviewed-by: Tom Lane
Backpatch-through: 9.6
Discussion: https://postgr.es/m/CAL9smLAnfPJCDUUG4ckX2iznj53V7VSMsYefzZieN93YxTNOcw@mail.gmail.com
At the beginning of recovery, information from replication slots is
recovered from disk to memory. In order to ensure the durability of the
information, the status file as well as its parent directory are
synced. It happens that the sync on the parent directory was done
directly using the status file path, which is logically incorrect, and
the current code has been doing a sync on the same object twice in a
row.
Reported-by: Konstantin Knizhnik
Diagnosed-by: Konstantin Knizhnik
Author: Michael Paquier
Discussion: https://postgr.es/m/9eb1a6d5-b66f-2640-598d-c5ea46b8f68a@postgrespro.ru
Backpatch-through: 9.4-
This table claimed that JOHAB could be used as a server encoding, which
was true originally but hasn't been true since 8.3. It also lacked
entries for EUC_JIS_2004 and SHIFT_JIS_2004.
JOHAB problem noted by Lars Kanis, the others by me.
Discussion: https://postgr.es/m/c0f514a1-b7a9-b9ea-1c02-c34aead56c06@greiz-reinsdorf.de
There's a project policy against using plain "char buf[BLCKSZ]" local
or static variables as page buffers; preferred style is to palloc or
malloc each buffer to ensure it is MAXALIGN'd. However, that policy's
been ignored in an increasing number of places. We've apparently got
away with it so far, probably because (a) relatively few people use
platforms on which misalignment causes core dumps and/or (b) the
variables chance to be sufficiently aligned anyway. But this is not
something to rely on. Moreover, even if we don't get a core dump,
we might be paying a lot of cycles for misaligned accesses.
To fix, invent new union types PGAlignedBlock and PGAlignedXLogBlock
that the compiler must allocate with sufficient alignment, and use
those in place of plain char arrays.
I used these types even for variables where there's no risk of a
misaligned access, since ensuring proper alignment should make
kernel data transfers faster. I also changed some places where
we had been palloc'ing short-lived buffers, for coding style
uniformity and to save palloc/pfree overhead.
Since this seems to be a live portability hazard (despite the lack
of field reports), back-patch to all supported versions.
Patch by me; thanks to Michael Paquier for review.
Discussion: https://postgr.es/m/1535618100.1286.3.camel@credativ.de
Healthy clients of servers having poor I/O performance, such as
buildfarm members hamster and tern, saw unexpected timeouts. That
disagreed with documentation. This fix adds one gettimeofday() call
whenever ProcessRepliesIfAny() finds no client reply messages.
Back-patch to 9.4; the bug's symptom is rare and mild, and the code all
moved between 9.3 and 9.4.
Discussion: https://postgr.es/m/20180826034600.GA1105084@rfd.leadboat.com
Startup process has improved its calculation of incorrect minimum
consistent point in 8d68ee6, which ensures that all WAL available gets
replayed when doing crash recovery, and has introduced an incorrect
calculation of the minimum recovery point for non-startup processes,
which can cause incorrect page references on a standby when for example
the background writer flushed a couple of pages on-disk but was not
updating the control file to let a subsequent crash recovery replay to
where it should have.
The only case where this has been reported to be a problem is when a
standby needs to calculate the latest removed xid when replaying a btree
deletion record, so one would need connections on a standby that happen
just after recovery has thought it reached a consistent point. Using a
background worker which is started after the consistent point is reached
would be the easiest way to get into problems if it connects to a
database. Having clients which attempt to connect periodically could
also be a problem, but the odds of seeing this problem are much lower.
The fix used is pretty simple, as the idea is to give access to the
minimum recovery point written in the control file to non-startup
processes so as they use a reference, while the startup process still
initializes its own references of the minimum consistent point so as the
original problem with incorrect page references happening post-promotion
with a crash do not show up.
