After further review, we want to move in the direction of always
quoting GUC names in error messages, rather than the previous (PG16)
wildly mixed practice or the intermittent (mid-PG17) idea of doing
this depending on how possibly confusing the GUC name is.
This commit applies appropriate quotes to (almost?) all mentions of
GUC names in error messages. It partially supersedes a243569bf6 and
8d9978a717, which had moved things a bit in the opposite direction
but which then were abandoned in a partial state.
Author: Peter Smith <smithpb2250@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CAHut%2BPv-kSN8SkxSdoHano_wPubqcg5789ejhCDZAcLFceBR-w%40mail.gmail.com
Specifically, it terminates a background worker even if the caller
couldn't terminate the background worker with pg_terminate_backend().
Commit 3a9b18b309 neglected to update
this. Back-patch to v13, which introduced DROP DATABASE FORCE.
Reviewed by Amit Kapila. Reported by Kirill Reshke.
Discussion: https://postgr.es/m/20240429212756.60.nmisch@google.com
This fixes various typos, duplicated words, and tiny bits of whitespace
mainly in code comments but also in docs.
Author: Daniel Gustafsson <daniel@yesql.se>
Author: Heikki Linnakangas <hlinnaka@iki.fi>
Author: Alexander Lakhin <exclusion@gmail.com>
Author: David Rowley <dgrowleyml@gmail.com>
Author: Nazir Bilal Yavuz <byavuz81@gmail.com>
Discussion: https://postgr.es/m/3F577953-A29E-4722-98AD-2DA9EFF2CBB8@yesql.se
GlobalVisTestNonRemovableHorizon() was only used for the implementation of
snapshot_too_old, which was removed in f691f5b80a. As using
GlobalVisTestNonRemovableHorizon() is not particularly efficient, no new uses
for it should be added. Therefore remove.
Discussion: https://postgr.es/m/20240415185720.q4dg4dlcyvvrabz4@awork3.anarazel.de
GetPageWithFreeSpace() callers assume the returned block exists in the
main fork, failing with "could not read block" errors if that doesn't
hold. Make that assumption reliable now. It hadn't been guaranteed,
due to the weak WAL and data ordering of participating components. Most
operations on the fsm fork are not WAL-logged. Relation extension is
not WAL-logged. Hence, an fsm-fork block on disk can reference a
main-fork block that no WAL record has initialized. That could happen
after an OS crash, a replica promote, or a PITR restore. wal_log_hints
makes the trouble easier to hit; a replica promote or PITR ending just
after a relevant fsm-fork FPI_FOR_HINT may yield this broken state. The
v16 RelationAddBlocks() mechanism also makes the trouble easier to hit,
since it bulk-extends even without extension lock waiters. Commit
917dc7d239 stopped trouble around
truncation, but vectors involving PageIsNew() pages remained.
This implementation adds a RelationGetNumberOfBlocks() call when the
cached relation size doesn't confirm a block exists. We've been unable
to identify a benchmark that slows materially, but this may show up as
additional time in lseek(). An alternative without that overhead would
be a new ReadBufferMode such that ReadBufferExtended() returns NULL
after a 0-byte read, with all other errors handled normally. However,
each GetFreeIndexPage() caller would then need code for the return-NULL
case. Back-patch to v14, due to earlier versions not caching relation
size and the absence of a pre-v16 problem report.
Ronan Dunklau. Reported by Ronan Dunklau.
Discussion: https://postgr.es/m/1878547.tdWV9SEqCh%40aivenlaptop
When testing buffer pool logic, it is useful to be able to evict
arbitrary blocks. This function can be used in SQL queries over the
pg_buffercache view to set up a wide range of buffer pool states. Of
course, buffer mappings might change concurrently so you might evict a
block other than the one you had in mind, and another session might
bring it back in at any time. That's OK for the intended purpose of
setting up developer testing scenarios, and more complicated interlocking
schemes to give stronger guararantees about that would likely be less
flexible for actual testing work anyway. Superuser-only.
