Cumulative stats kinds gain the capability to write additional per-entry
data when flushing the stats at shutdown, and read this data when
loading back the stats at startup. This can be fit for example in the
case of variable-length data (like normalized query strings), so as it
becomes possible to link the shared memory stats entries to data that is
stored in a different area, like a DSA segment.
Three new optional callbacks are added to PgStat_KindInfo, available to
variable-numbered stats kinds:
* to_serialized_data: writes auxiliary data for an entry.
* from_serialized_data: reads auxiliary data for an entry.
* finish: performs actions after read/write/discard operations. This is
invoked after processing all the entries of a kind, allowing extensions
to close file handles and clean up resources.
Stats kinds have the option to store this data in the existing pgstats
file, but can as well store it in one or more additional files whose
names can be built upon the entry keys. The new serialized callbacks
are called once an entry key is read or written from the main stats
file. A file descriptor to the main pgstats file is available in the
arguments of the callbacks.
Author: Sami Imseih <samimseih@gmail.com>
Co-authored-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/CAA5RZ0s9SDOu+Z6veoJCHWk+kDeTktAtC-KY9fQ9Z6BJdDUirQ@mail.gmail.com
The current list from the buildfarm includes quite a few typedef
names that it used to miss. The reason is a bit obscure, but it
seems likely to have something to do with our recent increased
use of palloc_object and palloc_array. In any case, this makes
the relevant struct declarations be much more nicely formatted,
so I'll take it. Install the current list and re-run pgindent
to update affected code.
Syncing with the current list also removes some obsolete
typedef names and fixes some alphabetization errors.
Discussion: https://postgr.es/m/1681301.1765742268@sss.pgh.pa.us
There doesn't seem to be any great reason why this has been a macro
rather than a typedef. But doing it like that means our buildfarm
typedef tooling doesn't capture the name as a typedef. That would
result in pgindent glitches, except that we've seemingly kept it
in typedefs.list manually. That's obviously error-prone, so let's
convert it to a typedef now.
Discussion: https://postgr.es/m/1681301.1765742268@sss.pgh.pa.us
Change WAIT_LSN_TYPE_COUNT from an enum sentinel to a macro definition,
in a similar way to IOObject, IOContext, and BackendType enums. Remove
explicit enum value assignments well.
Author: Xuneng Zhou <xunengzhou@gmail.com>
Previously, c.h made <assert.h> only available in frontends (#ifdef
FRONTEND), which was probably reasonable, because the only thing it
would give you is assert(), which you generally shouldn't use in the
backend. But with C11, <assert.h> also makes available
static_assert(), which would be useful everywhere. So this patch
moves <assert.h> to the commonly available header files in c.h and
fixes a small complication in regcustom.h that resulted from that.
Co-authored-by: Thomas Munro <thomas.munro@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CA%2BhUKGKvr0x_oGmQTUkx%3DODgSksT2EtgCA6LmGx_jQFG%3DsDUpg%40mail.gmail.com
Although clang claims to be compatible with gcc's printf format
archetypes, this appears to be a falsehood: it likes __syslog__
(which gcc does not, on most platforms) and doesn't accept
gnu_printf. This means that if you try to use gcc with clang++
or clang with g++, you get compiler warnings when compiling
printf-like calls in our C++ code. This has been true for quite
awhile, but it's gotten more annoying with the recent appearance
of several buildfarm members that are configured like this.
To fix, run separate probes for the format archetype to use with the
C and C++ compilers, and conditionally define PG_PRINTF_ATTRIBUTE
depending on __cplusplus.
(We could alternatively insist that you not mix-and-match C and
C++ compilers; but if the case works otherwise, this is a poor
reason to insist on that.)
No back-patch for now, but we may want to do that if this
patch survives buildfarm testing.
Discussion: https://postgr.es/m/986485.1764825548@sss.pgh.pa.us
PostgreSQL's src/port/open.c has always set bInheritHandle = TRUE
when opening files on Windows, making all file descriptors inheritable
by child processes. This meant the O_CLOEXEC flag, added to many call
sites by commit 1da569ca1f (v16), was silently ignored.
The original commit included a comment suggesting that our open()
replacement doesn't create inheritable handles, but it was a mis-
understanding of the code path. In practice, the code was creating
inheritable handles in all cases.
This hasn't caused widespread problems because most child processes
(archive_command, COPY PROGRAM, etc.) operate on file paths passed as
arguments rather than inherited file descriptors. Even if a child
wanted to use an inherited handle, it would need to learn the numeric
handle value, which isn't passed through our IPC mechanisms.