Reported-by: Alexander Kukushkin
Diagnosed-by: Alexander Kukushkin
Author: Michael Paquier
Reviewed-by: Kyotaro Horiguchi, Alexander Kukushkin
Discussion: https://postgr.es/m/153492341830.1368.3936905691758473953@wrigleys.postgresql.org
Backpatch-through: 9.3
contrib/cube has a limit to 100 dimensions for cube datatype. However, it's
not enforced everywhere, and one can actually construct cube with more than
100 dimensions having then trouble with dump/restore. This commit add checks
for dimensions limit in all functions responsible for cube construction.
Backpatch to all supported versions.
Reported-by: Andrew Gierth
Discussion: https://postgr.es/m/87va7uybt4.fsf%40news-spur.riddles.org.uk
Author: Andrey Borodin with small additions by me
Review: Tom Lane
Backpatch-through: 9.3
We're currently maintaining two outputs for cube regression test. But that
appears to be unsuitable, because these outputs are different in out few checks
involving scientific notation. So, split checks involving scientific notation
into separate test, making contrib/cube easier to maintain. Backpatch to all
supported versions in order to make further backpatching easier.
Discussion: https://postgr.es/m/CAPpHfdvJgWjxHsJTtT%2Bo1tz3OR8EFHcLQjhp-d3%2BUcmJLh-fQA%40mail.gmail.com
Author: Alexander Korotkov
Backpatch-through: 9.3
In general, Postgres requires -fno-strict-aliasing with compilers that
implement C99 strict aliasing rules. There's little hope of getting
rid of that overall. But it seems like it would be a good idea if
storage/checksum_impl.h in particular didn't depend on it, because
that header is explicitly intended to be included by external programs.
We don't have a lot of control over the compiler switches that an
external program might use, as shown by Michael Banck's report of
failure in a privately-modified version of pg_verify_checksums.
Hence, switch to using a union in place of willy-nilly pointer casting
inside this file. I think this makes the code a bit more readable
anyway.
checksum_impl.h hasn't changed since it was introduced in 9.3,
so back-patch all the way.
Discussion: https://postgr.es/m/1535618100.1286.3.camel@credativ.de
When a postmaster gets into its phase PM_STARTUP, it would start
background workers using BgWorkerStart_PostmasterStart mode immediately,
which would cause problems for a fast shutdown as the postmaster forgets
to send SIGTERM to already-started background workers. With smart and
immediate shutdowns, this correctly happened, and fast shutdown is the
only mode missing the shot.
Author: Alexander Kukushkin
Reviewed-by: Michael Paquier
Discussion: https://postgr.es/m/CAFh8B=mvnD8+DZUfzpi50DoaDfZRDfd7S=gwj5vU9GYn8UvHkA@mail.gmail.com
Backpatch-through: 9.5
This function had a blacklist of dump object types that it believed
needed exclusive lock ... but we hadn't maintained that, so that it
was missing ROW SECURITY, POLICY, and INDEX ATTACH items, all of
which need (or should be treated as needing) exclusive lock.
Since the same oversight seems likely in future, let's reverse the
sense of the test so that the code has a whitelist of safe object
types; better to wrongly assume a command can't be run in parallel
than the opposite. Currently the only POST_DATA object type that's
safe is CREATE INDEX ... and that list hasn't changed in a long time.
Back-patch to 9.5 where RLS came in.
Discussion: https://postgr.es/m/11450.1535483506@sss.pgh.pa.us
Commit aa09cd242 changed a condition in find_em_expr_for_rel from
being a bms_equal comparison of relids to bms_is_subset, in order to
support order by clauses on foreign joins. But this also allows
through the degenerate case of expressions with no Vars at all (and
hence empty relids), including integer constants which will be parsed
unexpectedly on the remote (viz. "ERROR: ORDER BY position 0 is not in
select list" as in the bug report).
Repair by adding an additional !bms_is_empty test.
Backpatch through to 9.6 where the aforementioned change was made.
