In a similar effort to f736e188c and 110d81728, fixup various usages of
string functions where a more appropriate function is available and more
fit for purpose.
These changes include:
1. Use cstring_to_text_with_len() instead of cstring_to_text() when
working with a StringInfoData and the length can easily be obtained.
2. Use appendStringInfoString() instead of appendStringInfo() when no
formatting is required.
3. Use pstrdup(...) instead of psprintf("%s", ...)
4. Use pstrdup(...) instead of psprintf(...) (with no formatting)
5. Use appendPQExpBufferChar() instead of appendPQExpBufferStr() when the
length of the string being appended is 1.
6. appendStringInfoChar() instead of appendStringInfo() when no formatting
is required and string is 1 char long.
7. Use appendPQExpBufferStr(b, .) instead of appendPQExpBuffer(b, "%s", .)
8. Don't use pstrdup when it's fine to just point to the string constant.
I (David) did find other cases of #8 but opted to use #4 instead as I
wasn't certain enough that applying #8 was ok (e.g in hba.c)
Author: Ranier Vilela, David Rowley
Discussion: https://postgr.es/m/CAApHDvo2j2+RJBGhNtUz6BxabWWh2Jx16wMUMWKUjv70Ver1vg@mail.gmail.com
Since these macros just cast whatever you give them to the designated
output type, and many normal uses also cast the output type further, a
number of incorrect uses go undiscovered. The fixes in this patch
have been discovered by changing these macros to inline functions,
which is the subject of a future patch.
Reviewed-by: Aleksander Alekseev <aleksander@timescale.com>
Discussion: https://www.postgresql.org/message-id/flat/8528fb7e-0aa2-6b54-85fb-0c0886dbd6ed%40enterprisedb.com
XLogPageRead() can retry internally after a pread() system call has
succeeded, in the case of short reads, and page validation failures
while in standby mode (see commit 0668719801). Due to an oversight in
commit 3f1ce973, these cases could leave stale data in the internal
cache of xlogreader.c without marking it invalid. The main defense
against stale cached data on failure to read a page was in the error
handling path of the calling function ReadPageInternal(), but that
wasn't quite enough for errors handled internally by XLogPageRead()'s
retry loop if we then exited with XLREAD_WOULDBLOCK.
1. ReadPageInternal() now marks the cache invalid before calling the
page_read callback, by setting state->readLen to 0. It'll be set to
a non-zero value only after a successful read. It'll stay valid as
long as the caller requests data in the cached range.
2. XLogPageRead() no long performs internal retries while reading
ahead. While such retries should work, the general philosophy is
that we should give up prefetching if anything unusual happens so we
can handle it when recovery catches up, to reduce the complexity of
the system. Let's do that here too.
3. While here, a new function XLogReaderResetError() improves the
separation between xlogrecovery.c and xlogreader.c, where the former
previously clobbered the latter's internal error buffer directly.
The new function makes this more explicit, and also clears a related
flag, without which a standby would needlessly retry in the outer
function.
Thanks to Noah Misch for tracking down the conditions required for a
rare build farm failure in src/bin/pg_ctl/t/003_promote.pl, and
providing a reproducer.
Back-patch to 15.
Reported-by: Noah Misch <noah@leadboat.com>
Discussion: https://postgr.es/m/20220807003627.GA4168930%40rfd.leadboat.com
Several backend-side loops scanning one or more directories with
ReadDir() (WAL segment recycle/removal in xlog.c, backend-side directory
copy, temporary file removal, configuration file parsing, some logical
decoding logic and some pgtz stuff) already know the type of the entry
being scanned thanks to the dirent structure associated to the entry, on
platforms where we know about DT_REG, DT_DIR and DT_LNK to make the
difference between a regular file, a directory and a symbolic link.
Relying on the direct structure of an entry saves a few system calls to
stat() and lstat() in the loops updated here, shaving some code while on
it. The logic of the code remains the same, calling stat() or lstat()
depending on if it is necessary to look through symlinks.
Authors: Nathan Bossart, Bharath Rupireddy
Reviewed-by: Andres Freund, Thomas Munro, Michael Paquier
Discussion: https://postgr.es/m/CALj2ACV8n-J-f=yiLUOx2=HrQGPSOZM3nWzyQQvLPcccPXxEdg@mail.gmail.com
Before now, the cutoffs that VACUUM used to determine which XIDs/MXIDs
to freeze were determined at the start of each VACUUM by taking related
cutoffs that represent which XIDs/MXIDs VACUUM should treat as still
running, and subtracting an XID/MXID age based value controlled by GUCs
like vacuum_freeze_min_age. The FreezeLimit cutoff (XID freeze cutoff)
was derived by subtracting an XID age value from OldestXmin, while the
MultiXactCutoff cutoff (MXID freeze cutoff) was derived by subtracting
an MXID age value from OldestMxact. This approach didn't match the
approach used nearby to determine whether this VACUUM operation should
be an aggressive VACUUM or not.