Author: Palak Chaturvedi <chaturvedipalak1911@gmail.com>
Author: Thomas Munro <thomas.munro@gmail.com> (docs, small tweaks)
Reviewed-by: Nitin Jadhav <nitinjadhavpostgres@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Cary Huang <cary.huang@highgo.ca>
Reviewed-by: Cédric Villemain <cedric.villemain+pgsql@abcsql.com>
Reviewed-by: Jim Nasby <jim.nasby@gmail.com>
Reviewed-by: Maxim Orlov <orlovmg@gmail.com>
Reviewed-by: Thomas Munro <thomas.munro@gmail.com>
Reviewed-by: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://postgr.es/m/CALfch19pW48ZwWzUoRSpsaV9hqt0UPyaBPC4bOZ4W+c7FF566A@mail.gmail.com
When we determine that a wanted block can't be combined with the current
pending read, it's time to start that read to get it out of the way. An
"if" in that code path should have been a "while", because it might take
more than one go in case of partial reads. This was only broken for
smaller ranges, as the more common case of io_combine_limit-sized ranges
is handled earlier in the code and knows how to loop, hiding the bug for
a while.
Discovered while testing large parallel sequential scans of partially
cached tables. The ramp-up-and-down block allocator for parallel scans
could hit the problem case and skip some blocks near the end that should
have been streamed.
Defect in commit b5a9b18c.
Discussion: https://postgr.es/m/CA%2BhUKG%2Bh8Whpv0YsJqjMVkjYX%2B80fTVc6oi-V%2BzxJvykLpLHYQ%40mail.gmail.com
The BAS_VACUUM ring size has been 256kB since commit d526575f introduced
the mechanism 17 years ago. Commit 1cbbee03 recently made it
configurable but retained the traditional default. The correct default
size has been debated for years, but 256kB is certainly very small.
VACUUM soon needs to write back data it dirtied only 32 blocks ago,
which usually requires flushing the WAL. New experiments in prefetching
pages for VACUUM exacerbated the problem by crashing into dirty data
even sooner. Let's make the default 2MB. That's 1.6% of the default
toy buffer pool size, and 0.2% of 1GB, which would be a considered a
small shared_buffers setting for a real system these days. Users are
still free to set the GUC to a different value.
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/20240403221257.md4gfki3z75cdyf6%40awork3.anarazel.de
Discussion: https://postgr.es/m/CA%2BhUKGLY4Q4ZY4f1rvnFtv6%2BPkjNf8MejdPkcju3Qii9DYqqcQ%40mail.gmail.com
While pinning extra buffers to look ahead, users of strategies are in
danger of using too many buffers. For some strategies, that means
"escaping" from the ring, and in others it means forcing dirty data to
disk very frequently with associated WAL flushing. Since external code
has no insight into any of that, allow individual strategy types to
expose a clamp that should be applied when deciding how many buffers to
pin at once.
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://postgr.es/m/CAAKRu_aJXnqsyZt6HwFLnxYEBgE17oypkxbKbT1t1geE_wvH2Q%40mail.gmail.com
The "fast path" for well cached scans that don't do any I/O was
accidentally coded in a way that could only be triggered by pg_prewarm's
usage pattern, which starts out with a higher distance because of the
flags it passes in. We want it to work for streaming sequential scans
too, once that patch is committed. Adjust.
Reviewed-by: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://postgr.es/m/CA%2BhUKGKXZALJ%3D6aArUsXRJzBm%3Dqvc4AWp7%3DiJNXJQqpbRLnD_w%40mail.gmail.com
Execute both freezing and pruning of tuples in the same
heap_page_prune() function, now called heap_page_prune_and_freeze(),
and emit a single WAL record containing all changes. That reduces the
overall amount of WAL generated.
This moves the freezing logic from vacuumlazy.c to the
heap_page_prune_and_freeze() function. The main difference in the
coding is that in vacuumlazy.c, we looked at the tuples after the
pruning had already happened, but in heap_page_prune_and_freeze() we
operate on the tuples before pruning. The heap_prepare_freeze_tuple()
function is now invoked after we have determined that a tuple is not
going to be pruned away.
VACUUM no longer needs to loop through the items on the page after
pruning. heap_page_prune_and_freeze() does all the work. It now
returns the list of dead offsets, including existing LP_DEAD items, to
the caller. Similarly it's now responsible for tracking 'all_visible',
'all_frozen', and 'hastup' on the caller's behalf.
Author: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://www.postgresql.org/message-id/20240330055710.kqg6ii2cdojsxgje@liskov
Bug in commit 53c2a97a9266: we failed to acquire the correct SLRU bank
lock when iterating to zero-out intermediate pages in predicate.c.
Rewrite the code block so that we follow the locking protocol correctly.
Also update an outdated comment in the same file -- SerialSLRULock
exists no more.
