Previously, a worker process would establish values for these based on
its own start time. In v10 and up, this can trivially be shown to cause
misbehavior of transaction_timestamp(), timestamp_in(), and related
functions which are (perhaps unwisely?) marked parallel-safe. It seems
likely that other behaviors might diverge from what happens in the parent
as well.
It's not as trivial to demonstrate problems in 9.6 or 9.5, but I'm sure
it's still possible, so back-patch to all branches containing parallel
worker infrastructure.
In HEAD only, mark now() and statement_timestamp() as parallel-safe
(other affected functions already were). While in theory we could
still squeeze that change into v11, it doesn't seem important enough
to force a last-minute catversion bump.
Konstantin Knizhnik, whacked around a bit by me
Discussion: https://postgr.es/m/6406dbd2-5d37-4cb6-6eb2-9c44172c7e7c@postgrespro.ru
Commit 9da0cc35284, which introduced parallel CREATE INDEX, failed to
propagate relmapper.c backend local cache state to parallel worker
processes. This could result in parallel index builds against mapped
catalog relations where the leader process (participating as a worker)
scans the new, pristine relfilenode, while worker processes scan the
obsolescent relfilenode. When this happened, the final index structure
was typically not consistent with the owning table's structure. The
final index structure could contain entries formed from both heap
relfilenodes. Only rebuilds on mapped catalog relations that occur as
part of a VACUUM FULL or CLUSTER could become corrupt in practice, since
their mapped relation relfilenode swap is what allows the inconsistency
to arise.
On master, fix the problem by propagating the required relmapper.c
backend state as part of standard parallel initialization (Cf. commit
29d58fd3). On v11, simply disallow builds against mapped catalog
relations by deeming them parallel unsafe.
Author: Peter Geoghegan
Reported-By: "death lock"
Reviewed-By: Tom Lane, Amit Kapila
Bug: #15309
Discussion: https://postgr.es/m/153329671686.1405.18298309097348420351@wrigleys.postgresql.org
Backpatch: 11-, where parallel CREATE INDEX was introduced.
Since the old logic was completely unaware of subtransactions, a
change made in a subsequently-aborted subtransaction would still cause
workers to be stopped at toplevel transaction commit. Fix that by
managing a stack of worker lists rather than just one.
Amit Khandekar and Robert Haas
Discussion: http://postgr.es/m/CAJ3gD9eaG_mWqiOTA2LfAug-VRNn1hrhf50Xi1YroxL37QkZNg@mail.gmail.com
When multiple relations are deleted at the same transaction,
the files of those relations are deleted by one call to smgrdounlinkall(),
which leads to scan whole shared_buffers only one time. OTOH,
previously, during recovery, smgrdounlink() (not smgrdounlinkall()) was
called for each file to delete, which led to scan shared_buffers
multiple times. Obviously this could cause to increase the WAL replay
time very much especially when shared_buffers was huge.
To alleviate this situation, this commit changes the recovery so that
it also calls smgrdounlinkall() only one time to delete multiple
relation files.
This is just fix for oversight of commit 279628a0a7, not new feature.
So, per discussion on pgsql-hackers, we concluded to backpatch this
to all supported versions.
Author: Fujii Masao
Reviewed-by: Michael Paquier, Andres Freund, Thomas Munro, Kyotaro Horiguchi, Takayuki Tsunakawa
Discussion: https://postgr.es/m/CAHGQGwHVQkdfDqtvGVkty+19cQakAydXn1etGND3X0PHbZ3+6w@mail.gmail.com
Issues relate only to subtransactions that hold AccessExclusiveLocks
when replayed on standby.
Prior to PG10, aborting subtransactions that held an
AccessExclusiveLock failed to release the lock until top level commit or
abort. 49bff5300d527 fixed that.
However, 49bff5300d527 also introduced a similar bug where subtransaction
commit would fail to release an AccessExclusiveLock, leaving the lock to
be removed sometimes early and sometimes late. This commit fixes
that bug also. Backpatch to PG10 needed.