Nonetheless, the current behavior is wrong. It violates documented
O_CLOEXEC semantics, contradicts our own code comments, and makes
PostgreSQL behave differently on Windows than on Unix. It also creates
potential issues with future code or security auditing tools.
To fix, define O_CLOEXEC to _O_NOINHERIT in master, previously used by
O_DSYNC. We use different values in the back branches to preserve
existing values. In pgwin32_open_handle() we set bInheritHandle
according to whether O_CLOEXEC is specified, for the same atomic
semantics as POSIX in multi-threaded programs that create processes.
Backpatch-through: 16
Author: Bryan Green <dbryan.green@gmail.com>
Co-authored-by: Thomas Munro <thomas.munro@gmail.com> (minor adjustments)
Discussion: https://postgr.es/m/e2b16375-7430-4053-bda3-5d2194ff1880%40gmail.com
POSIX has for a long time defined the "j" length modifier for
printf conversions as meaning the size of intmax_t or uintmax_t.
We got away without supporting that so far, because we were not
using intmax_t anywhere. However, commit e6be84356 re-introduced
upstream's use of intmax_t and PRIdMAX into zic.c. It emerges
that on some platforms (at least FreeBSD and macOS), <inttypes.h>
defines PRIdMAX as "jd", so that snprintf.c falls over if that is
used. (We hadn't noticed yet because it would only be apparent
if bad data is fed to zic, resulting in an error report, and even
then the only visible symptom is a missing line number in the
error message.)
We could revert that decision from our copy of zic.c, but
on the whole it seems better to update snprintf.c to support
this standard modifier. There might well be extensions,
now or in future, that expect it to work.
I did this in the lazy man's way of translating "j" to either
"l" or "ll" depending on a compile-time sizeof() check, just
as was done long ago to support "z" for size_t. One could
imagine promoting intmax_t to have full support in snprintf.c,
for example converting fmtint()'s value argument and internal
arithmetic to use [u]intmax_t not [unsigned] long long. But
that'd be more work and I'm hesitant to do it anyway: if there
are any platforms out there where intmax_t is actually wider
than "long long", this would doubtless result in a noticeable
speed penalty to snprintf(). Let's not go there until we have
positive evidence that there's a reason to, and some way to
measure what size of penalty we're taking.
Author: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/3210703.1765236740@sss.pgh.pa.us
This eliminates MultiXactOffset wraparound and the 2^32 limit on the
total number of multixid members. Multixids are still limited to 2^31,
but this is a nice improvement because 'members' can grow much faster
than the number of multixids. On such systems, you can now run longer
before hitting hard limits or triggering anti-wraparound vacuums.
Not having to deal with MultiXactOffset wraparound also simplifies the
code and removes some gnarly corner cases.
We no longer need to perform emergency anti-wraparound freezing
because of running out of 'members' space, so the offset stop limit is
gone. But you might still not want 'members' to consume huge amounts
of disk space. For that reason, I kept the logic for lowering vacuum's
multixid freezing cutoff if a large amount of 'members' space is
used. The thresholds for that are roughly the same as the "safe" and
"danger" thresholds used before, 2 billion transactions and 4 billion
transactions. This keeps the behavior for the freeze cutoff roughly
the same as before. It might make sense to make this smarter or
configurable, now that the threshold is only needed to manage disk
usage, but that's left for the future.
Add code to pg_upgrade to convert multitransactions from the old to
the new format, rewriting the pg_multixact SLRU files. Because
pg_upgrade now rewrites the files, we can get rid of some hacks we had
put in place to deal with old bugs and upgraded clusters. Bump catalog
version for the pg_multixact/offsets format change.
Author: Maxim Orlov <orlovmg@gmail.com>
Reviewed-by: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Reviewed-by: Alexander Korotkov <aekorotkov@gmail.com>
Reviewed-by: wenhui qiu <qiuwenhuifx@gmail.com>
Discussion: https://www.postgresql.org/message-id/CACG%3DezaWg7_nt-8ey4aKv2w9LcuLthHknwCawmBgEeTnJrJTcw@mail.gmail.com
The idea is to encourage more the use of these new routines across the
tree, as these offer stronger type safety guarantees than palloc().
