Commit 9e8da0f7 taught nbtree to handle ScalarArrayOpExpr quals
natively. This works by pushing down the full context (the array keys)
to the nbtree index AM, enabling it to execute multiple primitive index
scans that the planner treats as one continuous index scan/index path.
This earlier enhancement enabled nbtree ScalarArrayOp index-only scans.
It also allowed scans with ScalarArrayOp quals to return ordered results
(with some notable restrictions, described further down).
Take this general approach a lot further: teach nbtree SAOP index scans
to decide how to execute ScalarArrayOp scans (when and where to start
the next primitive index scan) based on physical index characteristics.
This can be far more efficient. All SAOP scans will now reliably avoid
duplicative leaf page accesses (just like any other nbtree index scan).
SAOP scans whose array keys are naturally clustered together now require
far fewer index descents, since we'll reliably avoid starting a new
primitive scan just to get to a later offset from the same leaf page.
The scan's arrays now advance using binary searches for the array
element that best matches the next tuple's attribute value. Required
scan key arrays (i.e. arrays from scan keys that can terminate the scan)
ratchet forward in lockstep with the index scan. Non-required arrays
(i.e. arrays from scan keys that can only exclude non-matching tuples)
"advance" without the process ever rolling over to a higher-order array.
Naturally, only required SAOP scan keys trigger skipping over leaf pages
(non-required arrays cannot safely end or start primitive index scans).
Consequently, even index scans of a composite index with a high-order
inequality scan key (which we'll mark required) and a low-order SAOP
scan key (which we won't mark required) now avoid repeating leaf page
accesses -- that benefit isn't limited to simpler equality-only cases.
In general, all nbtree index scans now output tuples as if they were one
continuous index scan -- even scans that mix a high-order inequality
with lower-order SAOP equalities reliably output tuples in index order.
This allows us to remove a couple of special cases that were applied
when building index paths with SAOP clauses during planning.
Bugfix commit 807a40c5 taught the planner to avoid generating unsafe
path keys: path keys on a multicolumn index path, with a SAOP clause on
any attribute beyond the first/most significant attribute. These cases
are now all safe, so we go back to generating path keys without regard
for the presence of SAOP clauses (just like with any other clause type).
Affected queries can now exploit scan output order in all the usual ways
(e.g., certain "ORDER BY ... LIMIT n" queries can now terminate early).
Also undo changes from follow-up bugfix commit a4523c5a, which taught
the planner to produce alternative index paths, with path keys, but
without low-order SAOP index quals (filter quals were used instead).
We'll no longer generate these alternative paths, since they can no
longer offer any meaningful advantages over standard index qual paths.
Affected queries thereby avoid all of the disadvantages that come from
using filter quals within index scan nodes. They can avoid extra heap
page accesses from using filter quals to exclude non-matching tuples
(index quals will never have that problem). They can also skip over
irrelevant sections of the index in more cases (though only when nbtree
determines that starting another primitive scan actually makes sense).
There is a theoretical risk that removing restrictions on SAOP index
paths from the planner will break compatibility with amcanorder-based
index AMs maintained as extensions. Such an index AM could have the
same limitations around ordered SAOP scans as nbtree had up until now.
Adding a pro forma incompatibility item about the issue to the Postgres
17 release notes seems like a good idea.
Author: Peter Geoghegan <pg@bowt.ie>
Author: Matthias van de Meent <boekewurm+postgres@gmail.com>
Reviewed-By: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-By: Matthias van de Meent <boekewurm+postgres@gmail.com>
Reviewed-By: Tomas Vondra <tomas.vondra@enterprisedb.com>
Discussion: https://postgr.es/m/CAH2-Wz=ksvN_sjcnD1+Bt-WtifRA5ok48aDYnq3pkKhxgMQpcw@mail.gmail.com
When this bit of commentary was written, it was alluding to the
fact that we looked for newlines and EOD markers in the raw
(not yet encoding-converted) input data. We don't do that anymore,
preferring to batch the conversion of larger chunks of input and
split it into lines later. Hence there's no longer any need for
assumptions about the relevant characters being encoding-invariant,
and we should remove this comment saying we assume that.