Tested by observation. Note need for multi-node isolationtester to improve
test coverage for this and other HS cases.
Reported-by: Simon Riggs
Author: Simon Riggs
Commit 1eb6d6527aae introduced zeroed alignment bytes in the GID field
of commit/abort WAL records. Fixup commit cf5a1890592b later changed
that representation into a regular cstring with a single terminating
zero byte, but it also introduced an off-by-one mistake. Fix that.
Author: Nikhil Sontakke
Reported-by: Nikhil Sontakke
Discussion: https://postgr.es/m/CAMGcDxey6dG1DP34_tJMoWPcp5sPJUAL4K5CayUUXLQSx2GQpA@mail.gmail.com
This change makes this module act more like most of our other low-level
resource management modules. It's a caller error if something is not
explicitly closed by the end of a successful transaction, so issue
a WARNING about it. This would not actually have caught the file leak
bug fixed in commit 231bcd080, because that was in a transaction-abort
path; but it still seems like a good, and pretty cheap, cross-check.
Discussion: https://postgr.es/m/152056616579.4966.583293218357089052@wrigleys.postgresql.org
Review of commit 1eb6d652: It's pointless to add padding to the GID fields,
when the code that follows assumes that there is no alignment, and uses
memcpy(). Remove the pointless padding.
Update comments to note the new fields in the WAL records.
Reviewed-by: Michael Paquier
Discussion: https://www.postgresql.org/message-id/33b787bf-dc20-1161-54e9-3f3b607bf59d%40iki.fi
In commit 9c0a0de4c, I'd failed to notice that catalog/catalog.h
should also be considered a frontend-unsafe header, because it includes
(and needs) the full form of pg_class.h, not to mention relcache.h.
However, various frontend code was depending on it to get
TABLESPACE_VERSION_DIRECTORY, so refactoring of some sort is called for.
The cleanest answer seems to be to move TABLESPACE_VERSION_DIRECTORY,
as well as the OIDCHARS symbol, to common/relpath.h. Do that, and mop up
inclusions as necessary. (I found that quite a few current users of
catalog/catalog.h don't seem to need it at all anymore, apparently as a
result of the refactorings that created common/relpath.[hc]. And
initdb.c needed it only as a route to pg_class_d.h.)
Discussion: https://postgr.es/m/6629.1523294509@sss.pgh.pa.us
Store GID of 2PC in commit/abort WAL records when wal_level = logical.
This allows logical decoding to send the SAME gid to subscribers
across restarts of logical replication.
Track relica origin replay progress for 2PC.
(Edited from patch 0003 in the logical decoding 2PC series.)
Authors: Nikhil Sontakke, Stas Kelvich
Reviewed-by: Simon Riggs, Andres Freund
Originally, we treated memory context names as potentially variable in
all cases, and therefore always copied them into the context header.
Commit 9fa6f00b1 rethought this a little bit and invented a distinction
between fixed and variable names, skipping the copy step for the former.
But we can make things both simpler and more useful by instead allowing
there to be two parts to a context's identification, a fixed "name" and
an optional, variable "ident". The name supplied in the context create
call is now required to be a compile-time-constant string in all cases,
as it is never copied but just pointed to. The "ident" string, if
wanted, is supplied later. This is needed because typically we want
the ident to be stored inside the context so that it's cleaned up
automatically on context deletion; that means it has to be copied into
the context before we can set the pointer.
The cost of this approach is basically just an additional pointer field
in struct MemoryContextData, which isn't much overhead, and is bought
back entirely in the AllocSet case by not needing a headerSize field
anymore, since we no longer have to cope with variable header length.
In addition, we can simplify the internal interfaces for memory context
creation still further, saving a few cycles there. And it's no longer
true that a custom identifier disqualifies a context from participating
in aset.c's freelist scheme, so possibly there's some win on that end.