The following paths are included in this batch, treating all the areas
proposed by the author for the most trivial changes, except src/backend
(by far the largest batch):
src/bin/
src/common/
src/fe_utils/
src/include/
src/pl/
src/test/
src/tutorial/
Similar work has been done in 31d3847a37.
The code compiles the same before and after this commit, with the
following exceptions due to changes in line numbers because some of the
new allocation formulas are shorter:
blkreftable.c
pgfnames.c
pl_exec.c
Author: David Geier <geidav.pg@gmail.com>
Discussion: https://postgr.es/m/ad0748d4-3080-436e-b0bc-ac8f86a3466a@gmail.com
Quite a bit of code within nbtutils.c is only called by _bt_readpage.
Move _bt_readpage and all of the nbtutils.c functions it depends on into
a new .c file, nbtreadpage.c. Also reorder some of the functions within
the new file for clarity.
This commit has no functional impact. It is strictly mechanical.
Author: Peter Geoghegan <pg@bowt.ie>
Reviewed-By: Victor Yegorov <vyegorov@gmail.com>
Discussion: https://postgr.es/m/CAH2-WzmwMwcwKFgaf+mYPwiz3iL4AqpXnwtW_O0vqpWPXRom9Q@mail.gmail.com
Instead of passing "JsonbParseState **" to pushJsonbValue(),
pass a pointer to a JsonbInState, which will contain the
parseState stack pointer as well as other useful fields.
Also, instead of returning a JsonbValue pointer that is often
meaningless/ignored, return the top-level JsonbValue pointer
in the "result" field of the JsonbInState.
This involves a lot of (mostly mechanical) edits, but I think
the results are notationally cleaner and easier to understand.
Certainly the business with sometimes capturing the result of
pushJsonbValue() and sometimes not was bug-prone and incapable of
mechanical verification. In the new arrangement, JsonbInState.result
remains null until we've completed a valid sequence of pushes, so
that an incorrect sequence will result in a null-pointer dereference,
not mistaken use of a partial result.
However, this isn't simply an exercise in prettier notation.
The real reason for doing it is to provide a mechanism whereby
pushJsonbValue() can be told to construct the JsonbValue tree
in a context that is not CurrentMemoryContext. That happens
when a non-null "outcontext" is specified in the JsonbInState.
No callers exercise that option in this patch, but the next
patch in the series will make use of it.
I tried to improve the comments in this area too.
Author: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: jian he <jian.universality@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/1060917.1753202222@sss.pgh.pa.us
pg_type.typlen says 12 for the size of timetz, but sizeof(TimeTzADT)
will be 16 on most platforms due to alignment padding. Using the
sizeof number is no problem for usages such as palloc'ing a result
datum, but in usages such as datumCopy we really ought to match
what pg_type says. Add a macro TIMETZ_TYPLEN so that we have a
symbolic way to write that rather than hard-coding "12".
I cannot find any place where we've needed this so far, but an
upcoming patch requires it.
Author: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/2329959.1765047648@sss.pgh.pa.us
The SQL standard says that corr() and friends should return NULL in
the mathematically-undefined case where all the inputs in one of
the columns have the same value. We were checking that by seeing
if the sums Sxx and Syy were zero, but that approach is very
vulnerable to roundoff error: if a sum is close to zero but not
exactly that, we'd come out with a pretty silly non-NULL result.
Instead, directly track whether the inputs are all equal by
remembering the common value in each column. Once we detect
that a new input is different from before, represent that by
storing NaN for the common value. (An objection to this scheme
is that if the inputs are all NaN, we will consider that they
were not all equal. But under IEEE float arithmetic rules,
one NaN is never equal to another, so this behavior is arguably
correct. Moreover it matches what we did before in such cases.)
Then, leave the sums at their exact value of zero for as long
as we haven't detected different input values.
This solution requires the aggregate transition state to contain
8 float values not 6, which is not problematic, and it seems to add
less than 1% to the aggregates' runtime, which seems acceptable.
While we're here, improve corr()'s final function to cope with
overflow/underflow in the final calculation, and to clamp its
result to [-1, 1] in case of roundoff error.
Although this is arguably a bug fix, it requires a catversion bump
due to the change in aggregates' initial states, so it can't be
back-patched.
Patch written by me, but many of the ideas are due to Dean Rasheed,
who also did a deal of testing.