Reported-by: Alexander Lakhin <exclusion@gmail.com>
Reviewed-by: Dilip Kumar <dilipbalaut@gmail.com>
Discussion: https://postgr.es/m/2a25eaf4-a3a4-5fd1-6241-9d7c73142085@gmail.com
Previously, binaryheap didn't support updating a key and removing a
node in an efficient way. For example, in order to remove a node from
the binaryheap, the caller had to pass the node's position within the
array that the binaryheap internally has. Removing a node from the
binaryheap is done in O(log n) but searching for the key's position is
done in O(n).
This commit adds a hash table to binaryheap in order to track the
position of each nodes in the binaryheap. That way, by using newly
added functions such as binaryheap_update_up() etc., both updating a
key and removing a node can be done in O(1) on an average and O(log n)
in worst case. This is known as the indexed binary heap. The caller
can specify to use the indexed binaryheap by passing indexed = true.
The current code does not use the new indexing logic, but it will be
used by an upcoming patch.
Reviewed-by: Vignesh C, Peter Smith, Hayato Kuroda, Ajin Cherian,
Tomas Vondra, Shubham Khanna
Discussion: https://postgr.es/m/CAD21AoDffo37RC-eUuyHJKVEr017V2YYDLyn1xF_00ofptWbkg%40mail.gmail.com
pg_wal_replay_wait() is to be used on standby and specifies waiting for
the specific WAL location to be replayed before starting the transaction.
This option is useful when the user makes some data changes on primary and
needs a guarantee to see these changes on standby.
The queue of waiters is stored in the shared memory array sorted by LSN.
During replay of WAL waiters whose LSNs are already replayed are deleted from
the shared memory array and woken up by setting of their latches.
pg_wal_replay_wait() needs to wait without any snapshot held. Otherwise,
the snapshot could prevent the replay of WAL records implying a kind of
self-deadlock. This is why it is only possible to implement
pg_wal_replay_wait() as a procedure working in a non-atomic context,
not a function.
Catversion is bumped.
Discussion: https://postgr.es/m/eb12f9b03851bb2583adab5df9579b4b%40postgrespro.ru
Author: Kartyshov Ivan, Alexander Korotkov
Reviewed-by: Michael Paquier, Peter Eisentraut, Dilip Kumar, Amit Kapila
Reviewed-by: Alexander Lakhin, Bharath Rupireddy, Euler Taveira
If temp tables have dependencies (such as sequences) then it's
possible for autovacuum's cleanup of orphan temp tables to deadlock
against an incoming backend that's trying to clean out the temp
namespace for its own use. That can happen because RemoveTempRelations'
performDeletion call can visit objects within the namespace in
an order different from the order in which a per-table deletion
will visit them.
To fix, observe that performDeletion will begin by taking an exclusive
lock on the temp namespace (even though it won't actually delete it).
So, if we can get a shared lock on the namespace, we can be sure we're
not running concurrently with RemoveTempRelations, while also not
conflicting with ordinary use of the namespace. This requires
introducing a conditional version of LockDatabaseObject, but that's no
big deal. (It's surprising we've got along without that this long.)
Report and patch by Mikhail Zhilin. Back-patch to all supported
branches.
Discussion: https://postgr.es/m/c43ce028-2bc2-4865-9b89-3f706246eed5@postgrespro.ru
Introduce an abstraction allowing relation data to be accessed as a
stream of buffers, with an implementation that is more efficient than
the equivalent sequence of ReadBuffer() calls.
Client code supplies a callback that can say which block number it wants
next, and then consumes individual buffers one at a time from the
stream. This division puts read_stream.c in control of how far ahead it
can see and allows it to read clusters of neighboring blocks with
StartReadBuffers(). It also issues POSIX_FADV_WILLNEED advice ahead of
time when random access is detected.
Other variants of I/O stream will be proposed in future work (for
example to support recovery, whose LsnReadQueue device in
xlogprefetcher.c is a distant cousin of this code and should eventually
be replaced by this), but this basic API is sufficient for many common
executor usage patterns involving predictable access to a single fork of
a single relation.
Several patches using this API are proposed separately.
This stream concept is loosely based on ideas from Andres Freund on how
we should pave the way for later work on asynchronous I/O.