VACUUM now uses the standard approach instead: it subtracts the same
age-based values from next XID/next MXID (rather than subtracting from
OldestXmin/OldestMxact). This approach is simpler and more uniform.
Most of the time it will have only a negligible impact on how and when
VACUUM freezes. It will occasionally make VACUUM more robust in the
event of problems caused by long running transaction. These are cases
where OldestXmin and OldestMxact are held back by so much that they
attain an age that is a significant fraction of the value of age-based
settings like vacuum_freeze_min_age.
There is no principled reason why freezing should be affected in any way
by the presence of a long-running transaction -- at least not before the
point that the OldestXmin and OldestMxact limits used by each VACUUM
operation attain an age that makes it unsafe to freeze some of the
XIDs/MXIDs whose age exceeds the value of the relevant age-based
settings. The new approach should at least make freezing degrade more
gracefully than before, even in the most extreme cases.
Author: Peter Geoghegan <pg@bowt.ie>
Reviewed-By: Nathan Bossart <nathandbossart@gmail.com>
Reviewed-By: Matthias van de Meent <boekewurm+postgres@gmail.com>
Discussion: https://postgr.es/m/CAH2-WzkOv5CEeyOO=c91XnT5WBR_0gii0Wn5UbZhJ=4TTykDYg@mail.gmail.com
More than twenty years ago (79fcde48b), we hacked the postmaster
to avoid a core-dump on systems that didn't support fflush(NULL).
We've mostly, though not completely, hewed to that rule ever since.
But such systems are surely gone in the wild, so in the spirit of
cleaning out no-longer-needed portability hacks let's get rid of
multiple per-file fflush() calls in favor of using fflush(NULL).
Also, we were fairly inconsistent about whether to fflush() before
popen() and system() calls. While we've received no bug reports
about that, it seems likely that at least some of these call sites
are at risk of odd behavior, such as error messages appearing in
an unexpected order. Rather than expend a lot of brain cells
figuring out which places are at hazard, let's just establish a
uniform coding rule that we should fflush(NULL) before these calls.
A no-op fflush() is surely of trivial cost compared to launching
a sub-process via a shell; while if it's not a no-op then we likely
need it.
Discussion: https://postgr.es/m/2923412.1661722825@sss.pgh.pa.us
When a PostgreSQL instance performing archive recovery but not using
standby mode is promoted, and the last WAL segment that it attempted
to read ended in a partial record, the previous code would create
invalid WAL on the new timeline. The WAL from the previously timeline
would be copied to the new timeline up until the end of the last valid
record, but instead of beginning to write WAL at immediately
afterwards, the promoted server would write an overwrite contrecord at
the beginning of the next segment. The end of the previous segment
would be left as all-zeroes, resulting in failures if anything tried
to read WAL from that file.
The root of the issue is that ReadRecord() decides whether to set
abortedRecPtr and missingContrecPtr based on the value of StandbyMode,
but ReadRecord() switches to a new timeline based on the value of
ArchiveRecoveryRequested. We shouldn't try to write an overwrite
contrecord if we're switching to a new timeline, so change the test in
ReadRecod() to check ArchiveRecoveryRequested instead.
Code fix by Dilip Kumar. Comments by me incorporating suggested
language from Álvaro Herrera. Further review from Kyotaro Horiguchi
and Sami Imseih.
Discussion: http://postgr.es/m/CAFiTN-t7umki=PK8dT1tcPV=mOUe2vNhHML6b3T7W7qqvvajjg@mail.gmail.com
Discussion: http://postgr.es/m/FB0DEA0B-E14E-43A0-811F-C1AE93D00FF3%40amazon.com
In a similar effort to f01592f91, here we're targetting fixing the
warnings where we've deemed the shadowing variable to serve a close enough
purpose to the shadowed variable just to reuse the shadowed version and
not declare the shadowing variable at all.
By my count, this takes the warning count from 106 down to 71.
Author: Justin Pryzby
Discussion: https://postgr.es/m/20220825020839.GT2342@telsasoft.com
These should have been included in 421892a19 as these shadowed variable
warnings can also be fixed by adjusting the scope of the shadowed variable
to put the declaration for it in an inner scope.
This is part of the same effort as f01592f91.
By my count, this takes the warning count from 114 down to 106.