All the places that were using non-compile-time-constant context names
are adjusted to put the variable info into the "ident" instead. This
allows more effective identification of those contexts in many cases;
for example, subsidary contexts of relcache entries are now identified
by both type (e.g. "index info") and relname, where before you got only
one or the other. Contexts associated with PL function cache entries
are now identified more fully and uniformly, too.
I also arranged for plancache contexts to use the query source string
as their identifier. This is basically free for CachedPlanSources, as
they contained a copy of that string already. We pay an extra pstrdup
to do it for CachedPlans. That could perhaps be avoided, but it would
make things more fragile (since the CachedPlanSource is sometimes
destroyed first). I suspect future improvements in error reporting will
require CachedPlans to have a copy of that string anyway, so it's not
clear that it's worth moving mountains to avoid it now.
This also changes the APIs for context statistics routines so that the
context-specific routines no longer assume that output goes straight
to stderr, nor do they know all details of the output format. This
is useful immediately to reduce code duplication, and it also allows
for external code to do something with stats output that's different
from printing to stderr.
The reason for pushing this now rather than waiting for v12 is that
it rethinks some of the API changes made by commit 9fa6f00b1. Seems
better for extension authors to endure just one round of API changes
not two.
Discussion: https://postgr.es/m/CAB=Je-FdtmFZ9y9REHD7VsSrnCkiBhsA4mdsLKSPauwXtQBeNA@mail.gmail.com
In some cases, these were different for no apparent reason, making
debugging unnecessarily mysterious.
Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Instead of embedding the savepoint name in a list and then requiring
complex code to unpack it, just add another struct field to store it
directly.
Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
We call this thing a "transaction block" everywhere except in a few
functions, where it is mysteriously called a "transaction chain". In
the SQL standard, a transaction chain is something different. So rename
these functions to match the common terminology.
Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
currentCommandIdUsed is only used to skip redundant increments of the
command counter, and CommandCounterIncrement() is categorically denied
under parallelism anyway. Therefore, it's OK for
GetCurrentCommandId() to mark the counter value used, as long as it
happens in the leader, not a worker.
Prior to commit e9baa5e9fa147e00a2466ab2c40eb99c8a700824, the slightly
incorrect check didn't matter, but now it does. A test case added by
commit 1804284042e659e7d16904e7bbb0ad546394b6a3 uncovered the problem
by accident; it caused failures with force_parallel_mode=on/regress.
Report and review by Andres Freund. Patch by me.
Discussion: http://postgr.es/m/20171221143106.5lhtygohvmazli3x@alap3.anarazel.de
Generally, error recovery paths that need to do things like
LWLockReleaseAll and pgstat_report_wait_end also need to call
ConditionVariableCancelSleep, but AbortSubTransaction was missed.
Since subtransaction abort might destroy up the DSM segment that
contains the ConditionVariable stored in cv_sleep_target, this
can result in a crash for anything using condition variables.
Reported and diagnosed by Andres Freund.
Discussion: http://postgr.es/m/20171221110048.rxk6464azzl5t2fi@alap3.anarazel.de
This patch makes a number of interrelated changes to reduce the overhead
involved in creating/deleting memory contexts. The key ideas are:
* Include the AllocSetContext header of an aset.c context in its first
malloc request, rather than allocating it separately in TopMemoryContext.
This means that we now always create an initial or "keeper" block in an
aset, even if it never receives any allocation requests.
* Create freelists in which we can save and recycle recently-destroyed
asets (this idea is due to Robert Haas).
* In the common case where the name of a context is a constant string,
just store a pointer to it in the context header, rather than copying
the string.
The first change eliminates a palloc/pfree cycle per context, and
also avoids bloat in TopMemoryContext, at the price that creating
a context now involves a malloc/free cycle even if the context never
receives any allocations. That would be a loser for some common
usage patterns, but recycling short-lived contexts via the freelist
eliminates that pain.
Avoiding copying constant strings not only saves strlen() and strcpy()
overhead, but is an essential part of the freelist optimization because
it makes the context header size constant. Currently we make no
attempt to use the freelist for contexts with non-constant names.