Author: Thomas Munro <thomas.munro@gmail.com>
Author: Heikki Linnakangas <hlinnaka@iki.fi> (contributions)
Author: Melanie Plageman <melanieplageman@gmail.com> (contributions)
Suggested-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-by: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Nazir Bilal Yavuz <byavuz81@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Tested-by: Tomas Vondra <tomas.vondra@enterprisedb.com>
Discussion: https://postgr.es/m/CA+hUKGJkOiOCa+mag4BF+zHo7qo=o9CFheB8=g6uT5TUm2gkvA@mail.gmail.com
Break ReadBuffer() up into two steps. StartReadBuffers() and
WaitReadBuffers() give us two main advantages:
1. Multiple consecutive blocks can be read with one system call.
2. Advice (hints of future reads) can optionally be issued to the
kernel ahead of time.
The traditional ReadBuffer() function is now implemented in terms of
those functions, to avoid duplication.
A new GUC io_combine_limit is defined, and the functions for limiting
per-backend pin counts are made into public APIs. Those are provided
for use by callers of StartReadBuffers(), when deciding how many buffers
to read at once. The following commit will add a higher level mechanism
for doing that automatically with a practical interface.
With some more infrastructure in later work, StartReadBuffers() could
be extended to start real asynchronous I/O instead of just issuing
advice and leaving WaitReadBuffers() to do the work synchronously.
Author: Thomas Munro <thomas.munro@gmail.com>
Author: Andres Freund <andres@anarazel.de> (some optimization tweaks)
Reviewed-by: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-by: Nazir Bilal Yavuz <byavuz81@gmail.com>
Reviewed-by: Dilip Kumar <dilipbalaut@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Tested-by: Tomas Vondra <tomas.vondra@enterprisedb.com>
Discussion: https://postgr.es/m/CA+hUKGJkOiOCa+mag4BF+zHo7qo=o9CFheB8=g6uT5TUm2gkvA@mail.gmail.com
Previously, we used a simple array for storing dead tuple IDs during
lazy vacuum, which had a number of problems:
* The array used a single allocation and so was limited to 1GB.
* The allocation was pessimistically sized according to table size.
* Lookup with binary search was slow because of poor CPU cache and
branch prediction behavior.
This commit replaces that array with the TID store from commit
30e144287a.
Since the backing radix tree makes small allocations as needed, the
1GB limit is now gone. Further, the total memory used is now often
smaller by an order of magnitude or more, depending on the
distribution of blocks and offsets. These two features should make
multiple rounds of heap scanning and index cleanup an extremely rare
event. TID lookup during index cleanup is also several times faster,
even more so when index order is correlated with heap tuple order.
Since there is no longer a predictable relationship between the number
of dead tuples vacuumed and the space taken up by their TIDs, the
number of tuples no longer provides any meaningful insights for users,
nor is the maximum number predictable. For that reason this commit
also changes to byte-based progress reporting, with the relevant
columns of pg_stat_progress_vacuum renamed accordingly to
max_dead_tuple_bytes and dead_tuple_bytes.
For parallel vacuum, both the TID store and supplemental information
specific to vacuum are shared among the parallel vacuum workers. As
with the previous array, we don't take any locks on TidStore during
parallel vacuum since writes are still only done by the leader
process.
Bump catalog version.
Reviewed-by: John Naylor, (in an earlier version) Dilip Kumar
Discussion: https://postgr.es/m/CAD21AoAfOZvmfR0j8VmZorZjL7RhTiQdVttNuC4W-Shdc2a-AA%40mail.gmail.com
This way, we can fold the list of lock names to occur in
BuiltinTrancheNames instead of having its own separate array. This
saves two lines of code in GetLWTrancheName and some space in
BuiltinTrancheNames, as foreseen in commit 74a7306310, as well as
removing the need for a separate lwlocknames.c file.
We still have to build lwlocknames.h using Perl code, which initially I
wanted to avoid, but it gives us the chance to cross-check
wait_event_names.txt.
Discussion: https://postgr.es/m/202401231025.gbv4nnte5fmm@alvherre.pgsql
We don't determine the position at which a process waiting for a lock
should insert itself into the wait queue until we reach ProcSleep(),
and we may at that point discover that we must insert ourselves ahead
of everyone who wants a conflicting lock, in which case we obtain the
lock immediately. Up until now, a no-wait lock acquisition would fail
in such cases, erroneously claiming that the lock couldn't be obtained
immediately. Fix that by trying ProcSleep even in the no-wait case.
No back-patch for now, because I'm treating this as an improvement to
the existing no-wait feature. It could instead be argued that it's a
bug fix, on the theory that there should never be any case whatsoever
where no-wait fails to obtain a lock that would have been obtained
immediately without no-wait, but I'm reluctant to interpret the
semantics of no-wait that strictly.
