Commit Graph

971 Commits

Author SHA1 Message Date
Daniel Gustafsson e00bc6c922 doc: Add default value of createrole_self_grant
Document that the default value for createrole_self_grant is an empty
string which in turn disable the feature.

Author: Shi Yu <shiy.fnst@fujitsu.com>
Discussion: https://postgr.es/m/OSZPR01MB63105D0D96A9A72A7FCD4FFEFDA09@OSZPR01MB6310.jpnprd01.prod.outlook.com
2023-02-22 11:05:20 +01:00
David Rowley 5352ca22e0 Rename force_parallel_mode to debug_parallel_query
force_parallel_mode is meant to be used to allow us to exercise the
parallel query infrastructure to ensure that it's working as we expect.
It seems some users think this GUC is for forcing the query planner into
picking a parallel plan regardless of the costs.  A quick look at the
documentation would have made them realize that they were wrong, but the
GUC is likely too conveniently named which, evidently, seems to often
result in users expecting that it forces the planner into usefully
parallelizing queries.

Here we rename the GUC to something which casual users are less likely to
mistakenly think is what they need to make their query run more quickly.

For now, the old name can still be used.  We'll revisit if the old name
mapping can be removed once the buildfarm configs are all updated.

Reviewed-by: John Naylor
Discussion: https://postgr.es/m/CAApHDvrsOi92_uA7PEaHZMH-S4Xv+MGhQWA+GrP8b1kjpS1HjQ@mail.gmail.com
2023-02-15 21:21:59 +13:00
Michael Paquier ef7002dbe0 Fix various typos in code and tests
Most of these are recent, and the documentation portions are new as of
v16 so there is no need for a backpatch.

Author: Justin Pryzby
Discussion: https://postgr.es/m/20230208155644.GM1653@telsasoft.com
2023-02-09 14:43:53 +09:00
Thomas Munro 117d2604c2 Doc: Abstract AF_UNIX sockets don't work on Windows.
An early release of AF_UNIX in Windows apparently supported Linux-style
"abstract" Unix sockets, but they do not seem to work in current Windows
versions and there is no mention of any of this in the Winsock
documentation.  Remove the mention of Windows from the documentation.

Back-patch to 14, where commit c9f0624b landed.

Discussion: https://postgr.es/m/CA%2BhUKGKrYbSZhrk4NGfoQGT_3LQS5pC5KNE1g0tvE_pPBZ7uew%40mail.gmail.com
2023-02-02 18:25:10 +13:00
Amit Kapila 9f2213a7c5 Allow the logical_replication_mode to be used on the subscriber.
Extend the existing developer option 'logical_replication_mode' to help
test the parallel apply of large transactions on the subscriber.

When set to 'buffered', the leader sends changes to parallel apply workers
via a shared memory queue. When set to 'immediate', the leader serializes
all changes to files and notifies the parallel apply workers to read and
apply them at the end of the transaction.

This helps in adding tests to cover the serialization code path in
parallel streaming mode.

Author: Hou Zhijie
Reviewed-by: Peter Smith, Kuroda Hayato, Sawada Masahiko, Amit Kapila
Discussion: https://postgr.es/m/CAA4eK1+wyN6zpaHUkCLorEWNx75MG0xhMwcFhvjqm2KURZEAGw@mail.gmail.com
2023-02-02 08:15:18 +05:30
Amit Kapila 1e8b61735c Rename GUC logical_decoding_mode to logical_replication_mode.
Rename the developer option 'logical_decoding_mode' to the more flexible
name 'logical_replication_mode' because doing so will make it easier to
extend this option in the future to help test other areas of logical
replication.

Currently, it is used on the publisher side to allow streaming or
serializing each change in logical decoding. In the upcoming patch, we are
planning to use it on the subscriber. On the subscriber, it will allow
serializing the changes to file and notifies the parallel apply workers to
read and apply them at the end of the transaction.

We discussed exposing this parameter as a subscription option but
it did not seem advisable since it is primarily used for testing/debugging
and there is no other such parameter. We also discussed having separate
GUCs for publisher and subscriber but for current testing/debugging
requirements, one GUC is sufficient.