Bug: #19340
Reported-by: Oleg Ivanov <o15611@gmail.com>
Author: Tom Lane <tgl@sss.pgh.pa.us>
Co-authored-by: Dean Rasheed <dean.a.rasheed@gmail.com>
Discussion: https://postgr.es/m/19340-6fb9f6637f562092@postgresql.org
Commit 76b78721ca introduced two new columns in pg_stat_replication_slots
to improve monitoring of slot synchronization. One of these columns was
named slotsync_skip_at, which is inconsistent with the naming convention
used for similar columns in other system views.
Columns that store timestamps of the most recent event typically use the
'last_' in the column name (e.g., last_autovacuum, checksum_last_failure).
Renaming slotsync_skip_at to slotsync_last_skip aligns with this pattern,
making the purpose of the column clearer and improving overall consistency
across the views.
Author: Shlok Kyal <shlok.kyal.oss@gmail.com>
Reviewed-by: Michael Banck <mbanck@gmx.net>
Discussion: https://postgr.es/m/20251128091552.GB13635@p46.dedyn.io;lightning.p46.dedyn.io
Discussion: https://postgr.es/m/CAE9k0PkhfKrTEAsGz4DjOhEj1nQ+hbQVfvWUxNacD38ibW3a1g@mail.gmail.com
In an upcoming patch more wait events will be added to the wait event
class (for buffer locking), making the current name too
specific. Alternatively we could introduce a dedicated wait event class for
those, but it seems somewhat confusing to have a BUFFERPIN and a BUFFER wait
event class.
Reviewed-by: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://postgr.es/m/fvfmkr5kk4nyex56ejgxj3uzi63isfxovp2biecb4bspbjrze7@az2pljabhnff
With this commit, the next multixid's offset will always be set on the
offsets page, by the time that a backend might try to read it, so we
no longer need the waiting mechanism with the condition variable. In
other words, this eliminates "corner case 2" mentioned in the
comments.
The waiting mechanism was broken in a few scenarios:
- When nextMulti was advanced without WAL-logging the next
multixid. For example, if a later multixid was already assigned and
WAL-logged before the previous one was WAL-logged, and then the
server crashed. In that case the next offset would never be set in
the offsets SLRU, and a query trying to read it would get stuck
waiting for it. Same thing could happen if pg_resetwal was used to
forcibly advance nextMulti.
- In hot standby mode, a deadlock could happen where one backend waits
for the next multixid assignment record, but WAL replay is not
advancing because of a recovery conflict with the waiting backend.
The old TAP test used carefully placed injection points to exercise
the old waiting code, but now that the waiting code is gone, much of
the old test is no longer relevant. Rewrite the test to reproduce the
IPC/MultixactCreation hang after crash recovery instead, and to verify
that previously recorded multixids stay readable.
Backpatch to all supported versions. In back-branches, we still need
to be able to read WAL that was generated before this fix, so in the
back-branches this includes a hack to initialize the next offsets page
when replaying XLOG_MULTIXACT_CREATE_ID for the last multixid on a
page. On 'master', bump XLOG_PAGE_MAGIC instead to indicate that the
WAL is not compatible.
Author: Andrey Borodin <amborodin@acm.org>
Reviewed-by: Dmitry Yurichev <dsy.075@yandex.ru>
Reviewed-by: Álvaro Herrera <alvherre@kurilemu.de>
Reviewed-by: Kirill Reshke <reshkekirill@gmail.com>
Reviewed-by: Ivan Bykov <i.bykov@modernsys.ru>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://www.postgresql.org/message-id/172e5723-d65f-4eec-b512-14beacb326ce@yandex.ru
Backpatch-through: 14
The comment for the Pointer type said 'XXX Pointer arithmetic is done
with this, so it can't be void * under "true" ANSI compilers.'. This
has been fixed in the previous commit 756a436893. This now changes
the definition of the type from char * to void *, as envisaged by that
comment.
Extension code that relies on using Pointer for pointer arithmetic
will need to make changes similar to commit 756a436893, but those
changes would be backward compatible.
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Reviewed-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Discussion: https://www.postgresql.org/message-id/4154950a-47ae-4223-bd01-1235cc50e933%40eisentraut.org
Presently, this view reports NULL for the size of DSAs and dshash
tables because 1) the current backend might not be attached to them
and 2) the registry doesn't save the pointers to the dsa_area or
dshash_table in local memory. Also, the view doesn't show
partially-initialized entries to avoid ambiguity, since those
entries would report a NULL size as well.
This commit introduces a function that looks up the size of a DSA
given its handle (transiently attaching to the control segment if
needed) and teaches pg_dsm_registry_allocations to use it to show
the size of successfully-initialized DSA and dshash entries.