Robert Haas and Jingxian Li
Discussion: http://postgr.es/m/CA+TgmobCH-kMXGVpb0BB-iNMdtcNkTvcZ4JBxDJows3kYM+GDg@mail.gmail.com
Currently, pg_visibility computes its xid horizon using the
GetOldestNonRemovableTransactionId(). The problem is that this horizon can
sometimes go backward. That can lead to reporting false errors.
In order to fix that, this commit implements a new function
GetStrictOldestNonRemovableTransactionId(). This function computes the xid
horizon, which would be guaranteed to be newer or equal to any xid horizon
computed before.
We have to do the following to achieve this.
1. Ignore processes xmin's, because they consider connection to other databases
that were ignored before.
2. Ignore KnownAssignedXids, because they are not database-aware. At the same
time, the primary could compute its horizons database-aware.
3. Ignore walsender xmin, because it could go backward if some replication
connections don't use replication slots.
As a result, we're using only currently running xids to compute the horizon.
Surely these would significantly sacrifice accuracy. But we have to do so to
avoid reporting false errors.
Inspired by earlier patch by Daniel Shelepanov and the following discussion
with Robert Haas and Tom Lane.
Discussion: https://postgr.es/m/1649062270.289865713%40f403.i.mail.ru
Reviewed-by: Alexander Lakhin, Dmitry Koval
With commit 21d9c3ee4e, SMgrRelations remain valid until end of
transaction (or longer if they're "pinned"). Relcache invalidation can
happen in the middle of a transaction, so we must not destroy them at
relcache invalidation anymore.
This was revealed by failures in the 'constraints' test in buildfarm
animals using -DCLOBBER_CACHE_ALWAYS. That started failing with commit
8af2565248, which was the first commit that started to rely on an
SMgrRelation living until end of transaction.
Diagnosed-by: Tomas Vondra, Thomas Munro
Reviewed-by: Thomas Munro
Discussion: https://www.postgresql.org/message-id/CA%2BhUKGK%2B5DOmLaBp3Z7C4S-Yv6yoROvr1UncjH2S1ZbPT8D%2BZg%40mail.gmail.com
The adminpack extension was only used to support pgAdmin III, which
in turn was declared EOL many years ago. Removing the extension also
allows us to remove functions from core as well which were only used
to support old version of adminpack.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Nathan Bossart <nathandbossart@gmail.com>
Reviewed-by: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Discussion: https://postgr.es/m/CALj2ACUmL5TraYBUBqDZBi1C+Re8_=SekqGYqYprj_W8wygQ8w@mail.gmail.com
as determined by include-what-you-use (IWYU)
While IWYU also suggests to *add* a bunch of #include's (which is its
main purpose), this patch does not do that. In some cases, a more
specific #include replaces another less specific one.
Some manual adjustments of the automatic result:
- IWYU currently doesn't know about includes that provide global
variable declarations (like -Wmissing-variable-declarations), so
those includes are being kept manually.
- All includes for port(ability) headers are being kept for now, to
play it safe.
- No changes of catalog/pg_foo.h to catalog/pg_foo_d.h, to keep the
patch from exploding in size.
Note that this patch touches just *.c files, so nothing declared in
header files changes in hidden ways.
As a small example, in src/backend/access/transam/rmgr.c, some IWYU
pragma annotations are added to handle a special case there.
Discussion: https://www.postgresql.org/message-id/flat/af837490-6b2f-46df-ba05-37ea6a6653fc%40eisentraut.org
Remove IsBackgroundWorker, IsAutoVacuumLauncherProcess(),
IsAutoVacuumWorkerProcess(), and IsLogicalSlotSyncWorker() in favor of
new Am*Process() macros that use MyBackendType. For consistency with
the existing Am*Process() macros.
Reviewed-by: Andres Freund
Discussion: https://www.postgresql.org/message-id/f3ecd4cb-85ee-4e54-8278-5fabfb3a4ed0@iki.fi
Now that BackendId was just another index into the proc array, it was
redundant with the 0-based proc numbers used in other places. Replace
all usage of backend IDs with proc numbers.
The only place where the term "backend id" remains is in a few pgstat
functions that expose backend IDs at the SQL level. Those IDs are now
in fact 0-based ProcNumbers too, but the documentation still calls
them "backend ids". That term still seems appropriate to describe what
the numbers are, so I let it be.
One user-visible effect is that pg_temp_0 is now a valid temp schema
name, for backend with ProcNumber 0.