Author: David Rowley and Justin Pryzby
Discussion: https://postgr.es/m/CAApHDvrwLGBP%2BYw9vriayyf%3DXR4uPWP5jr6cQhP9au_kaDUhbA%40mail.gmail.com
This commit moves authn_id into a new global structure called
ClientConnectionInfo (mapping to a MyClientConnectionInfo for each
backend) which is intended to hold all the client information that
should be shared between the backend and any of its parallel workers,
access for extensions and triggers being the primary use case. There is
no need to push all the data of Port to the workers, and authn_id is
quite a generic concept so using a separate structure provides the best
balance (the name of the structure has been suggested by Robert Haas).
While on it, and per discussion as this would be useful for a potential
SYSTEM_USER that can be accessed through parallel workers, a second
field is added for the authentication method, copied directly from
Port.
ClientConnectionInfo is serialized and restored using a new parallel
key and a structure tracks the length of the authn_id, making the
addition of more fields straight-forward.
Author: Jacob Champion
Reviewed-by: Bertrand Drouvot, Stephen Frost, Robert Haas, Tom Lane,
Michael Paquier, Julien Rouhaud
Discussion: https://postgr.es/m/793d990837ae5c06a558d58d62de9378ab525d83.camel@vmware.com
In a similar effort to f01592f91, here we're targetting fixing the
warnings that -Wshadow=compatible-local produces that we can fix by moving
a variable to an inner scope to stop that variable from being shadowed by
another variable declared somewhere later in the function.
All of the warnings being fixed here are changing the scope of variables
which are being used as an iterator for a "for" loop. In each instance,
the fix happens to be changing the for loop to use the C99 type
initialization. Much of this code likely pre-dates our use of C99.
Reducing the scope of the outer scoped variable seems like the safest way
to fix these. Renaming seems more likely to risk patches using the wrong
variable. Reducing the scope is more likely to result in a compilation
failure after applying some future patch rather than introducing bugs with
it.
By my count, this takes the warning count from 129 down to 114.
Author: Justin Pryzby
Discussion: https://postgr.es/m/CAApHDvrwLGBP%2BYw9vriayyf%3DXR4uPWP5jr6cQhP9au_kaDUhbA%40mail.gmail.com
As written, if you use XLogBeginRead() to position an xlogreader at
the beginning of a WAL page and then try to read WAL, this assertion
will fail. However, the header comment for XLogBeginRead() claims
that positioning an xlogreader at the beginning of a page is valid,
and the code here is perfectly able to cope with it. It's only the
assertion that causes trouble. So relax it.
This is formally a bug in all supported branches, but as it doesn't
seem to have any consequences for current uses of the xlogreader
facility, no back-patch, at least for now.
Dilip Kumar and Robert Haas
Discussion: http://postgr.es/m/CA+TgmoaJSs2_7WHW2GzFYe9+zfPtxBKvT3GW47+x=ptUE=cULw@mail.gmail.com
The assert, introduced by 9f1cf97bb5, is intended to check if the prefix
is terminated by a \0 byte, but it has two flaws. Firstly, prefix_size
includes the \0 byte, so prefix[prefix_size] points to the byte after
the null byte. Secondly, the check ensures the byte is not equal \0,
while it should be checking the opposite.
Backpatch-through: 14
Discussion: https://postgr.es/m/b99b6101-2f14-3796-3dfa-4a6cd7d4326d@enterprisedb.com
nbtree deduplication passes add tuples from the original/target page to
a temp page, merging as necessary. The temp page is copied back to the
target permanent page in the critical section. This is similar to the
approach taken by nbtree page splits.
Adjust comments that referred to updating the original page in-place as
tuples were merged. These were left over from earlier versions of the
deduplication patch that didn't yet use a temp page.
pread() and pwrite() are in SUSv2, and all targeted Unix systems have
them.
Previously, we defined pg_pread and pg_pwrite to emulate these function
with lseek() on old Unixen. The names with a pg_ prefix were a reminder
of a portability hazard: they might change the current file position.
That hazard is gone, so we can drop the prefixes.
Since the remaining replacement code is Windows-only, move it into
src/port/win32p{read,write}.c, and move the declarations into
src/include/port/win32_port.h.
No need for vestigial HAVE_PREAD, HAVE_PWRITE macros as they were only
used for declarations in port.h which have now moved into win32_port.h.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Greg Stark <stark@mit.edu>
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CA+hUKGJ3LHeP9w5Fgzdr4G8AnEtJ=z=p6hGDEm4qYGEUX5B6fQ@mail.gmail.com
symlink() and readlink() are in SUSv2 and all targeted Unix systems have
them. We have partial emulation on Windows. Code that raised runtime
errors on systems without it has been dead for years, so we can remove
that and also references to such systems in the documentation.