(Perhaps someday we'll need to think harder about that, but in current
usage, most contexts with custom names are long-lived anyway.)
The freelist management in this initial commit is pretty simplistic,
and we might want to refine it later --- but in common workloads that
will never matter because the freelists will never get full anyway.
To create a context with a non-constant name, one is now required to
call AllocSetContextCreateExtended and specify the MEMCONTEXT_COPY_NAME
option. AllocSetContextCreate becomes a wrapper macro, and it includes
a test that will complain about non-string-literal context name
parameters on gcc and similar compilers.
An unfortunate side effect of making AllocSetContextCreate a macro is
that one is now *required* to use the size parameter abstraction macros
(ALLOCSET_DEFAULT_SIZES and friends) with it; the pre-9.6 habit of
writing out individual size parameters no longer works unless you
switch to AllocSetContextCreateExtended.
Internally to the memory-context-related modules, the context creation
APIs are simplified, removing the rather baroque original design whereby
a context-type module called mcxt.c which then called back into the
context-type module. That saved a bit of code duplication, but not much,
and it prevented context-type modules from exercising control over the
allocation of context headers.
In passing, I converted the test-and-elog validation of aset size
parameters into Asserts to save a few more cycles. The original thought
was that callers might compute size parameters on the fly, but in practice
nobody does that, so it's useless to expend cycles on checking those
numbers in production builds.
Also, mark the memory context method-pointer structs "const",
just for cleanliness.
Discussion: https://postgr.es/m/2264.1512870796@sss.pgh.pa.us
The lower case spellings are C and C++ standard and are used in most
parts of the PostgreSQL sources. The upper case spellings are only used
in some files/modules. So standardize on the standard spellings.
The APIs for ICU, Perl, and Windows define their own TRUE and FALSE, so
those are left as is when using those APIs.
In code comments, we use the lower-case spelling for the C concepts and
keep the upper-case spelling for the SQL concepts.
Reviewed-by: Michael Paquier <michael.paquier@gmail.com>
resowner/README contained advice to use a PG_TRY block to restore the
old CurrentResourceOwner value anywhere that that variable is transiently
changed. That advice was only inconsistently followed, however, and
on reflection it seems like unnecessary overhead. We don't bother
with such a convention for transient CurrentMemoryContext changes,
on the grounds that any (sub)transaction abort will start out by
resetting CurrentMemoryContext to what it wants. But the same is
true of CurrentResourceOwner, so there seems no need to treat it
differently.
Hence, remove PG_TRY blocks that exist only to restore CurrentResourceOwner
before re-throwing the error. There are a couple of places that restore
it along with some other actions, and I left those alone; the restore is
probably unnecessary but no noticeable gain will result from removing it.
Discussion: https://postgr.es/m/5236.1507583529@sss.pgh.pa.us
This reverts commit 15bc038f9, along with the followon commits 1635e80d3
and 984c92074 that tried to clean up the problems exposed by bug #14825.
The result was incomplete because it failed to address parallel-query
requirements. With 10.0 release so close upon us, now does not seem like
the time to be adding more code to fix that. I hope we can un-revert this
code and add the missing parallel query support during the v11 cycle.
Back-patch to v10.
Discussion: https://postgr.es/m/20170922185904.1448.16585@wrigleys.postgresql.org
Commit 15bc038f9 allowed ALTER TYPE ADD VALUE to be executed inside
transaction blocks, by disallowing the use of the added value later
in the same transaction, except under limited circumstances. However,
the test for "limited circumstances" was heuristic and could reject
references to enum values that were created during CREATE TYPE AS ENUM,
not just later. This breaks the use-case of restoring pg_dump scripts
in a single transaction, as reported in bug #14825 from Balazs Szilfai.
We can improve this by keeping a "blacklist" table of enum value OIDs
created by ALTER TYPE ADD VALUE during the current transaction. Any
visible-but-uncommitted value whose OID is not in the blacklist must
have been created by CREATE TYPE AS ENUM, and can be used safely
because it could not have a lifespan shorter than its parent enum type.