Per bug #15352 from Maksym Boguk; analysis and patch by me.
Discussion: https://postgr.es/m/153518420278.1478.14875560810251994661@wrigleys.postgresql.org
regexp_matches, regexp_split_to_table and regexp_split_to_array all
work by compiling a list of match positions as character offsets (NOT
byte positions) in the source string.
Formerly, they then used text_substr to extract the matched text; but
in a multi-byte encoding, that counts the characters in the string,
and the characters needed to reach the starting byte position, on
every call. Accordingly, the performance degraded as the product of
the input string length and the number of match positions, such that
splitting a string of a few hundred kbytes could take many minutes.
Repair by keeping the wide-character copy of the input string
available (only in the case where encoding_max_length is not 1) after
performing the match operation, and extracting substrings from that
instead. This reduces the complexity to being linear in the number of
result bytes, discounting the actual regexp match itself (which is not
affected by this patch).
In passing, remove cleanup using retail pfree() which was obsoleted by
commit ff428cded (Feb 2008) which made cleanup of SRF multi-call
contexts automatic. Also increase (to ~134 million) the maximum number
of matches and provide an error message when it is reached.
Backpatch all the way because this has been wrong forever.
Analysis and patch by me; review by Kaiting Chen.
Discussion: https://postgr.es/m/87pnyn55qh.fsf@news-spur.riddles.org.uk
see also https://postgr.es/m/87lg996g4r.fsf@news-spur.riddles.org.uk
The archive should show a dependency on the item's table, but it failed
to include one. This could cause failures in parallel restore due to
emitting ALTER TABLE ... ENABLE ROW LEVEL SECURITY before restoring
the table's data. In practice the odds of a problem seem low, since
you would typically need to have set FORCE ROW LEVEL SECURITY as well,
and you'd also need a very high --jobs count to have any chance of this
happening. That probably explains the lack of field reports.
Still, it's a bug, so back-patch to 9.5 where RLS was introduced.
Discussion: https://postgr.es/m/19784.1535390902@sss.pgh.pa.us
The previous coding figured it'd be good enough to postpone opening
the first CSV log file until we got a message we needed to write there.
This is unsafe, though, because if the open fails we end up in infinite
recursion trying to report the failure. Instead make the CSV log file
management code look as nearly as possible like the longstanding logic
for the stderr log file. In particular, open it immediately at postmaster
startup (if enabled), or when we get a SIGHUP in which we find that
log_destination has been changed to enable CSV logging.
It seems OK to fail if a postmaster-start-time open attempt fails, as
we've long done for the stderr log file. But we can't die if we fail
to open a CSV log file during SIGHUP, so we're still left with a problem.
In that case, write any output meant for the CSV log file to the stderr
log file. (This will also cover race-condition cases in which backends
send CSV log data before or after we have the CSV log file open.)
This patch also fixes an ancient oversight that, if CSV logging was
turned off during a SIGHUP, we never actually closed the last CSV
log file.
In passing, remember to reset whereToSendOutput = DestNone during syslogger
start, since (unlike all other postmaster children) it's forked before the
postmaster has done that. This made for a platform-dependent difference
in error reporting behavior between the syslogger and other children:
except on Windows, it'd report problems to the original postmaster stderr
as well as the normal error log file(s). It's barely possible that that
was intentional at some point; but it doesn't seem likely to be desirable
in production, and the platform dependency definitely isn't desirable.
Per report from Alexander Kukushkin. It's been like this for a long time,
so back-patch to all supported branches.
Discussion: https://postgr.es/m/CAFh8B==iLUD_gqC-dAENS0V+kVrCeGiKujtKqSQ7++S-caaChw@mail.gmail.com
Mention that "Latest checkpoint location" will not match in pg_upgrade
if the standby server is still running during the upgrade, which is
possible. "Match" text first appeared in PG 9.5.