Define HAVE_READLINK and HAVE_SYMLINK macros on Unix. Our Windows
replacement functions based on junction points can't be used for
relative paths or for non-directories, so the macros can be used to
check for full symlink support. The places that deal with tablespaces
can just use symlink functions without checking the macros. (If they
did check the macros, they'd need to provide an #else branch with a
runtime or compile time error, and it'd be dead code.)
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CA+hUKGJ3LHeP9w5Fgzdr4G8AnEtJ=z=p6hGDEm4qYGEUX5B6fQ@mail.gmail.com
The use of "we" when referring to the active backend might be
misunderstood, so rephrase to make it clearer who is performing
the actions discussed in the comment.
Author: Junwang Zhao <zhjwpku@gmail.com>
Reviewed-by: Erikjan Rijkers <er@xs4all.nl>
Reviewed-by: Robert Treat <rob@xzilla.net>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/CAEG8a3LRSMqkvjiURiJoSi4aGWORpiXUmUfQQK5PaD6WfPzu3w@mail.gmail.com
In the initial data sort, if the bucket numbers are the same then
next sort on the hash value. Because index pages are kept in
hash value order, this gains a little speed by allowing the
eventual tuple insertions to be done sequentially, avoiding repeated
data movement within PageAddItem. This seems to be good for overall
speedup of 5%-9%, depending on the incoming data.
Simon Riggs, reviewed by Amit Kapila
Discussion: https://postgr.es/m/CANbhV-FG-1ZNMBuwhUF7AxxJz3u5137dYL-o6hchK1V_dMw86g@mail.gmail.com
Crash recovery on standby may encounter missing directories
when replaying database-creation WAL records. Prior to this
patch, the standby would fail to recover in such a case;
however, the directories could be legitimately missing.
Consider the following sequence of commands:
CREATE DATABASE
DROP DATABASE
DROP TABLESPACE
If, after replaying the last WAL record and removing the
tablespace directory, the standby crashes and has to replay the
create database record again, crash recovery must be able to continue.
A fix for this problem was already attempted in 49d9cfc68b, but it
was reverted because of design issues. This new version is based
on Robert Haas' proposal: any missing tablespaces are created
during recovery before reaching consistency. Tablespaces
are created as real directories, and should be deleted
by later replay. CheckRecoveryConsistency ensures
they have disappeared.
The problems detected by this new code are reported as PANIC,
except when allow_in_place_tablespaces is set to ON, in which
case they are WARNING. Apart from making tests possible, this
gives users an escape hatch in case things don't go as planned.
Author: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Author: Asim R Praveen <apraveen@pivotal.io>
Author: Paul Guo <paulguo@gmail.com>
Reviewed-by: Anastasia Lubennikova <lubennikovaav@gmail.com> (older versions)
Reviewed-by: Fujii Masao <masao.fujii@oss.nttdata.com> (older versions)
Reviewed-by: Michaël Paquier <michael@paquier.xyz>
Diagnosed-by: Paul Guo <paulguo@gmail.com>
Discussion: https://postgr.es/m/CAEET0ZGx9AvioViLf7nbR_8tH9-=27DN5xWJ2P9-ROH16e4JUA@mail.gmail.com
XLogRecordBlockHeader, the header holding the information for the data
related to a block, tracks the length of the data appended to the WAL
record with data_length (uint16). This limitation in size was not
enforced by the public routine in charge of registering the data
assembled later to form the WAL record inserted, XLogRegisterBufData().
Incorrectly used, it could lead to the generation of records with some
of its data overflowed. This commit adds some safeguards to prevent
that for the block data, complaining immediately if attempting to add to
a record block information with a size larger than UINT16_MAX, which is
the limit implied by the internal logic.
Note that this also adjusts XLogRegisterData() and XLogRegisterBufData()
so as the length of the WAL record data given by the caller is unsigned,
matching with what gets stored in XLogRecData->len.
Extracted from a larger patch by the same author. The original patch
includes more protections when assembling a record in full that will be
looked at separately later.
Author: Matthias van de Meent
Reviewed-by: Andres Freund, Heikki Linnakangas, Michael Paquier, David
Zhang
Discussion: https://postgr.es/m/CAEze2WgGiw+LZt+vHf8tWqB_6VxeLsMeoAuod0N=ij1q17n5pw@mail.gmail.com
We have a few commands that "can't run in a transaction block",
meaning that if they complete their processing but then we fail
to COMMIT, we'll be left with inconsistent on-disk state.