Author: Hou Zhijie
Reviewed-by: Peter Smith, Kuroda Hayato, Sawada Masahiko, Amit Kapila
Discussion: https://postgr.es/m/CAD21AoAy2c=Mx=FTCs+EwUsf2kQL5MmU3N18X84k0EmCXntK4g@mail.gmail.com
Discussion: https://postgr.es/m/CAA4eK1+wyN6zpaHUkCLorEWNx75MG0xhMwcFhvjqm2KURZEAGw@mail.gmail.com
2023-01-30 08:02:08 +05:30
Peter Geoghegan 6c6b497266 Revert "Add eager and lazy freezing strategies to VACUUM."
This reverts commit 4d41799261.  Broad
concerns about regressions caused by eager freezing strategy have been
raised.  Whether or not these concerns can be worked through in any time
frame is far from certain.

Discussion: https://postgr.es/m/20230126004347.gepcmyenk2csxrri@awork3.anarazel.de
2023-01-25 22:22:27 -08:00
Peter Geoghegan 4d41799261 Add eager and lazy freezing strategies to VACUUM.
Eager freezing strategy avoids large build-ups of all-visible pages.  It
makes VACUUM trigger page-level freezing whenever doing so will enable
the page to become all-frozen in the visibility map.  This is useful for
tables that experience continual growth, particularly strict append-only
tables such as pgbench's history table.  Eager freezing significantly
improves performance stability by spreading out the cost of freezing
over time, rather than doing most freezing during aggressive VACUUMs.
It complements the insert autovacuum mechanism added by commit b07642db.

VACUUM determines its freezing strategy based on the value of the new
vacuum_freeze_strategy_threshold GUC (or reloption) with logged tables.
Tables that exceed the size threshold use the eager freezing strategy.
Unlogged tables and temp tables always use eager freezing strategy,
since the added cost is negligible there.  Non-permanent relations won't
incur any extra overhead in WAL written (for the obvious reason), nor in
pages dirtied (since any extra freezing will only take place on pages
whose PD_ALL_VISIBLE bit needed to be set either way).

VACUUM uses lazy freezing strategy for logged tables that fall under the
GUC size threshold.  Page-level freezing triggers based on the criteria
established in commit 1de58df4, which added basic page-level freezing.

Eager freezing is strictly more aggressive than lazy freezing.  Settings
like vacuum_freeze_min_age still get applied in just the same way in
every VACUUM, independent of the strategy in use.  The only mechanical
difference between eager and lazy freezing strategies is that only the
former applies its own additional criteria to trigger freezing pages.
Note that even lazy freezing strategy will trigger freezing whenever a
page happens to have required that an FPI be written during pruning,
provided that the page will thereby become all-frozen in the visibility
map afterwards (due to the FPI optimization from commit 1de58df4).

The vacuum_freeze_strategy_threshold default setting is 4GB.  This is a
relatively low setting that prioritizes performance stability.  It will
be reviewed at the end of the Postgres 16 beta period.

Author: Peter Geoghegan <pg@bowt.ie>
Reviewed-By: Jeff Davis <pgsql@j-davis.com>
Reviewed-By: Andres Freund <andres@anarazel.de>
Reviewed-By: Matthias van de Meent <boekewurm+postgres@gmail.com>
Discussion: https://postgr.es/m/CAH2-WzkFok_6EAHuK39GaW4FjEFQsY=3J0AAd6FXk93u-Xq3Fg@mail.gmail.com
2023-01-25 14:15:38 -08:00
Tom Lane 5a3a95385b Track logrep apply workers' last start times to avoid useless waits.
Enforce wal_retrieve_retry_interval on a per-subscription basis,
rather than globally, and arrange to skip that delay in case of
an intentional worker exit.  This probably makes little difference
in the field, where apply workers wouldn't be restarted often;
but it has a significant impact on the runtime of our logical
replication regression tests (even though those tests use
artificially-small wal_retrieve_retry_interval settings already).

Nathan Bossart, with mostly-cosmetic editorialization by me

Discussion: https://postgr.es/m/20221122004119.GA132961@nathanxps13
2023-01-22 14:08:46 -05:00
Robert Haas 6e2775e4d4 Add new GUC reserved_connections.
This provides a way to reserve connection slots for non-superusers.
The slots reserved via the new GUC are available only to users who
have the new predefined role pg_use_reserved_connections.
superuser_reserved_connections remains as a final reserve in case
reserved_connections has been exhausted.

Patch by Nathan Bossart. Reviewed by Tushar Ahuja and by me.

Discussion: http://postgr.es/m/20230119194601.GA4105788@nathanxps13
2023-01-20 15:39:13 -05:00
Robert Haas 6c1d5ba486 Update docs and error message for superuser_reserved_connections.
Commit ea92368cd1 made max_wal_senders
a separate pool of backends from max_connections, but the documentation
and error message for superuser_reserved_connections weren't updated
at the time, and as a result are somewhat misleading. Update.