Reviewed-by: Andres Freund
Discussion: https://www.postgresql.org/message-id/8171f1aa-496f-46a6-afc3-c46fe7a9b407@iki.fi
Previously, backend ID was an index into the ProcState array, in the
shared cache invalidation manager (sinvaladt.c). The entry in the
ProcState array was reserved at backend startup by scanning the array
for a free entry, and that was also when the backend got its backend
ID. Things become slightly simpler if we redefine backend ID to be the
index into the PGPROC array, and directly use it also as an index to
the ProcState array. This uses a little more memory, as we reserve a
few extra slots in the ProcState array for aux processes that don't
need them, but the simplicity is worth it.
Aux processes now also have a backend ID. This simplifies the
reservation of BackendStatusArray and ProcSignal slots.
You can now convert a backend ID into an index into the PGPROC array
simply by subtracting 1. We still use 0-based "pgprocnos" in various
places, for indexes into the PGPROC array, but the only difference now
is that backend IDs start at 1 while pgprocnos start at 0. (The next
commmit will get rid of the term "backend ID" altogether and make
everything 0-based.)
There is still a 'backendId' field in PGPROC, now part of 'vxid' which
encapsulates the backend ID and local transaction ID together. It's
needed for prepared xacts. For regular backends, the backendId is
always equal to pgprocno + 1, but for prepared xact PGPROC entries,
it's the ID of the original backend that processed the transaction.
Reviewed-by: Andres Freund, Reid Thompson
Discussion: https://www.postgresql.org/message-id/8171f1aa-496f-46a6-afc3-c46fe7a9b407@iki.fi
In the past, FileRead() and FileWrite() used types based on the Unix
read() and write() functions from before C and POSIX standardization,
though not exactly (we had int for amount instead of unsigned). In
commit 2d4f1ba6 we changed to the appropriate standard C types, just
like the modern POSIX functions they wrap, but again not exactly: the
return type stayed as int. In theory, a ssize_t value could be returned
by the underlying call that is too large for an int.
That wasn't really a live bug, because we don't expect PostgreSQL code
to perform reads or writes of gigabytes, and OSes probably apply
internal caps smaller than that anyway. This change is done on the
principle that the return might as well follow the standard interfaces
consistently.
Reported-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Discussion: https://postgr.es/m/1672202.1703441340%40sss.pgh.pa.us
More precisely, what we do here is make the SLRU cache sizes
configurable with new GUCs, so that sites with high concurrency and big
ranges of transactions in flight (resp. multixacts/subtransactions) can
benefit from bigger caches. In order for this to work with good
performance, two additional changes are made:
1. the cache is divided in "banks" (to borrow terminology from CPU
caches), and algorithms such as eviction buffer search only affect
one specific bank. This forestalls the problem that linear searching
for a specific buffer across the whole cache takes too long: we only
have to search the specific bank, whose size is small. This work is
authored by Andrey Borodin.
2. Change the locking regime for the SLRU banks, so that each bank uses
a separate LWLock. This allows for increased scalability. This work
is authored by Dilip Kumar. (A part of this was previously committed as
d172b717c6f4.)
Special care is taken so that the algorithms that can potentially
traverse more than one bank release one bank's lock before acquiring the
next. This should happen rarely, but particularly clog.c's group commit
feature needed code adjustment to cope with this. I (Álvaro) also added
lots of comments to make sure the design is sound.
The new GUCs match the names introduced by bcdfa5f2e2 in the
pg_stat_slru view.
The default values for these parameters are similar to the previous
sizes of each SLRU. commit_ts, clog and subtrans accept value 0, which
means to adjust by dividing shared_buffers by 512 (so 2MB for every 1GB
of shared_buffers), with a cap of 8MB. (A new slru.c function
SimpleLruAutotuneBuffers() was added to support this.) The cap was
previously 1MB for clog, so for sites with more than 512MB of shared
memory the total memory used increases, which is likely a good tradeoff.
However, other SLRUs (notably multixact ones) retain smaller sizes and
don't support a configured value of 0. These values based on
shared_buffers may need to be revisited, but that's an easy change.
There was some resistance to adding these new GUCs: it would be better
to adjust to memory pressure automatically somehow, for example by
stealing memory from shared_buffers (where the caches can grow and
shrink naturally). However, doing that seems to be a much larger
project and one which has made virtually no progress in several years,
and because this is such a pain point for so many users, here we take
the pragmatic approach.