However, the existing defenses for this are only watertight for
simple query protocol. In extended protocol, we didn't commit
until receiving a Sync message. Since the client is allowed to
issue another command instead of Sync, we're in trouble if that
command fails or is an explicit ROLLBACK. In any case, sitting
in an inconsistent state while waiting for a client message
that might not come seems pretty risky.
This case wasn't reachable via libpq before we introduced pipeline
mode, but it's always been an intended aspect of extended query
protocol, and likely there are other clients that could reach it
before.
To fix, set a flag in PreventInTransactionBlock that tells
exec_execute_message to force an immediate commit. This seems
to be the approach that does least damage to existing working
cases while still preventing the undesirable outcomes.
While here, add some documentation to protocol.sgml that explicitly
says how to use pipelining. That's latent in the existing docs if
you know what to look for, but it's better to spell it out; and it
provides a place to document this new behavior.
Per bug #17434 from Yugo Nagata. It's been wrong for ages,
so back-patch to all supported branches.
Discussion: https://postgr.es/m/17434-d9f7a064ce2a88a3@postgresql.org
This commit removes two arguments "report" and "whichChkpt"
in ReadCheckpointRecord().
"report" is obviously useless because it's always true, i.e., there are
two callers of the function and they always specify true as "report".
Commit 1d919de5eb removed the only call with "report" = false.
"whichChkpt" indicated where the specified checkpoint location
came from, pg_control or backup_label. This information was used
to report different error messages depending on where the invalid
checkpoint record came from, when it was found.
But ReadCheckpointRecord() doesn't need to do that because
its callers already do that and users can still identify where
the invalid checkpoint record came from, by reading such log messages.
Also when "whichChkpt" was 0, the word "primary checkpoint" was used
in the log message and could confuse users because the concept of
primary and secondary checkpoints was already removed before.
These are why this commit removes "whichChkpt" argument.
Author: Fujii Masao
Reviewed-by: Bharath Rupireddy, Kyotaro Horiguchi
Discussion: https://postgr.es/m/fa2e12eb-81c3-0717-0272-755f8a81c8f2@oss.nttdata.com
Commit c6f2f016 added an explicit check for a Windows "junction point".
That turned out to be needed only because get_dirent_type() was busted
on Windows. It's been fixed by commit 9d3444dc, so remove it.
Add a TAP-test to demonstrate that in-place tablespaces are copied by
pg_basebackup. This exercises the codepath that would fail before
c6f2f016 on Windows, and shows that it still doesn't fail now that we're
using get_dirent_type() on both Windows and Unix.
Back-patch to 15, where in-place tablespaces arrived and caused this
problem (ie directories where previously only symlinks were expected).
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/CA%2BhUKGLzLK4PUPx0_AwXEWXOYAejU%3D7XpxnYE55Y%2Be7hB2N3FA%40mail.gmail.com
O_FSYNC was a pre-POSIX way of spelling O_SYNC, supported since commit
9d645fd84c for non-conforming operating systems of the time. It's not
needed on any modern system. We can just use standard O_SYNC directly
if it exists (= all targeted systems except Windows), and get rid of our
OPEN_SYNC_FLAG macro.
Similarly for standard O_DSYNC, we can just use that directly if it
exists (= all targeted systems except DragonFlyBSD), and get rid of our
OPEN_DATASYNC_FLAG macro.
We still avoid choosing open_datasync as a default value for
wal_sync_method if O_DSYNC has the same value as O_SYNC (= only
OpenBSD), so there is no change in default behavior.
Discussion: https://postgr.es/m/CA%2BhUKGJE7y92NY7FG2ftUbZUaqohBU65_Ys_7xF5mUHo4wirTQ%40mail.gmail.com
Commit 4f658dc8 provided the traditional BSD fls() function in
src/port/fls.c so it could be used in several places. Later we added a
bunch of similar facilities in pg_bitutils.h, based on compiler
builtins that map to hardware instructions. It's a bit confusing to
have both 1-based and 0-based variants of this operation in use in
different parts of the tree, and neither is blessed by a standard.
Let's drop fls.c and the configure probe, and reuse the newer code.
Reviewed-by: David Rowley <dgrowleyml@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/CA%2BhUKG%2B7dSX1XF8yFGmYk-%3D48dbjH2kmzZj16XvhbrWP-9BzRg%40mail.gmail.com
When a non-exclusive backup is canceled, do_pg_abort_backup() is called
and resets some variables set by pg_backup_start (pg_start_backup in v14
or before). But previously it forgot to reset the session state indicating
whether a non-exclusive backup is in progress or not in this session.