Discussion: https://postgr.es/m/1461688.1712347668@sss.pgh.pa.us
After encountering the NUL terminator, the word-at-a-time loop exits
and we must hash the remaining bytes. Previously we calculated
the terminator's position and re-loaded the remaining bytes from
the input string. This was slower than the unaligned case for very
short strings. We already have all the data we need in a register,
so let's just mask off the bytes we need and hash them immediately.
In addition to endianness issues, the previous attempt upset valgrind
in the way it computed the mask. Whether by accident or by wisdom,
the author's proposed method passes locally with valgrind 3.22.
Ants Aasma, with cosmetic adjustments by me
Discussion: https://postgr.es/m/CANwKhkP7pCiW_5fAswLhs71-JKGEz1c1%2BPC0a_w1fwY4iGMqUA%40mail.gmail.com
This function previously used a mix of word-wise loads and bytewise
loads. The bytewise loads happened to be little-endian regardless of
platform. This in itself is not a problem. However, a future commit
will require the same result whether A) the input is loaded as a
word with the relevent bytes masked-off, or B) the input is loaded
one byte at a time.
While at it, improve debuggability of the internal hash state.
Discussion: https://postgr.es/m/CANWCAZZpuV1mES1mtSpAq8tWJewbrv4gEz6R_k4gzNG8GZ5gag%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
Remove duplicate hash_string_pointer() function definitions by creating
a new inline function hash_string() for this purpose.
This has the added advantage of avoiding strlen() calls when doing hash
lookup. It's not clear how many of these are perfomance-sensitive
enough to benefit from that, but the simplification is worth it on
its own.
Reviewed by Jeff Davis
Discussion: https://postgr.es/m/CANWCAZbg_XeSeY0a_PqWmWqeRATvzTzUNYRLeT%2Bbzs%2BYQdC92g%40mail.gmail.com
fasthash_accum_cstring_aligned() uses a technique, found in various
strlen() implementations, to detect a string's NUL terminator by
reading a word at at time. That triggers failures when testing with
"-fsanitize=address", at least with frontend code. To enable using
this function anywhere, add a function attribute macro to disable
such testing.
Reviewed by Jeff Davis
Discussion: https://postgr.es/m/CANWCAZbwvp7oUEkbw-xP4L0_S_WNKq-J-ucP4RCNDPJnrakUPw%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
The previous formula was incorrect in the case where the function's
nblocks argument was a multiple of BLOCKS_PER_CHUNK, which happens
whenever a relation segment file is exactly 512MB or exactly 1GB in
length. In such cases, the formula would calculate a stop_offset of
0 rather than 65536, resulting in modified blocks in the second half
of a 1GB file, or all the modified blocks in a 512MB file, being
omitted from the incremental backup.
Reported off-list by Tomas Vondra and Jakub Wartak.
Discussion: http://postgr.es/m/CA+TgmoYwy_KHp1-5GYNmVa=zdeJWhNH1T0SBmEuvqQNJEHj1Lw@mail.gmail.com
Fix a mistake in ac81101551 - write_reconstructed_file() called
copy_file_range() without properly checking HAVE_COPY_FILE_RANGE.
Reported by several macOS machines. Also reported by cfbot, but I missed
that issue before commit.
This commit allows using copy_file_range() for efficient combining of
data from multiple files, instead of simply reading/writing the blocks.
Depending on the filesystem and other factors (size of the increment,
distribution of modified blocks etc.) this may be faster than the
block-by-block copy, but more importantly it enables various features
provided by CoW filesystems.
If a checksum needs to be calculated for the file, the same strategy as
when copying whole files is used - copy_file_range is used to copy the
blocks, but the file is also read for the checksum calculation.
While the checksum calculation is rarely needed when cloning whole
files, when reconstructing the files from multiple backups it needs to
happen almost always (the only exception is when the user specified
--no-manifest).
Author: Tomas Vondra
Reviewed-by: Thomas Munro, Jakub Wartak, Robert Haas
Discussion: https://postgr.es/m/3024283a-7491-4240-80d0-421575f6bb23%40enterprisedb.com
Adds --clone/--copy-file-range options to pg_combinebackup, to allow
copying files using file cloning or copy_file_range(). These methods may
be faster than the standard block-by-block copy, but the main advantage
is that they enable various features provided by CoW filesystems.