Furthermore, the view now reports partially-initialized entries
with a NULL size.
Reviewed-by: Rahila Syed <rahilasyed90@gmail.com>
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/aSeEDeznAsHR1_YF%40nathan
This commit updates two functions that convert "timestamptz" to
"timestamp", and vice-versa, to use the soft error reporting rather than
a their own logic to do the same. These are now named as follows:
- timestamp2timestamptz_safe()
- timestamptz2timestamp_safe()
These functions were suffixed with "_opt_overflow", previously.
This shaves some code, as it is possible to detect how a timestamp[tz]
overflowed based on the returned value rather than a custom state. It
is optionally possible for the callers of these functions to rely on the
error generated internally by these functions, depending on the error
context.
Similar work has been done in d03668ea05 and 4246a977ba.
Reviewed-by: Amul Sul <sulamul@gmail.com>
Discussion: https://postgr.es/m/aS09YF2GmVXjAxbJ@paquier.xyz
The regex mechanism scans through the first "max_chr" character values
to cache character property ranges (isalpha, etc.). For single-byte
encodings, there's no sense in scanning beyond UCHAR_MAX; but for
UTF-8 it makes sense to cache higher code point values (though not all
of them; only up to MAX_SIMPLE_CHR).
Prior to 5a38104b36, the logic about how many character values to scan
was based on the pg_regex_strategy, which was dependent on the
provider. Commit 5a38104b36 preserved that logic exactly, allowing
different providers to define the "max_chr".
Now, change it to depend only on the encoding and whether
ctype_is_c. For this specific calculation, distinguishing between
providers creates more complexity than it's worth.
Discussion: https://postgr.es/m/450ceb6260cad30d7afdf155d991a9caafee7c0d.camel@j-davis.com
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
This split exists for most of the other RMGRs, and makes cleaner the
separation between the WAL code, the redo code and the record
description code (already in its own file) when it comes to the sequence
RMGR. The redo and masking routines are moved to a new file,
sequence_xlog.c. All the RMGR routines are now located in a new header,
sequence_xlog.h.
This separation is useful for a different patch related to sequences
that I have been working on, where it makes a refactoring of sequence.c
easier if its RMGR routines and its core routines are split.
Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-by: Kirill Reshke <reshkekirill@gmail.com>
Discussion: https://postgr.es/m/aSfTxIWjiXkTKh1E@paquier.xyz
This commit changes some functions related to the data types date and
timestamp to use the soft error reporting rather than a custom boolean
flag called "overflow", used to let the callers of these functions know
if an overflow happens.
This results in the removal of some boilerplate code, as it is possible
to rely on an error context rather than a custom state, with the
possibility to use the error generated inside the functions updated
here, if necessary.
These functions were suffixed with "_opt_overflow". They are now
renamed to use "_safe" as suffix.
This work is similar to 4246a977ba.
Author: Amul Sul <sulamul@gmail.com>
Reviewed-by: Amit Langote <amitlangote09@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/CAAJ_b95HEmFyzHZfsdPquSHeswcopk8MCG1Q_vn4tVkZ+xxofw@mail.gmail.com
There was a pg_isblank() function that claimed to be a replacement for
the standard isblank() function, which was thought to be "not very
portable yet". We can now assume that it's portable (it's in C99).
But pg_isblank() actually diverged from the standard isblank() by also
accepting '\r', while the standard one only accepts space and tab.
This was added to support parsing pg_hba.conf under Windows. But the
hba parsing code now works completely differently and already handles
line endings before we get to pg_isblank(). The other user of
pg_isblank() is for ident protocol message parsing, which also handles
'\r' separately. So this behavior is now obsolete and confusing.
To improve clarity, I separated those concerns. The ident parsing now
gets its own function that hardcodes the whitespace characters
mentioned by the relevant RFC. pg_isblank() is now static in hba.c
and is a wrapper around the standard isblank(), with some extra logic
to ensure robust treatment of non-ASCII characters.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/170308e6-a7a3-4484-87b2-f960bb564afa%40eisentraut.org
This commit introduces new internal bufmgr routines for marking shared
buffers as dirty:
* MarkDirtyUnpinnedBuffer()
* MarkDirtyRelUnpinnedBuffers()
* MarkDirtyAllUnpinnedBuffers()
These functions provide an efficient mechanism to respectively mark one
buffer, all the buffers of a relation, or the entire shared buffer pool
as dirty, something that can be useful to force patterns for the
checkpointer. MarkDirtyUnpinnedBufferInternal(), an extra routine, is
used by these three, to mark as dirty an unpinned buffer.