This issue could cause an assertion failure when the session running
BASE_BACKUP is terminated after it executed pg_backup_start and
pg_backup_stop (pg_stop_backup in v14 or before). Also it could cause
a segmentation fault when pg_backup_stop is called after BASE_BACKUP
in the same session is canceled.
This commit fixes the issue by making do_pg_abort_backup reset
that session state.
Back-patch to all supported branches.
Author: Fujii Masao
Reviewed-by: Kyotaro Horiguchi, Masahiko Sawada, Michael Paquier, Robert Haas
Discussion: https://postgr.es/m/3374718f-9fbf-a950-6d66-d973e027f44c@oss.nttdata.com
This replaces all MemSet() calls with struct initialization where that
is easily and obviously possible. (For example, some cases have to
worry about padding bits, so I left those.)
(The same could be done with appropriate memset() calls, but this
patch is part of an effort to phase out MemSet(), so it doesn't touch
memset() calls.)
Reviewed-by: Ranier Vilela <ranier.vf@gmail.com>
Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://www.postgresql.org/message-id/9847b13c-b785-f4e2-75c3-12ec77a3b05c@enterprisedb.com
It is useful for debugging purposes to report the checkpoint LSN and
REDO LSN in log_checkpoints message. It can give more context while
analyzing checkpoint-related issues. pg_controldata reports the last
checkpoint LSN and REDO LSN, but having this information alongside
the log message helps analyze issues that happened previously,
connect the dots and identify the root cause.
Author: Bharath Rupireddy, Kyotaro Horiguchi
Reviewed-by: Michael Paquier, Julien Rouhaud, Nathan Bossart, Fujii Masao, Greg Stark
Discussion: https://postgr.es/m/CALj2ACWt6kqriAHrO+AJj+OmP=suwbktHT5JoYAn-nqZe2gd2g@mail.gmail.com
40af10b57 changed things so we make use of a generation memory context for
storing tuples to be sorted by tuplesort.c. That change does not play
nicely with the changes made in 9f03ca915 (back in 2014). That commit
changed things so that index_form_tuple() is called while switched into
the tuplestore's tuplecontext. In order to fetch the tuple from the index,
index_form_tuple() must do various memory allocations which are unrelated
to the storage of the final returned tuple. Although all of these
allocations are pfree'd, the fact that we now use a generation context
means that the memory for these pfree'd allocations won't be used again by
any other allocation due to generation.c's lack of freelists. This could
result in sorts used for building indexes exceeding maintenance_work_mem
by a very large amount.
Here we fix it so we no longer allocate anything apart from the tuple
itself into the generation context by adding a new version of
index_form_tuple named index_form_tuple_context, which can be called to
specify the MemoryContext to allocate the tuple into.
Discussion: https://postgr.es/m/CAApHDvrHQkiFRHiGiAS-LMOvJN-eK-s762=tVzBz8ZqUea-a_A@mail.gmail.com
Backpatch-through: 15, where 40af10b57 was added.
We have been using the term RelFileNode to refer to either (1) the
integer that is used to name the sequence of files for a certain relation
within the directory set aside for that tablespace/database combination;
or (2) that value plus the OIDs of the tablespace and database; or
occasionally (3) the whole series of files created for a relation
based on those values. Using the same name for more than one thing is
confusing.
Replace RelFileNode with RelFileNumber when we're talking about just the
single number, i.e. (1) from above, and with RelFileLocator when we're
talking about all the things that are needed to locate a relation's files
on disk, i.e. (2) from above. In the places where we refer to (3) as
a relfilenode, instead refer to "relation storage".
Since there is a ton of SQL code in the world that knows about
pg_class.relfilenode, don't change the name of that column, or of other
SQL-facing things that derive their name from it.
On the other hand, do adjust closely-related internal terminology. For
example, the structure member names dbNode and spcNode appear to be
derived from the fact that the structure itself was called RelFileNode,
so change those to dbOid and spcOid. Likewise, various variables with
names like rnode and relnode get renamed appropriately, according to
how they're being used in context.
Hopefully, this is clearer than before. It is also preparation for
future patches that intend to widen the relfilenumber fields from its
current width of 32 bits. Variables that store a relfilenumber are now
declared as type RelFileNumber rather than type Oid; right now, these
are the same, but that can now more easily be changed.
Dilip Kumar, per an idea from me. Reviewed also by Andres Freund.
I fixed some whitespace issues, changed a couple of words in a
comment, and made one other minor correction.