Author: Andrey Borodin <x4mmm@yandex-team.ru>
Author: Dilip Kumar <dilipbalaut@gmail.com>
Reviewed-by: Amul Sul, Gilles Darold, Anastasia Lubennikova,
Ivan Lazarev, Robert Haas, Thomas Munro, Tomas Vondra,
Yura Sokolov, Васильев Дмитрий (Dmitry Vasiliev).
Discussion: https://postgr.es/m/2BEC2B3F-9B61-4C1D-9FB5-5FAB0F05EF86@yandex-team.ru
Discussion: https://postgr.es/m/CAFiTN-vzDvNz=ExGXz6gdyjtzGixKSqs0mKHMmaQ8sOSEFZ33A@mail.gmail.com
The new names are intended to match those in an upcoming patch that adds
a few GUCs to configure the SLRU buffer sizes.
Backwards compatibility concern: this changes the accepted names for
function pg_stat_slru_rest(). Since this function recognizes "any other
string" as a request to reset the entry for "other", this means that
calling it with the old names would silently reset "other" instead of
doing nothing or throwing an error.
Reviewed-by: Andrey M. Borodin <x4mmm@yandex-team.ru>
Discussion: https://postgr.es/m/202402261616.dlriae7b6emv@alvherre.pgsql
Presently, string keys are not well-supported for dshash tables.
The dshash code always copies key_size bytes into new entries'
keys, and dshash.h only provides compare and hash functions that
forward to memcmp() and tag_hash(), both of which do not stop at
the first NUL. This means that callers must pad string keys so
that the data beyond the first NUL does not adversely affect the
results of copying, comparing, and hashing the keys.
To better support string keys in dshash tables, this commit does
a couple things:
* A new copy_function field is added to the dshash_parameters
struct. This function pointer specifies how the key should be
copied into new table entries. For example, we only want to copy
up to the first NUL byte for string keys. A dshash_memcpy()
helper function is provided and used for all existing in-tree
dshash tables without string keys.
* A set of helper functions for string keys are provided. These
helper functions forward to strcmp(), strcpy(), and
string_hash(), all of which ignore data beyond the first NUL.
This commit also adjusts the DSM registry's dshash table to use the
new helper functions for string keys.
Reviewed-by: Andy Fan
Discussion: https://postgr.es/m/20240119215941.GA1322079%40nathanxps13
The new facility makes it easier to optimize bulk loading, as the
logic for buffering, WAL-logging, and syncing the relation only needs
to be implemented once. It's also less error-prone: We have had a
number of bugs in how a relation is fsync'd - or not - at the end of a
bulk loading operation. By centralizing that logic to one place, we
only need to write it correctly once.
The new facility is faster for small relations: Instead of of calling
smgrimmedsync(), we register the fsync to happen at next checkpoint,
which avoids the fsync latency. That can make a big difference if you
are e.g. restoring a schema-only dump with lots of relations.
It is also slightly more efficient with large relations, as the WAL
logging is performed multiple pages at a time. That avoids some WAL
header overhead. The sorted GiST index build did that already, this
moves the buffering to the new facility.
The changes to pageinspect GiST test needs an explanation: Before this
patch, the sorted GiST index build set the LSN on every page to the
special GistBuildLSN value, not the LSN of the WAL record, even though
they were WAL-logged. There was no particular need for it, it just
happened naturally when we wrote out the pages before WAL-logging
them. Now we WAL-log the pages first, like in B-tree build, so the
pages are stamped with the record's real LSN. When the build is not
WAL-logged, we still use GistBuildLSN. To make the test output
predictable, use an unlogged index.
Reviewed-by: Andres Freund
Discussion: https://www.postgresql.org/message-id/30e8f366-58b3-b239-c521-422122dd5150%40iki.fi
By enabling slot synchronization, all the failover logical replication
slots on the primary (assuming configurations are appropriate) are
automatically created on the physical standbys and are synced
periodically. The slot sync worker on the standby server pings the primary
server at regular intervals to get the necessary failover logical slots
information and create/update the slots locally. The slots that no longer
require synchronization are automatically dropped by the worker.
The nap time of the worker is tuned according to the activity on the
primary. The slot sync worker waits for some time before the next
synchronization, with the duration varying based on whether any slots were
updated during the last cycle.
A new parameter sync_replication_slots enables or disables this new
process.
On promotion, the slot sync worker is shut down by the startup process to
drop any temporary slots acquired by the slot sync worker and to prevent
the worker from trying to fetch the failover slots.