This is arguably a back-patchable bug fix, but because it seems quite
minor, no back-patch.

Patch by Nathan Bossart. Reviewed by Tushar Ahuja and by me.

Discussion: http://postgr.es/m/20230119194601.GA4105788@nathanxps13
2023-01-20 15:23:04 -05:00
Tom Lane 09d465c397 Doc: fix a few oddly-spelled SGML ID attributes.
Avoid use of "_" in SGML IDs.  Awhile back that was actually
disallowed by the toolchain, as a consequence of which our convention
has been to use "-" instead.  Fix a couple of stragglers that are
particularly inconsistent with that convention and with related IDs.

This is just neatnik-ism, so no need for back-patch.

Discussion: https://postgr.es/m/769446.1673478332@sss.pgh.pa.us
2023-01-17 17:13:20 -05:00
Robert Haas e5b8a4c098 Add new GUC createrole_self_grant.
Can be set to the empty string, or to either or both of "set" or
"inherit". If set to a non-empty value, a non-superuser who creates
a role (necessarily by relying up the CREATEROLE privilege) will
grant that role back to themselves with the specified options.

This isn't a security feature, because the grant that this feature
triggers can also be performed explicitly. Instead, it's a user experience
feature. A superuser would necessarily inherit the privileges of any
created role and be able to access all such roles via SET ROLE;
with this patch, you can configure createrole_self_grant = 'set, inherit'
to provide a similar experience for a user who has CREATEROLE but not
SUPERUSER.

Discussion: https://postgr.es/m/CA+TgmobN59ct+Emmz6ig1Nua2Q-_o=r6DSD98KfU53kctq_kQw@mail.gmail.com
2023-01-10 12:44:49 -05:00
Tom Lane 78ee60ed84 Doc: add XML ID attributes to <sectN> and <varlistentry> tags.
This doesn't have any external effect at the moment, but it
will allow adding useful link-discoverability features later.

Brar Piening, reviewed by Karl Pinc.

Discussion: https://postgr.es/m/CAB8KJ=jpuQU9QJe4+RgWENrK5g9jhoysMw2nvTN_esoOU0=a_w@mail.gmail.com
2023-01-09 15:08:24 -05:00
Amit Kapila 216a784829 Perform apply of large transactions by parallel workers.
Currently, for large transactions, the publisher sends the data in
multiple streams (changes divided into chunks depending upon
logical_decoding_work_mem), and then on the subscriber-side, the apply
worker writes the changes into temporary files and once it receives the
commit, it reads from those files and applies the entire transaction. To
improve the performance of such transactions, we can instead allow them to
be applied via parallel workers.

In this approach, we assign a new parallel apply worker (if available) as
soon as the xact's first stream is received and the leader apply worker
will send changes to this new worker via shared memory. The parallel apply
worker will directly apply the change instead of writing it to temporary
files. However, if the leader apply worker times out while attempting to
send a message to the parallel apply worker, it will switch to
"partial serialize" mode -  in this mode, the leader serializes all
remaining changes to a file and notifies the parallel apply workers to
read and apply them at the end of the transaction. We use a non-blocking
way to send the messages from the leader apply worker to the parallel
apply to avoid deadlocks. We keep this parallel apply assigned till the
transaction commit is received and also wait for the worker to finish at
commit. This preserves commit ordering and avoid writing to and reading
from files in most cases. We still need to spill if there is no worker
available.

This patch also extends the SUBSCRIPTION 'streaming' parameter so that the
user can control whether to apply the streaming transaction in a parallel
apply worker or spill the change to disk. The user can set the streaming
parameter to 'on/off', or 'parallel'. The parameter value 'parallel' means
the streaming will be applied via a parallel apply worker, if available.
The parameter value 'on' means the streaming transaction will be spilled
to disk. The default value is 'off' (same as current behaviour).

In addition, the patch extends the logical replication STREAM_ABORT
message so that abort_lsn and abort_time can also be sent which can be
used to update the replication origin in parallel apply worker when the
streaming transaction is aborted. Because this message extension is needed
to support parallel streaming, parallel streaming is not supported for
publications on servers < PG16.