Discussion: http://postgr.es/m/CA+TgmoamOtXbVAQf9hWFzonUo6bhhjS6toZQd7HZ-pmojtAmag@mail.gmail.com
Discussion: http://postgr.es/m/CA+Tgmobp7+7kmi4gkq7Y+4AM9fTvL+O1oQ4-5gFTT+6Ng-dQ=g@mail.gmail.com
Discussion: http://postgr.es/m/CAFiTN-vTe79M8uDH1yprOU64MNFE+R3ODRuA+JWf27JbhY4hJw@mail.gmail.com
Some routines open-coded the construction of DataRow messages. Use
TupOutputState struct and associated functions instead, which was
already done in some places.
SendTimeLineHistory() is a bit more complicated and isn't converted by
this.
Reviewed-by: Nathan Bossart <nathandbossart@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/7e4fdbdc-699c-4cd0-115d-fb78a957fc22@enterprisedb.com
durable_rename_excl() attempts to avoid overwriting any existing files
by using link() and unlink(), and it falls back to rename() on some
platforms (aka WIN32), which offers no such overwrite protection. Most
callers use durable_rename_excl() just in case there is an existing
file, but in practice there shouldn't be one (see below for more
details).
Furthermore, failures during durable_rename_excl() can result in
multiple hard links to the same file. As per Nathan's tests, it is
possible to end up with two links to the same file in pg_wal after a
crash just before unlink() during WAL recycling. Specifically, the test
produced links to the same file for the current WAL file and the next
one because the half-recycled WAL file was re-recycled upon restarting,
leading to WAL corruption.
This change replaces all the calls of durable_rename_excl() to
durable_rename(). This removes the protection against accidentally
overwriting an existing file, but some platforms are already living
without it and ordinarily there shouldn't be one. The function itself
is left around in case any extensions are using it. It will be removed
on HEAD via a follow-up commit.
Here is a summary of the existing callers of durable_rename_excl() (see
second discussion link at the bottom), replaced by this commit. First,
basic_archive used it to avoid overwriting an archive concurrently
created by another server, but as mentioned above, it will still
overwrite files on some platforms. Second, xlog.c uses it to recycle
past WAL segments, where an overwrite should not happen (origin of the
change at f0e37a8) because there are protections about the WAL segment
to select when recycling an entry. The third and last area is related
to the write of timeline history files. writeTimeLineHistory() will
write a new timeline history file at the end of recovery on promotion,
so there should be no such files for the same timeline.
What remains is writeTimeLineHistoryFile(), that can be used in parallel
by a WAL receiver and the startup process, and some digging of the
buildfarm shows that EEXIST from a WAL receiver can happen with an error
of "could not link file \"pg_wal/xlogtemp.NN\" to \"pg_wal/MM.history\",
which would cause an automatic restart of the WAL receiver as it is
promoted to FATAL, hence this should improve the stability of the WAL
receiver as rename() would overwrite an existing TLI history file
already fetched by the startup process at recovery.
This is a bug fix, but knowing the unlikeliness of the problem involving
one or more crashes at an exceptionally bad moment, no backpatch is
done. Also, I want to be careful with such changes (aaa3aed did the
opposite of this change by removing HAVE_WORKING_LINK so as Windows
would do a link() rather than a rename() but this was not
concurrent-safe). A backpatch could be revisited in the future. This
is the second time this change is attempted, ccfbd92 being the first
one, but this time no assertions are added for the case of a TLI history
file written concurrently by the WAL receiver or the startup process
because we can expect one to exist (some of the TAP tests are able to
trigger with a proper timing).
Author: Nathan Bossart
Reviewed-by: Robert Haas, Kyotaro Horiguchi, Michael Paquier
Discussion: https://postgr.es/m/20220407182954.GA1231544@nathanxps13
Discussion: https://postgr.es/m/Ym6GZbqQdlalSKSG@paquier.xyz
There were many calls to construct_array() and deconstruct_array() for
built-in types, for example, when dealing with system catalog columns.
These all hardcoded the type attributes necessary to pass to these
functions.
To simplify this a bit, add construct_array_builtin(),
deconstruct_array_builtin() as wrappers that centralize this hardcoded
knowledge. This simplifies many call sites and reduces the amount of
hardcoded stuff that is spread around.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/2914356f-9e5f-8c59-2995-5997fc48bcba%40enterprisedb.com
pg_start_backup() and pg_stop_backup() have been respectively renamed to
pg_backup_start() and pg_backup_stop() as of 39969e2, but a few comments
did not get the call.
Reviewed-by: Kyotaro Horiguchi, David Steele
Discussion: https://postgr.es/m/YrqGlj1+4DF3dbZ/@paquier.xyz
MemSet() with a value other than 0 just falls back to memset(), so the
indirection is unnecessary if the value is constant and not 0. Since
there is some interest in getting rid of MemSet(), this gets some easy
cases out of the way. (There are a few MemSet() calls that I didn't
change to maintain the consistency with their surrounding code.)