A functionality to allow logical walsenders to wait for the physical will
be done in a subsequent commit.
Author: Shveta Malik, Hou Zhijie based on design inputs by Masahiko Sawada and Amit Kapila
Reviewed-by: Masahiko Sawada, Bertrand Drouvot, Peter Smith, Dilip Kumar, Ajin Cherian, Nisha Moond, Kuroda Hayato, Amit Kapila
Discussion: https://postgr.es/m/514f6f2f-6833-4539-39f1-96cd1e011f23@enterprisedb.com
This commit adds timeout that is expected to be used as a prevention
of long-running queries. Any session within the transaction will be
terminated after spanning longer than this timeout.
However, this timeout is not applied to prepared transactions.
Only transactions with user connections are affected.
Discussion: https://postgr.es/m/CAAhFRxiQsRs2Eq5kCo9nXE3HTugsAAJdSQSmxncivebAxdmBjQ%40mail.gmail.com
Author: Andrey Borodin <amborodin@acm.org>
Author: Japin Li <japinli@hotmail.com>
Author: Junwang Zhao <zhjwpku@gmail.com>
Reviewed-by: Nikolay Samokhvalov <samokhvalov@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Fujii Masao <masao.fujii@oss.nttdata.com>
Reviewed-by: bt23nguyent <bt23nguyent@oss.nttdata.com>
Reviewed-by: Yuhang Qiu <iamqyh@gmail.com>
Presently, we rely on each individual signal handler to save the
initial value of errno and then restore it before returning if
needed. This is easily forgotten and, if missed, often goes
undetected for a long time.
In commit 3b00fdba9f, we introduced a wrapper signal handler
function that checks whether MyProcPid matches getpid(). This
commit moves the aforementioned errno restoration code from the
individual signal handlers to the new wrapper handler so that we no
longer need to worry about missing it.
Reviewed-by: Andres Freund, Noah Misch
Discussion: https://postgr.es/m/20231121212008.GA3742740%40nathanxps13
This commit introduces a new SQL function pg_sync_replication_slots()
which is used to synchronize the logical replication slots from the
primary server to the physical standby so that logical replication can be
resumed after a failover or planned switchover.
A new 'synced' flag is introduced in pg_replication_slots view, indicating
whether the slot has been synchronized from the primary server. On a
standby, synced slots cannot be dropped or consumed, and any attempt to
perform logical decoding on them will result in an error.
The logical replication slots on the primary can be synchronized to the
hot standby by using the 'failover' parameter of
pg-create-logical-replication-slot(), or by using the 'failover' option of
CREATE SUBSCRIPTION during slot creation, and then calling
pg_sync_replication_slots() on standby. For the synchronization to work,
it is mandatory to have a physical replication slot between the primary
and the standby aka 'primary_slot_name' should be configured on the
standby, and 'hot_standby_feedback' must be enabled on the standby. It is
also necessary to specify a valid 'dbname' in the 'primary_conninfo'.
If a logical slot is invalidated on the primary, then that slot on the
standby is also invalidated.
If a logical slot on the primary is valid but is invalidated on the
standby, then that slot is dropped but will be recreated on the standby in
the next pg_sync_replication_slots() call provided the slot still exists
on the primary server. It is okay to recreate such slots as long as these
are not consumable on standby (which is the case currently). This
situation may occur due to the following reasons:
- The 'max_slot_wal_keep_size' on the standby is insufficient to retain
WAL records from the restart_lsn of the slot.
- 'primary_slot_name' is temporarily reset to null and the physical slot
is removed.
The slot synchronization status on the standby can be monitored using the
'synced' column of pg_replication_slots view.
A functionality to automatically synchronize slots by a background worker
and allow logical walsenders to wait for the physical will be done in
subsequent commits.
Author: Hou Zhijie, Shveta Malik, Ajin Cherian based on an earlier version by Peter Eisentraut
Reviewed-by: Masahiko Sawada, Bertrand Drouvot, Peter Smith, Dilip Kumar, Nisha Moond, Kuroda Hayato, Amit Kapila
Discussion: https://postgr.es/m/514f6f2f-6833-4539-39f1-96cd1e011f23@enterprisedb.com
Michael Paquier
Peter Eisentraut
Noah Misch
David Rowley
Daniel Gustafsson
Andres Freund
Alexander Korotkov
Masahiko Sawada
Thomas Munro
Heikki Linnakangas
Alvaro Herrera
Tom Lane
Robert Haas
Nathan Bossart
Amit Kapila