Author: Hou Zhijie, Wang wei, Amit Kapila with design inputs from Sawada Masahiko
Reviewed-by: Sawada Masahiko, Peter Smith, Dilip Kumar, Shi yu, Kuroda Hayato, Shveta Mallik
Discussion: https://postgr.es/m/CAA4eK1+wyN6zpaHUkCLorEWNx75MG0xhMwcFhvjqm2KURZEAGw@mail.gmail.com
2023-01-09 07:52:45 +05:30
Peter Geoghegan 1de58df4fe Add page-level freezing to VACUUM.
Teach VACUUM to decide on whether or not to trigger freezing at the
level of whole heap pages.  Individual XIDs and MXIDs fields from tuple
headers now trigger freezing of whole pages, rather than independently
triggering freezing of each individual tuple header field.

Managing the cost of freezing over time now significantly influences
when and how VACUUM freezes.  The overall amount of WAL written is the
single most important freezing related cost, in general.  Freezing each
page's tuples together in batch allows VACUUM to take full advantage of
the freeze plan WAL deduplication optimization added by commit 9e540599.

Also teach VACUUM to trigger page-level freezing whenever it detects
that heap pruning generated an FPI.  We'll have already written a large
amount of WAL just to do that much, so it's very likely a good idea to
get freezing out of the way for the page early.  This only happens in
cases where it will directly lead to marking the page all-frozen in the
visibility map.

In most cases "freezing a page" removes all XIDs < OldestXmin, and all
MXIDs < OldestMxact.  It doesn't quite work that way in certain rare
cases involving MultiXacts, though.  It is convenient to define "freeze
the page" in a way that gives FreezeMultiXactId the leeway to put off
the work of processing an individual tuple's xmax whenever it happens to
be a MultiXactId that would require an expensive second pass to process
aggressively (allocating a new multi is especially worth avoiding here).
FreezeMultiXactId is eager when processing is cheap (as it usually is),
and lazy in the event of an individual multi that happens to require
expensive second pass processing.  This avoids regressions related to
processing of multis that page-level freezing might otherwise cause.

Author: Peter Geoghegan <pg@bowt.ie>
Reviewed-By: Jeff Davis <pgsql@j-davis.com>
Reviewed-By: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CAH2-WzkFok_6EAHuK39GaW4FjEFQsY=3J0AAd6FXk93u-Xq3Fg@mail.gmail.com
2022-12-28 08:50:47 -08:00
Amit Kapila 5de94a041e Add 'logical_decoding_mode' GUC.
This enables streaming or serializing changes immediately in logical
decoding. This parameter is intended to be used to test logical decoding
and replication of large transactions for which otherwise we need to
generate the changes till logical_decoding_work_mem is reached.

This helps in reducing the timing of existing tests related to logical
replication of in-progress transactions and will help in writing tests for
for the upcoming feature for parallelly applying large in-progress
transactions.

Author: Shi yu
Reviewed-by: Sawada Masahiko, Shveta Mallik, Amit Kapila, Dilip Kumar, Kuroda Hayato, Kyotaro Horiguchi
Discussion: https://postgr.es/m/OSZPR01MB63104E7449DBE41932DB19F1FD1B9@OSZPR01MB6310.jpnprd01.prod.outlook.com
2022-12-26 08:58:16 +05:30
David Rowley 3226f47282 Add enable_presorted_aggregate GUC
1349d279 added query planner support to allow more efficient execution of
aggregate functions which have an ORDER BY or a DISTINCT clause.  Prior to
that commit, the planner would only request that the lower planner produce
a plan with the order required for the GROUP BY clause and it would be
left up to nodeAgg.c to perform the final sort of records within each
group so that the aggregate transition functions were called in the
correct order.  Now that the planner requests the lower planner produce a
plan with the GROUP BY and the ORDER BY / DISTINCT aggregates in mind,
there is the possibility that the planner chooses a plan which could be
less efficient than what would have been produced before 1349d279.

While developing 1349d279, I had in mind that Incremental Sort would help
us in cases where an index exists only on the GROUP BY column(s).
Incremental Sort would just replace the implicit tuplesorts which are
being performed in nodeAgg.c.  However, because the planner has the
flexibility to instead choose a plan which just performs a full sort on
both the GROUP BY and ORDER BY / DISTINCT aggregate columns, there is
potential for the planner to make a bad choice.  The costing for
Incremental Sort is not perfect as it assumes an even distribution of rows
to sort within each sort group.

Here we add an escape hatch in the form of the enable_presorted_aggregate
GUC.  This will allow users to get the pre-PG16 behavior in cases where
they have no other means to convince the query planner to produce a plan
which only sorts on the GROUP BY column(s).

Discussion: https://postgr.es/m/CAApHDvr1Sm+g9hbv4REOVuvQKeDWXcKUAhmbK5K+dfun0s9CvA@mail.gmail.com
2022-12-20 22:28:58 +13:00
Alvaro Herrera a8500750ca
Better document logical replication parameters
Add some cross-links between chapter "20. Server Parameters" and
"31. Logical Replication" regarding the available configuration
parameters, for easier navigation; and some more explanatory text too.