Discussion: https://www.postgresql.org/message-id/flat/CAEudQApCeq4JjW1BdnwU=m=-DvG5WyUik0Yfn3p6UNphiHjj+w@mail.gmail.com
TransactionIdIsInProgress had a fast path to return 'false' if the
single-item CLOG cache said that the transaction was known to be
committed. However, that was wrong, because a transaction is first
marked as committed in the CLOG but doesn't become visible to others
until it has removed its XID from the proc array. That could lead to an
error:
ERROR: t_xmin is uncommitted in tuple to be updated
or for an UPDATE to go ahead without blocking, before the previous
UPDATE on the same row was made visible.
The window is usually very short, but synchronous replication makes it
much wider, because the wait for synchronous replica happens in that
window.
Another thing that makes it hard to hit is that it's hard to get such
a commit-in-progress transaction into the single item CLOG cache.
Normally, if you call TransactionIdIsInProgress on such a transaction,
it determines that the XID is in progress without checking the CLOG
and without populating the cache. One way to prime the cache is to
explicitly call pg_xact_status() on the XID. Another way is to use a
lot of subtransactions, so that the subxid cache in the proc array is
overflown, making TransactionIdIsInProgress rely on pg_subtrans and
CLOG checks.
This has been broken ever since it was introduced in 2008, but the race
condition is very hard to hit, especially without synchronous
replication. There were a couple of reports of the error starting from
summer 2021, but no one was able to find the root cause then.
TransactionIdIsKnownCompleted() is now unused. In 'master', remove it,
but I left it in place in backbranches in case it's used by extensions.
Also change pg_xact_status() to check TransactionIdIsInProgress().
Previously, it only checked the CLOG, and returned "committed" before
the transaction was actually made visible to other queries. Note that
this also means that you cannot use pg_xact_status() to reproduce the
bug anymore, even if the code wasn't fixed.
Report and analysis by Konstantin Knizhnik. Patch by Simon Riggs, with
the pg_xact_status() change added by me.
Author: Simon Riggs
Reviewed-by: Andres Freund
Discussion: https://www.postgresql.org/message-id/flat/4da7913d-398c-e2ad-d777-f752cf7f0bbb%40garret.ru
This reverts commits 5753d4ee32 and fe60b67250 that modified HOT to
ignore BRIN indexes. The commit message for 5753d4ee32 claims that:
When determining whether an index update may be skipped by using
HOT, we can ignore attributes indexed only by BRIN indexes. There
are no index pointers to individual tuples in BRIN, and the page
range summary will be updated anyway as it relies on visibility
info.
This is partially incorrect - it's true BRIN indexes don't point to
individual tuples, so HOT chains are not an issue, but the visibitlity
info is not sufficient to keep the index up to date. This can easily
result in corrupted indexes, as demonstrated in the hackers thread.
This does not mean relaxing the HOT restrictions for BRIN is a lost
cause, but it needs to handle the two aspects (allowing HOT chains and
updating the page range summaries) as separate. But that requires a
major changes, and it's too late for that in the current dev cycle.
Reported-by: Tomas Vondra
Discussion: https://postgr.es/m/05ebcb44-f383-86e3-4f31-0a97a55634cf@enterprisedb.com
The original advice for hard-wired SetConfigOption calls was to use
PGC_S_OVERRIDE, particularly for PGC_INTERNAL GUCs. However,
that's really overkill for PGC_INTERNAL GUCs, since there is no
possibility that we need to override a user-provided setting.
Instead use PGC_S_DYNAMIC_DEFAULT in most places, so that the
value will appear with source = 'default' in pg_settings and thereby
not be shown by psql's new \dconfig command. The one exception is
that when changing in_hot_standby in a hot-standby session, we still
use PGC_S_OVERRIDE, because people felt that seeing that in \dconfig
would be a good thing.
Similarly use PGC_S_DYNAMIC_DEFAULT for the auto-tune value of
wal_buffers (if possible, that is if wal_buffers wasn't explicitly
set to -1), and for the typical 2MB value of max_stack_depth.
In combination these changes remove four not-very-interesting
entries from the typical output of \dconfig, all of which people
fingered as "why is that showing up?" in the discussion thread.
Discussion: https://postgr.es/m/3118455.1649267333@sss.pgh.pa.us
David Rowley
Peter Eisentraut
Thomas Munro
Michael Paquier
Peter Geoghegan
Tom Lane
Robert Haas
John Naylor
Tomas Vondra
Alvaro Herrera
Daniel Gustafsson
Amit Kapila
Fujii Masao
Heikki Linnakangas