This change also removes the restriction that a renamed enum value
can't be used before being committed (unless it was on the blacklist).
Andrew Dunstan, with cosmetic improvements by me.
Back-patch to v10.
Discussion: https://postgr.es/m/20170922185904.1448.16585@wrigleys.postgresql.org
It is equivalent in ANSI C to write (*funcptr) () and funcptr(). These
two styles have been applied inconsistently. After discussion, we'll
use the more verbose style for plain function pointer variables, to make
it clear that it's a variable, and the shorter style when the function
pointer is in a struct (s.func() or s->func()), because then it's clear
that it's not a plain function name, and otherwise the excessive
punctuation makes some of those invocations hard to read.
Discussion: https://www.postgresql.org/message-id/f52c16db-14ed-757d-4b48-7ef360b1631d@2ndquadrant.com
Issuing a savepoint-related command in a Query message that contains
multiple SQL statements led to a FATAL exit with a complaint about
"unexpected state STARTED". This is a shortcoming of commit 4f896dac1,
which attempted to prevent such misbehaviors in multi-statement strings;
its quick hack of marking the individual statements as "not top-level"
does the wrong thing in this case, and isn't a very accurate description
of the situation anyway.
To fix, let's introduce into xact.c an explicit model of what happens for
multi-statement Query strings. This is an "implicit transaction block
in progress" state, which for many purposes works like the normal
TBLOCK_INPROGRESS state --- in particular, IsTransactionBlock returns true,
causing the desired result that PreventTransactionChain will throw error.
But in case of error abort it works like TBLOCK_STARTED, allowing the
transaction to be cancelled without need for an explicit ROLLBACK command.
Commit 4f896dac1 is reverted in toto, so that we go back to treating the
individual statements as "top level". We could have left it as-is, but
this allows sharpening the error message for PreventTransactionChain
calls inside functions.
Except for getting a normal error instead of a FATAL exit for savepoint
commands, this patch should result in no user-visible behavioral change
(other than that one error message rewording). There are some things
we might want to do in the line of changing the appearance or wording of
error and warning messages around this behavior, which would be much
simpler to do now that it's an explicitly modeled state. But I haven't
done them here.
Although this fixes a long-standing bug, no backpatch. The consequences
of the bug don't seem severe enough to justify the risk that this commit
itself creates some new issue.
Patch by me, but it owes something to previous investigation by
Takayuki Tsunakawa, who also reported the bug in the first place.
Also thanks to Michael Paquier for reviewing.
Discussion: https://postgr.es/m/0A3221C70F24FB45833433255569204D1F6BE40D@G01JPEXMBYT05
Stress testing by Andreas Seltenreich disclosed longstanding problems that
occur if a FATAL exit (e.g. due to receipt of SIGTERM) occurs while we are
trying to execute a ROLLBACK of an already-failed transaction. In such a
case, xact.c is in TBLOCK_ABORT state, so that AbortOutOfAnyTransaction
would skip AbortTransaction and go straight to CleanupTransaction. This
led to an assert failure in an assert-enabled build (due to the ROLLBACK's
portal still having a cleanup hook) or without assertions, to a FATAL exit
complaining about "cannot drop active portal". The latter's not
disastrous, perhaps, but it's messy enough to want to improve it.
We don't really want to run all of AbortTransaction in this code path.
The minimum required to clean up the open portal safely is to do
AtAbort_Memory and AtAbort_Portals. It seems like a good idea to
do AtAbort_Memory unconditionally, to be entirely sure that we are
starting with a safe CurrentMemoryContext. That means that if the
main loop in AbortOutOfAnyTransaction does nothing, we need an extra
step at the bottom to restore CurrentMemoryContext = TopMemoryContext,
which I chose to do by invoking AtCleanup_Memory. This'll result in
calling AtCleanup_Memory twice in many of the paths through this function,
but that seems harmless and reasonably inexpensive.
The original motivation for the assertion in AtCleanup_Portals was that
we wanted to be sure that any user-defined code executed as a consequence
of the cleanup hook runs during AbortTransaction not CleanupTransaction.