This commit only uses these copy methods for files that did not change
and can be copied as a whole from a single backup.
These new copy methods may not be available on all platforms, in which
case the command throws an error (immediately, even if no files would be
copied as a whole). This early failure seems better than failing later
when trying to copy the first file, after performing a lot of work on
earlier files.
If the requested copy method is available, but a checksum needs to be
recalculated (e.g. because of a different checksum type), the file is
still copied using the requested method, but it is also read for the
checksum calculation. Depending on the filesystem this may be more
expensive than just performing the simple copy, but it does enable the
CoW benefits.
Initial patch by Jakub Wartak, various reworks and improvements by me.
Author: Tomas Vondra, Jakub Wartak
Reviewed-by: Thomas Munro, Jakub Wartak, Robert Haas
Discussion: https://postgr.es/m/3024283a-7491-4240-80d0-421575f6bb23%40enterprisedb.com
Buildfarm member caiman is showing this, which surprises me because
it's very late-model gcc (14.0.1) and ought to be smart enough to
know that elog(ERROR) doesn't return. But we're likely to see the
same from stupider compilers too, so add a dummy initialization in
our usual style.
The documentation index is getting very long, which makes it hard
to find things. Since these chapters are all very similar in structure
and content, merging them is a natural way of reducing the size of
the toplevel index.
Rather than actually combining all of the SGML into a single file,
keep one file per <sect1>, and add a glue file that includes all
of them.
Discussion: http://postgr.es/m/CA+Tgmob7_uoYuS2=rVwpVXaRwP-UXz+++saYTC-BCZ42QzSNKQ@mail.gmail.com
Align blocks stored in incremental files to BLCKSZ, so that the
incremental backups work well with CoW filesystems.
The header of the incremental file is padded with \0 to a multiple of
BLCKSZ, so that the block data (also BLCKSZ) is aligned to BLCKSZ. The
padding is added only to files containing block data, so files with just
the header remain small. This adds a bit of extra space, but as the
number of blocks increases the overhead gets negligible very quickly.
And as the padding is \0 bytes, it does compress extremely well.
The alignment is important for CoW filesystems that usually require the
blocks to be aligned to filesystem page size for features like block
sharing, deduplication etc. to work well. With the variable sized header
the blocks in the increments were not aligned at all, negating the
benefits of the CoW filesystems.
This matters even for non-CoW filesystems, for example when placed on a
RAID array. If the block is not aligned, it may easily span multiple
devices, causing read and write amplification.
It might be better to align the blocks to the filesystem page, not
BLCKSZ, but we have no good way to determine that. Even if we determine
the page size at the time of taking the backup, the backup may move. For
now the BLCKSZ seems sufficient - the filesystem page is usually 4K, so
the default BLCKSZ (8K by default) is aligned to that.
Author: Tomas Vondra
Reviewed-by: Robert Haas, Jakub Wartak
Discussion: https://postgr.es/m/3024283a-7491-4240-80d0-421575f6bb23%40enterprisedb.com
This removes the need to hold both the info_lck spinlock and
WALWriteLock to update them. We use stock atomic write instead, with
WALWriteLock held. Readers can use atomic read, without any locking.
This allows for some code to be reordered: some places were a bit
contorted to avoid repeated spinlock acquisition, but that's no longer a
concern, so we can turn them to more natural coding. Some further
changes are possible (maybe to performance wins), but in this commit I
did rather minimal ones only, to avoid increasing the blast radius.
Reviewed-by: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Reviewed-by: Jeff Davis <pgsql@j-davis.com>
Reviewed-by: Andres Freund <andres@anarazel.de> (earlier versions)
Discussion: https://postgr.es/m/20200831182156.GA3983@alvherre.pgsql
This commit does two things:
1) Maintains inactive_since for sync slots whenever the slot is released
just like any other regular slot.