Reported-by: Paul Bonaud
Discussion: https://postgr.es/m/c7268794-edb4-1772-3bfd-04c54585c24e@trainline.com
Backpatch-through: 9.5
Commits c6b3c939b (which fixed the precedence of >=, <=, <> operators)
and 865f14a2d (which added support for the standard => notation for
named arguments) created a class of lexer tokens which look like
multi-character operators but which have their own token IDs distinct
from Op. However, longest-match rules meant that following any of
these tokens with another operator character, as in (1<>-1), would
cause them to be incorrectly returned as Op.
The error here isn't immediately obvious, because the parser would
usually still find the correct operator via the Op token, but there
were more subtle problems:
1. If immediately followed by a comment or +-, >= <= <> would be given
the old precedence of Op rather than the correct new precedence;
2. If followed by a comment, != would be returned as Op rather than as
NOT_EQUAL, causing it not to be found at all;
3. If followed by a comment or +-, the => token for named arguments
would be lexed as Op, causing the argument to be mis-parsed as a
simple expression, usually causing an error.
Fix by explicitly checking for the operators in the {operator} code
block in addition to all the existing special cases there.
Backpatch to 9.5 where the problem was introduced.
Analysis and patch by me; review by Tom Lane.
Discussion: https://postgr.es/m/87va851ppl.fsf@news-spur.riddles.org.uk
The lexer's handling of operators contained an O(N^3) hazard when
dealing with long strings of + or - characters; it seems hard to
prevent this case from being O(N^2), but the additional N multiplier
was not needed.
Backpatch all the way since this has been there since 7.x, and it
presents at least a mild hazard in that trying to do Bind, PREPARE or
EXPLAIN on a hostile query could take excessive time (without
honouring cancels or timeouts) even if the query was never executed.
While monitoring the code, a couple of issues related to string
translation has showed up:
- Some routines for auto-updatable views return an error string, which
sometimes missed the shot. A comment regarding string translation is
added for each routine to help with future features.
- GSSAPI authentication missed two translations.
- vacuumdb handles non-translated strings.
Reported-by: Kyotaro Horiguchi
Author: Kyotaro Horiguchi
Reviewed-by: Michael Paquier, Tom Lane
Discussion: https://postgr.es/m/20180810.152131.31921918.horiguchi.kyotaro@lab.ntt.co.jp
Backpatch-through: 9.3
Previously, this code blindly followed the common coding pattern of
passing PQserverVersion(AH->connection) as the server-version parameter
of fmtQualifiedId. That works as long as we have a connection; but in
pg_restore with text output, we don't. Instead we got a zero from
PQserverVersion, which fmtQualifiedId interpreted as "server is too old to
have schemas", and so the name went unqualified. That still accidentally
managed to work in many cases, which is probably why this ancient bug went
undetected for so long. It only became obvious in the wake of the changes
to force dump/restore to execute with restricted search_path.
In HEAD/v11, let's deal with this by ripping out fmtQualifiedId's server-
version behavioral dependency, and just making it schema-qualify all the
time. We no longer support pg_dump from servers old enough to need the
ability to omit schema name, let alone restoring to them. (Also, the few
callers outside pg_dump already didn't work with pre-schema servers.)
In older branches, that's not an acceptable solution, so instead just
tweak the DISABLE/ENABLE TRIGGER logic to ensure it will schema-qualify
its output regardless of server version.
Per bug #15338 from Oleg somebody. Back-patch to all supported branches.
Discussion: https://postgr.es/m/153452458706.1316.5328079417086507743@wrigleys.postgresql.org
When executing a SubPlan in an expression, the EState's direction
field was left alone, resulting in an attempt to execute the subplan
backwards if it was encountered during a backwards scan of a cursor.
Also, though much less likely, it was possible to reach the execution
of an InitPlan while in backwards-scan state.
Repair by saving/restoring estate->es_direction and forcing forward
scan mode in the relevant places.
Backpatch all the way, since this has been broken since 8.3 (prior to
commit c7ff7663e, SubPlans had their own EStates rather than sharing
the parent plan's, so there was no confusion over scan direction).