That still seems like a valid concern, and now that we've seen one case
of the assertion firing --- which means that exactly that would have
happened in a production build --- let's replace the Assert with a runtime
check. If we see the cleanup hook still set, we'll emit a WARNING and
just drop the hook unexecuted.
This has been like this a long time, so back-patch to all supported
branches.
Discussion: https://postgr.es/m/877ey7bmun.fsf@ansel.ydns.eu
The sole useful effect of this function, to check that no catcache
entries have positive refcounts at transaction end, has really been
obsolete since we introduced ResourceOwners in PG 8.1. We reduced the
checks to assertions years ago, so that the function was a complete
no-op in production builds. There have been previous discussions about
removing it entirely, but consensus up to now was that it had some small
value as a cross-check for bugs in the ResourceOwner logic.
However, it now emerges that it's possible to trigger these assertions
if you hit an assert-enabled backend with SIGTERM during a call to
SearchCatCacheList, because that function temporarily increases the
refcounts of entries it's intending to add to a catcache list construct.
In a normal ERROR scenario, the extra refcounts are cleaned up by
SearchCatCacheList's PG_CATCH block; but in a FATAL exit we do a
transaction abort and exit without ever executing PG_CATCH handlers.
There's a case to be made that this is a generic hazard and we should
consider restructuring elog(FATAL) handling so that pending PG_CATCH
handlers do get run. That's pretty scary though: it could easily create
more problems than it solves. Preliminary stress testing by Andreas
Seltenreich suggests that there are not many live problems of this ilk,
so we rejected that idea.
There are more-localized ways to fix the problem; the most principled
one would be to use PG_ENSURE_ERROR_CLEANUP instead of plain PG_TRY.
But adding cycles to SearchCatCacheList isn't very appealing. We could
also weaken the assertions in AtEOXact_CatCache in some more or less
ad-hoc way, but that just makes its raison d'etre even less compelling.
In the end, the most reasonable solution seems to be to just remove
AtEOXact_CatCache altogether, on the grounds that it's not worth trying
to fix it. It hasn't found any bugs for us in many years.
Per report from Jeevan Chalke. Back-patch to all supported branches.
Discussion: https://postgr.es/m/CAM2+6=VEE30YtRQCZX7_sCFsEpoUkFBV1gZazL70fqLn8rcvBA@mail.gmail.com
Don't move parenthesized lines to the left, even if that means they
flow past the right margin.
By default, BSD indent lines up statement continuation lines that are
within parentheses so that they start just to the right of the preceding
left parenthesis. However, traditionally, if that resulted in the
continuation line extending to the right of the desired right margin,
then indent would push it left just far enough to not overrun the margin,
if it could do so without making the continuation line start to the left of
the current statement indent. That makes for a weird mix of indentations
unless one has been completely rigid about never violating the 80-column
limit.
This behavior has been pretty universally panned by Postgres developers.
Hence, disable it with indent's new -lpl switch, so that parenthesized
lines are always lined up with the preceding left paren.
This patch is much less interesting than the first round of indent
changes, but also bulkier, so I thought it best to separate the effects.
Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org
Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
Change pg_bsd_indent to follow upstream rules for placement of comments
to the right of code, and remove pgindent hack that caused comments
following #endif to not obey the general rule.
Commit e3860ffa4dd0dad0dd9eea4be9cc1412373a8c89 wasn't actually using
the published version of pg_bsd_indent, but a hacked-up version that
tried to minimize the amount of movement of comments to the right of
code. The situation of interest is where such a comment has to be
moved to the right of its default placement at column 33 because there's
code there. BSD indent has always moved right in units of tab stops
in such cases --- but in the previous incarnation, indent was working
in 8-space tab stops, while now it knows we use 4-space tabs. So the
net result is that in about half the cases, such comments are placed
one tab stop left of before. This is better all around: it leaves
more room on the line for comment text, and it means that in such
cases the comment uniformly starts at the next 4-space tab stop after
the code, rather than sometimes one and sometimes two tabs after.