2) Ensures the value is set to the current timestamp during the promotion
of standby to help correctly interpret the time after promotion. We don't
want the slots to appear inactive for a long time after promotion if they
haven't been synchronized recently. This would also avoid the invalidation
of such slots immediately after promotion if tomorrow we have a feature
that invalidates slots based on their inactivity time. Whoever acquires
the slot i.e. makes the slot active will reset it to NULL.
Author: Bharath Rupireddy
Reviewed-by: Bertrand Drouvot, Amit Kapila, Shveta Malik, Masahiko Sawada
Discussion: https://postgr.es/m/CAA4eK1KrPGwfZV9LYGidjxHeW+rxJ=E2ThjXvwRGLO=iLNuo=Q@mail.gmail.com
Discussion: https://postgr.es/m/CALj2ACW4aUe-_uFQOjdWCEN-xXoLGhmvRFnL8SNw_TZ5nJe+aw@mail.gmail.com
Discussion: https://postgr.es/m/CA+Tgmob_Ta-t2ty8QrKHBGnNLrf4ZYcwhGHGFsuUoFrAEDw4sA@mail.gmail.com
The current design behind the automatic generation of the C code and
documentation related to wait events introduced in fa88928470 does not
offer a way to attach new wait events without breaking ABI
compatibility, as all the events are forcibly reordered for each section
in the input file wait_event_names.txt. Adding new wait events to
stable branches is something that has happened in the past, 0b6517a3b7
being a recent example of that with VERSION_FILE_SYNC, so we need a way
to generate any C code for wait events while maintaining compatibility
on stable branches already released.
This commit solves this issue by adding a new region called
"ABI_compatibility" (keyword could be updated to something else if
someone had a better idea) to each section of wait_event_names.txt, so
as one can add new wait events to stable branches in
wait_event_names.txt while keeping the code ABI-compatible.
"ABI_compatibility" has no impact on the documentation generated: all
the wait events of one section are still alphabetically ordered. LWLock
and Lock sections generate their C code elsewhere, so they do not need
an "ABI_compatibility" region.
For example, let's imagine a wait_event_names.txt like that:
Section: ClassName - Foo
FOO_1 "Waiting in Foo 1"
FOO_2 "Waiting in Foo 2"
ABI_compatibility:
NEW_FOO_1 "Waiting in New Foo 1"
NEW_BAR_1 "Waiting in New Bar 1"
This results in the following enum, where the events in the ABI region
are listed last with the same ordering as in wait_event_names.txt:
typedef enum
{
WAIT_EVENT_FOO_1,
WAIT_EVENT_FOO_2,
WAIT_EVENT_NEW_FOO_1,
WAIT_EVENT_NEW_BAR_1
} WaitEventFoo;
New wait events added in stable branches should be added at the end of
each ABI_compatibility region, and ABI_compatibility should remain empty
on HEAD and unreleased stable branches.
This design has been suggested by Noah Misch and me.
Reported-by: Noah Misch
Author: Bertrand Drouvot
Reviewed-by: Michael Paquier
Discussion: https://postgr.es/m/20240317183114.16@rfd.leadboat.com
ecpg wants to emit a warning if it parses a SQL construct that the
backend can parse but will immediately throw a FEATURE_NOT_SUPPORTED
error for. The way it was testing for this was to see if the string
ERRCODE_FEATURE_NOT_SUPPORTED appeared anywhere in the gram.y code.
This is, of course, not nearly good enough, as there are plenty of
rules in gram.y that throw that error only conditionally. There was
a hack dating to 2008 to suppress the warning in one rule that
doesn't even exist anymore, but nothing for other cases we've created
since then. End result was that you could get "unsupported feature
will be passed to server" warnings while compiling perfectly good SQL
code in ecpg. Somehow we'd not heard complaints about this, but
it was exposed by the recent addition of an ecpg test for a SQL/JSON
construct.
To fix, suppress the warning if the rule contains any "if" statement.
Manual comparison of gram.y with the generated preproc.y file shows
that the warning is now emitted only in rules where it's sensible.
This problem has existed for a long time, so back-patch to all
supported branches.