Per bug #15336 reported by Vladimir Baranoff; analysis and patch by
me, review by Tom Lane.
Discussion: https://postgr.es/m/153449812167.1304.1741624125628126322@wrigleys.postgresql.org
The function was forgetting to close the file descriptor, resulting
in failures like this:
ERROR: 53000: exceeded maxAllocatedDescs (492) while trying to open
file "pg_logical/mappings/map-4000-4eb-1_60DE1E08-5376b5-537c6b"
LOCATION: OpenTransientFile, fd.c:2161
Simply close the file at the end, and backpatch to 9.4 (where logical
decoding was introduced). While at it, fix a nearby typo.
Discussion: https://www.postgresql.org/message-id/flat/738a590a-2ce5-9394-2bef-7b1caad89b37%402ndquadrant.com
C99 says that the result should be the number of bytes that would have
been emitted given a large enough buffer, not the number we actually
were able to put in the buffer. It's time to make our substitute
implementation comply with that. Not doing so results in inefficiency
in buffer-enlargement cases, and also poses a portability hazard for
third-party code that might expect C99-compliant snprintf behavior
within Postgres.
In passing, remove useless tests for str == NULL; neither C99 nor
predecessor standards ever allowed that except when count == 0,
so I see no reason to expend cycles on making that a non-crash case
for this implementation. Also, don't waste a byte in pg_vfprintf's
local I/O buffer; this might have performance benefits by allowing
aligned writes during flushbuffer calls.
Back-patch of commit 805889d7d. There was some concern about this
possibly breaking code that assumes pre-C99 behavior, but there is
much more risk (and reality, in our own code) of code that assumes
C99 behavior and hence fails to detect buffer overrun without this.
Discussion: https://postgr.es/m/17245.1534289329@sss.pgh.pa.us
We aren't very strict about keeping FSM up to date on WAL replay,
because per-page freespace values aren't critical in replicas (can't
write to heap in a replica; and if the replica is promoted, the values
would be updated by VACUUM anyway). However, VACUUM since 9.6 can skip
processing pages marked all-visible or all-frozen, and if such pages are
recorded in FSM with wrong values, those values are blindly propagated
to FSM's upper layers by VACUUM's FreeSpaceMapVacuum. (This rationale
assumes that crashes are not very frequent, because those would cause
outdated FSM to occur in the primary.)
Even when the FSM is outdated in standby, things are not too bad
normally, because, most per-page FSM values will be zero (other than
those propagated with the base-backup that created the standby); only
once the remaining free space is less than 0.2*BLCKSZ the per-page value
is maintained by WAL replay of heap ins/upd/del. However, if
wal_log_hints=on causes complete FSM pages to be propagated to a standby
via full-page images, many too-optimistic per-page values can end up
being registered in the standby.
Incorrect per-page values aren't critical in most cases, since an
inserter that is given a page that doesn't actually contain the claimed
free space will update FSM with the correct value, and retry until it
finds a usable page. However, if there are many such updates to do, an
inserter can spend a long time doing them before a usable page is found;
in a heavily trafficked insert-only table with many concurrent inserters
this has been observed to cause several second stalls, causing visible
application malfunction.
To fix this problem, it seems sufficient to have heap_xlog_visible
(replay of setting all-visible and all-frozen VM bits for a heap page)
update the FSM value for the page being processed. This fixes the
per-page counters together with making the page skippable to vacuum, so
when vacuum does FreeSpaceMapVacuum, the values propagated to FSM upper
layers are the correct ones, avoiding the problem.
While at it, apply the same fix to heap_xlog_clean (replay of tuple
removal by HOT pruning and vacuum). This makes any space freed by the
cleaning available earlier than the next vacuum in the promoted replica.
Backpatch to 9.6, where this problem was diagnosed on an insert-only
table with all-frozen pages, which were introduced as a concept in that
release. Theoretically it could apply with all-visible pages to older
branches, but there's been no report of that and it doesn't backpatch
cleanly anyway.
Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://postgr.es/m/20180802172857.5skoexsilnjvgruk@alvherre.pgsql
Fix a small number of places that were testing the result of snprintf()
but doing so incorrectly. The right test for buffer overrun, per C99,
is "result >= bufsize" not "result > bufsize". Some places were also
checking for failure with "result == -1", but the standard only says
that a negative value is delivered on failure.
(Note that this only makes these places correct if snprintf() delivers
C99-compliant results. But at least now these places are consistent
with all the other places where we assume that.)
Also, make psql_start_test() and isolation_start_test() check for
buffer overrun while constructing their shell commands. There seems
like a higher risk of overrun, with more severe consequences, here
than there is for the individual file paths that are made elsewhere
in the same functions, so this seemed like a worthwhile change.
Also fix guc.c's do_serialize() to initialize errno = 0 before
calling vsnprintf. In principle, this should be unnecessary because
vsnprintf should have set errno if it returns a failure indication ...
but the other two places this coding pattern is cribbed from don't
assume that, so let's be consistent.
These errors are all very old, so back-patch as appropriate. I think
that only the shell command overrun cases are even theoretically
reachable in practice, but there's not much point in erroneous error
checks.
Discussion: https://postgr.es/m/17245.1534289329@sss.pgh.pa.us
Commit 244142d32a only tested for the
pg_controldata output for primary servers, but standby servers have
different "Database cluster state" output, so check for that too.
Diagnosed-by: Michael Paquier
Discussion: https://postgr.es/m/20180810164240.GM13638@paquier.xyz
Backpatch-through: 9.3
Currently, we release the asynchronous resources as soon as it is evident
that no more rows will be needed e.g. when a Limit is filled. This can be
problematic especially for custom and foreign scans where we can scan
backward. Fix that by disallowing the shutting down of resources in such
cases.
Reported-by: Robert Haas
Analysed-by: Robert Haas and Amit Kapila
Author: Amit Kapila
Reviewed-by: Robert Haas
Backpatch-through: 9.6 where this code was introduced
Discussion: https://postgr.es/m/86137f17-1dfb-42f9-7421-82fd786b04a1@anayrat.info
exit() is not async-signal safe. Even if the libc implementation is, 3rd
party libraries might have installed unsafe atexit() callbacks. After
receiving SIGQUIT, we really just want to exit as quickly as possible, so
we don't really want to run the atexit() callbacks anyway.
The original report by Jimmy Yih was a self-deadlock in startup_die().
However, this patch doesn't address that scenario; the signal handling
while waiting for the startup packet is more complicated. But at least this
alleviates similar problems in the SIGQUIT handlers, like that reported
by Asim R P later in the same thread.
Backpatch to 9.3 (all supported versions).
Discussion: https://www.postgresql.org/message-id/CAOMx_OAuRUHiAuCg2YgicZLzPVv5d9_H4KrL_OFsFP%3DVPekigA%40mail.gmail.com
CreateUserMapping has a recordDependencyOnCurrentExtension call that's
been there since extensions were introduced (very possibly my fault).
However, there's no support anywhere else for user mappings as members
of extensions, nor are they listed as a possible member object type in
the documentation. Nor does it really seem like a good idea for user
mappings to belong to extensions when roles don't. Hence, remove the
bogus call.
(As we saw in bug #15310, the lack of any pg_dump support for this case
ensures that any such membership record would silently disappear during
pg_upgrade. So there's probably no need for us to do anything else
about cleaning up after this mistake.)
Discussion: https://postgr.es/m/27952.1533667213@sss.pgh.pa.us
Amit Kapila
Peter Eisentraut
Andrew Gierth
Alexander Korotkov
Tom Lane
Bruce Momjian
Michael Paquier
Noah Misch
Thomas Munro
Tomas Vondra
Alvaro Herrera
Heikki Linnakangas