Also, ensure that comments following #endif are indented the same
as comments following other preprocessor commands such as #else.
That inconsistency turns out to have been self-inflicted damage
from a poorly-thought-through post-indent "fixup" in pgindent.
This patch is much less interesting than the first round of indent
changes, but also bulkier, so I thought it best to separate the effects.
Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org
Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
The optimized code in 728bd991c3c4 contains a few invalid locking
sequences. To wit, the original code would try to acquire an lwlock
that it already holds. Avoid this by moving lock acquisitions to
higher-level code, and install appropriate assertions in low-level that
the correct mode is held.
Authors: Michael Paquier, Álvaro Herrera
Reported-By: chuanting wang
Bug: #14680
Discussion: https://postgr.es/m/20170531033228.1487.10124@wrigleys.postgresql.org
After the logical replication launcher was told to wake up at
commit (for example, by a CREATE SUBSCRIPTION command), the flag to wake
up was not reset, so it would be woken up at every following commit as
well. So fix that by resetting the flag.
Also, we don't need to wake up anything if the transaction was rolled
back. Just reset the flag in that case.
Author: Masahiko Sawada <sawada.mshk@gmail.com>
Reported-by: Fujii Masao <masao.fujii@gmail.com>
The bug fixed by 0874d4f3e183757ba15a4b3f3bf563e0393dd9c2
caused us to question and rework the handling of
subtransactions in 2PC during and at end of recovery.
Patch adds checks and tests to ensure no further bugs.
This effectively removes the temporary measure put in place
by 546c13e11b29a5408b9d6a6e3cca301380b47f7f.
Author: Simon Riggs
Reviewed-by: Tom Lane, Michael Paquier
Discussion: http://postgr.es/m/CANP8+j+vvXmruL_i2buvdhMeVv5TQu0Hm2+C5N+kdVwHJuor8w@mail.gmail.com
For normal commits and aborts we already reset PgXact->xmin,
so we can simply avoid running SnapshotResetXmin() twice.
During performance tests by Alexander Korotkov, diagnosis
by Andres Freund showed PgXact array as a bottleneck. After
manual analysis by me of the code paths that touch those
memory locations, I was able to identify extraneous code
in the main transaction commit path.
Avoiding touching highly contented shmem improves concurrent
performance slightly on all workloads, confirmed by tests
run by Ashutosh Sharma and Alexander Korotkov.
Simon Riggs
Discussion: CANP8+jJdXE9b+b9F8CQT-LuxxO0PBCB-SZFfMVAdp+akqo4zfg@mail.gmail.com
2PC state info held in shmem at PREPARE, then cleaned at COMMIT PREPARED/ABORT PREPARED,
avoiding writing/fsyncing any state information to disk in the normal path, greatly enhancing replay speed.
Prepared transactions that live past one checkpoint redo horizon will be written to disk as now.
Similar conceptually to 978b2f65aa1262eb4ecbf8b3785cb1b9cf4db78e and building upon
the infrastructure created by that commit.
Authors, in equal measure: Stas Kelvich, Nikhil Sontakke and Michael Paquier
Discussion: https://postgr.es/m/CAMGcDxf8Bn9ZPBBJZba9wiyQq-Qk5uqq=VjoMnRnW5s+fKST3w@mail.gmail.com
A hot standby replica keeps a list of Access Exclusive locks for a top
level transaction. These locks are released when the top level transaction
ends. Searching of this list is O(N^2), and each transaction had to pay the
price of searching this list for locks, even if it didn't take any AE
locks itself.
This patch optimizes this case by having the master server track which
transactions took AE locks, and passes that along to the standby server in
the commit/abort record. This allows the standby to only try to release
locks for transactions which actually took any, avoiding the majority of
the performance issue.
Refactor MyXactAccessedTempRel into MyXactFlags to allow minimal additional
cruft with this.
Analysis and initial patch by David Rowley
Author: David Rowley and Simon Riggs