Discussion: https://postgr.es/m/603615.1712245382@sss.pgh.pa.us
The link commands in test_json_parser/Makefile were a long way
shy of a load, as evidenced by buildfarm failures. Model them
on pgxs.mk's PROGRAM rule. (Probably we should have put these
two test programs in different subdirectories so we could
actually use the PROGRAM rule. But I won't question that
decision today.)
Add overlooked .gitignore entries.
Fix test_json_parser/Makefile to use the pgxs.mk clean rule
instead of fighting it. Suppresses a warning from make,
at least for me.
JSON_TABLE() allows JSON data to be converted into a relational view
and thus used, for example, in a FROM clause, like other tabular
data. Data to show in the view is selected from a source JSON object
using a JSON path expression to get a sequence of JSON objects that's
called a "row pattern", which becomes the source to compute the
SQL/JSON values that populate the view's output columns. Column
values themselves are computed using JSON path expressions applied to
each of the JSON objects comprising the "row pattern", for which the
SQL/JSON query functions added in 6185c9737c are used.
To implement JSON_TABLE() as a table function, this augments the
TableFunc and TableFuncScanState nodes that are currently used to
support XMLTABLE() with some JSON_TABLE()-specific fields.
Note that the JSON_TABLE() spec includes NESTED COLUMNS and PLAN
clauses, which are required to provide more flexibility to extract
data out of nested JSON objects, but they are not implemented here
to keep this commit of manageable size.
Author: Nikita Glukhov <n.gluhov@postgrespro.ru>
Author: Teodor Sigaev <teodor@sigaev.ru>
Author: Oleg Bartunov <obartunov@gmail.com>
Author: Alexander Korotkov <aekorotkov@gmail.com>
Author: Andrew Dunstan <andrew@dunslane.net>
Author: Amit Langote <amitlangote09@gmail.com>
Author: Jian He <jian.universality@gmail.com>
Reviewers have included (in no particular order):
Andres Freund, Alexander Korotkov, Pavel Stehule, Andrew Alsup,
Erik Rijkers, Zihong Yu, Himanshu Upadhyaya, Daniel Gustafsson,
Justin Pryzby, Álvaro Herrera, Jian He
Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru
Discussion: https://postgr.es/m/20220616233130.rparivafipt6doj3@alap3.anarazel.de
Discussion: https://postgr.es/m/abd9b83b-aa66-f230-3d6d-734817f0995d%40postgresql.org
Discussion: https://postgr.es/m/CA+HiwqE4XTdfb1nW=Ojoy_tQSRhYt-q_kb6i5d4xcKyrLC1Nbg@mail.gmail.com
This changes the three callers to json_parse_manifest() to use
json_parse_manifest_incremental_chunk() if appropriate. In the case of
the backend caller, since we don't know the size of the manifest in
advance we always call the incremental parser.
Author: Andrew Dunstan
Reviewed-By: Jacob Champion
Discussion: https://postgr.es/m/7b0a51d6-0d9d-7366-3a1a-f74397a02f55@dunslane.net
This adds the infrastructure for using the new non-recursive JSON parser
in processing manifests. It's important that callers make sure that the
last piece of json handed to the incremental manifest parser contains
the entire last few lines of the manifest, including the checksum.
Author: Andrew Dunstan
Reviewed-By: Jacob Champion
Discussion: https://postgr.es/m/7b0a51d6-0d9d-7366-3a1a-f74397a02f55@dunslane.net
This parser uses an explicit prediction stack, unlike the present
recursive descent parser where the parser state is represented on the
call stack. This difference makes the new parser suitable for use in
incremental parsing of huge JSON documents that cannot be conveniently
handled piece-wise by the recursive descent parser. One potential use
for this will be in parsing large backup manifests associated with
incremental backups.
Because this parser is somewhat slower than the recursive descent
parser, it is not replacing that parser, but is an additional parser
available to callers.
For testing purposes, if the build is done with -DFORCE_JSON_PSTACK, all
JSON parsing is done with the non-recursive parser, in which case only
trivial regression differences in error messages should be observed.