They are intended as developer tools to manipulate buffer dirtiness in
bulk, and will be used in a follow-up commit.
Author: Nazir Bilal Yavuz <byavuz81@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Aidar Imamov <a.imamov@postgrespro.ru>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Reviewed-by: Joseph Koshakow <koshy44@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Yuhang Qiu <iamqyh@gmail.com>
Reviewed-by: Xuneng Zhou <xunengzhou@gmail.com>
Discussion: https://postgr.es/m/CAN55FZ0h_YoSqqutxV6DES1RW8ig6wcA8CR9rJk358YRMxZFmw@mail.gmail.com
In v14, bb437f995 added support for scanning for ranges of TIDs using a
dedicated executor node for the purpose. Here, we allow these scans to
be parallelized. The range of blocks to scan is divvied up similarly to
how a Parallel Seq Scans does that, where 'chunks' of blocks are
allocated to each worker and the size of those chunks is slowly reduced
down to 1 block per worker by the time we're nearing the end of the
scan. Doing that means workers finish at roughly the same time.
Allowing TID Range Scans to be parallelized removes the dilemma from the
planner as to whether a Parallel Seq Scan will cost less than a
non-parallel TID Range Scan due to the CPU concurrency of the Seq Scan
(disk costs are not divided by the number of workers). It was possible
the planner could choose the Parallel Seq Scan which would result in
reading additional blocks during execution than the TID Scan would have.
Allowing Parallel TID Range Scans removes the trade-off the planner
makes when choosing between reduced CPU costs due to parallelism vs
additional I/O from the Parallel Seq Scan due to it scanning blocks from
outside of the required TID range. There is also, of course, the
traditional parallelism performance benefits to be gained as well, which
likely doesn't need to be explained here.
Author: Cary Huang <cary.huang@highgo.ca>
Author: David Rowley <dgrowleyml@gmail.com>
Reviewed-by: Junwang Zhao <zhjwpku@gmail.com>
Reviewed-by: Rafia Sabih <rafia.pghackers@gmail.com>
Reviewed-by: Steven Niu <niushiji@gmail.com>
Discussion: https://postgr.es/m/18f2c002a24.11bc2ab825151706.3749144144619388582@highgo.ca
This adds SupportRequestSimplifyAggref to allow pg_proc.prosupport
functions to receive an Aggref and allow them to determine if there is a
way that the Aggref call can be optimized.
Also added is a support function to allow transformation of COUNT(ANY)
into COUNT(*). This is possible to do when the given "ANY" cannot be
NULL and also that there are no ORDER BY / DISTINCT clauses within the
Aggref. This is a useful transformation to do as it is common that
people write COUNT(1), which until now has added unneeded overhead.
When counting a NOT NULL column. The overheads can be worse as that
might mean deforming more of the tuple, which for large fact tables may
be many columns in.
It may be possible to add prosupport functions for other aggregates. We
could consider if ORDER BY could be dropped for some calls, e.g. the
ORDER BY is quite useless in MAX(c ORDER BY c).
There is a little bit of passing fallout from adjusting
expr_is_nonnullable() to handle Const which results in a plan change in
the aggregates.out regression test. Previously, nothing was able to
determine that "One-Time Filter: (100 IS NOT NULL)" was always true,
therefore useless to include in the plan.
Author: David Rowley <dgrowleyml@gmail.com>
Reviewed-by: Corey Huinker <corey.huinker@gmail.com>
Reviewed-by: Matheus Alcantara <matheusssilv97@gmail.com>
Discussion: https://postgr.es/m/CAApHDvqGcPTagXpKfH=CrmHBqALpziThJEDs_MrPqjKVeDF9wA@mail.gmail.com
This commit renames write_chunk and read_chunk to respectively
pgstat_write_chunk() and pgstat_read_chunk(), along with the *_s
convenience macros.
These are made available for plug-ins, so as any code that decides to
write and/or read stats data can rely on a single code path for this
work.
Extracted from a larger patch by the same author.
Author: Sami Imseih <samimseih@gmail.com>
Discussion: https://postgr.es/m/CAA5RZ0s9SDOu+Z6veoJCHWk+kDeTktAtC-KY9fQ9Z6BJdDUirQ@mail.gmail.com