Author: Andrew Dunstan
Reviewed-By: Jacob Champion
Discussion: https://postgr.es/m/7b0a51d6-0d9d-7366-3a1a-f74397a02f55@dunslane.net
Commit 619bc23a1a introduced
WARNING: Project targets '>=0.54' but uses feature introduced in '0.55.0': Passing executable/found program object to script parameter of add_dist_script
Work around that by wrapping the offending line in a meson version check.
Author: Tristan Partin <tristan@neon.tech>
Discussion: https://www.postgresql.org/message-id/flat/D096Q3NFFVH1.1T5RE4MOO9ZFH%40neon.tech
This would cause the timestamp values used by emit_log_hook and all the
other log destinations to differ, because the timestamps are reset
before sending the logs to the server and after calling the hook.
This change matters for emit_log_hook when generating log information
with 'n' or 'm' in log_line_prefix through log_status_format(), or when
doing direct calls to get_formatted_log_time() like in the JSON or CSV
log formats.
While on it, this commit fixes a couple of comments related to the
formatted timestamps where the JSON was not mentioned. Oversight in
dc686681e0, that I have noticed while reviewing this patch.
Author: Kambam Vinay, Michael Paquier
Discussion: https://postgr.es/m/CANiRfmsK36A0i8mnQtzaxhSm3CUCimPwJPp4WQNq53OdSNkgWg@mail.gmail.com
To allow the use of the read stream API added in b5a9b18cd for
sequential scans on heap tables, here we make some adjustments to make
that change less invasive and perhaps make the code easier to follow in
the process.
Here heapgetpage() gets broken into two functions:
1) The part which reads the block has now been moved into a function
named heapfetchbuf().
2) The part which performed pruning and populated the scan's
rs_vistuples[] array is now moved into a new function named
heap_prepare_pagescan().
The functionality provided by heap_prepare_pagescan() was only ever
required by SO_ALLOW_PAGEMODE scans, so the branching that was
previously done in heapgetpage() is no longer needed as we simply just
don't call heap_prepare_pagescan() from heapgettup() in the refactored
code.
Author: Melanie Plageman
Discussion: https://postgr.es/m/CAAKRu_YtXJiYKQvb5JsA2SkwrsizYLugs4sSOZh3EAjKUg=gEQ@mail.gmail.com
emit_tap_output_v() includes some fprintf() calls for some output
related to the TAP protocol, that may clobber errno and break %m. This
commit makes the logging of pg_regress smarter by saving errno before
restoring it in vfprintf() where the input strings are used, removing
the need for strerror(). All logs are switched to %m rather than
strerror(), shaving some code.
This was not a problem until now as pg_regress.c did not use %m, but the
change is simple enough that we have no reason to not support this
placeholder, and that will avoid future mistakes if new logs that
include %m are added.
Author: Dagfinn Ilmari Mannsåker
Reviewed-by: Peter Eisentraunt, Michael Paquier
Discussion: https://postgr.es/m/87sf13jhuw.fsf@wibble.ilmari.org
EXPLAIN (ANALYZE, SERIALIZE) allows collection of statistics about
the volume of data emitted by a query, as well as the time taken
to convert the data to the on-the-wire format. Previously there
was no way to investigate this without actually sending the data
to the client, in which case network transmission costs might
swamp what you wanted to see. In particular this feature allows
investigating the costs of de-TOASTing compressed or out-of-line
data during formatting.
Stepan Rutz and Matthias van de Meent,
reviewed by Tomas Vondra and myself
Discussion: https://postgr.es/m/ca0adb0e-fa4e-c37e-1cd7-91170b18cae1@gmx.de
After this change we have XLogCtl->logWriteResult and ->logFlushResult.
There's no functional change, other than the fact that the assignment
from shared memory to local is no longer done via struct assignment, but
instead using a macro that copies each member separately.
The current representation is inconvenient going forward; notably, we
would like to add a new member "Copy" (to keep track of the last
position copied into WAL buffers), so the symmetry between the values in
shared memory vs. those in local would be lost.
This also gives us freedom to later change the concurrency model for the
values in shared memory: we can make them use atomics instead of relying
on the info_lck spinlock.
Reviewed-by: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Discussion: https://postgr.es/m/202404031119.cd2kugjk2vho@alvherre.pgsql