I (Álvaro) chose to duplicate max_replication_slots in Chapter 20,
because it has completely different meanings at each side of the
replication link.

Author: Peter Smith <smithpb2250@gmail.com>
Reviewed-by: vignesh C <vignesh21@gmail.com>
Reviewed-by: samay sharma <smilingsamay@gmail.com>
Discussion: https://postgr.es/m/CAHut+PsESqpy7w3Y6cX98c255ZuCjvipkhKjy6hZBjOv4E6iJA@mail.gmail.com
2022-12-12 20:18:56 +01:00
Michael Paquier 8a476fda5e doc: Add missing <varlistentry> markups for developer GUCs
Missing such markups makes it impossible to create links back to these
GUCs, and all the other parameters have one already.

Author: Ian Lawrence Barwick
Discussion: https://postgr.es/m/CAB8KJ=jx=6dFB_EN3j0UkuvG3cPu5OmQiM-ZKRAz+fKvS+u8Ng@mail.gmail.com
Backpatch-through: 11
2022-12-05 11:23:08 +09:00
Bruce Momjian 66bc9d2d3e doc: add transaction processing chapter with internals info
This also adds references to this new chapter at relevant sections of
our documentation.  Previously much of these internal details were
exposed to users, but not explained.  This also updates RELEASE
SAVEPOINT.

Discussion: https://postgr.es/m/CANbhV-E_iy9fmrErxrCh8TZTyenpfo72Hf_XD2HLDppva4dUNA@mail.gmail.com

Author: Simon Riggs, Laurenz Albe

Reviewed-by: Bruce Momjian

Backpatch-through: 11
2022-11-29 20:49:52 -05:00
Thomas Munro cd4329d939 Remove promote_trigger_file.
Previously, an idle startup (recovery) process would wake up every 5
seconds to have a chance to poll for promote_trigger_file, even if that
GUC was not configured.  That promotion triggering mechanism was
effectively superseded by pg_ctl promote and pg_promote() a long time
ago.  There probably aren't many users left and it's very easy to change
to the modern mechanisms, so we agreed to remove the feature.

This is part of a campaign to reduce wakeups on idle systems.

Author: Simon Riggs <simon.riggs@enterprisedb.com>
Reviewed-by: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Reviewed-by: Thomas Munro <thomas.munro@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Ian Lawrence Barwick <barwick@gmail.com>
Discussion: https://postgr.es/m/CANbhV-FsjnzVOQGBpQ589%3DnWuL1Ex0Ykn74Nh1hEjp2usZSR5g%40mail.gmail.com
2022-11-29 12:08:38 +13:00
Daniel Gustafsson 1f059a4408 doc: Clarify unit of logging for log_temp_files
When the unit is omitted from log_temp_files the value is taken as kb,
but the logged value is also without unit but specified in bytes. This
could cause some confusion, so clarify in the documentation which unit
is used when logging.

Reported-by: iphatiey5eu2au6@pasms.be
Reviewed-by: Bruce Momjian <bruce@momjian.us>
Discussion: https://postgr.es/m/166859439833.632.13122583000472281400@wrigleys.postgresql.org
2022-11-28 11:10:01 +01:00
Tom Lane 51b5834cd5 Provide options for postmaster to kill child processes with SIGABRT.
The postmaster normally sends SIGQUIT to force-terminate its
child processes after a child crash or immediate-stop request.
If that doesn't result in child exit within a few seconds,
we follow it up with SIGKILL.  This patch provides GUC flags
that allow either of these signals to be replaced with SIGABRT.
On typically-configured Unix systems, that will result in a
core dump being produced for each such child.  This can be
useful for debugging problems, although it's not something you'd
want to have on in production due to the risk of disk space
bloat from lots of core files.

The old postmaster -T switch, which sent SIGSTOP in place of
SIGQUIT, is changed to be the same as send_abort_for_crash.
As far as I can tell from the code comments, the intent of
that switch was just to block things for long enough to force
core dumps manually, which seems like an unnecessary extra step.
(Maybe at the time, there was no way to get most kernels to
produce core files with per-PID names, requiring manual core
file renaming after each one.  But now it's surely the hard way.)

I also took the opportunity to remove the old postmaster -n
(skip shmem reinit) switch, which hasn't actually done anything
in decades, though the documentation still claimed it did.

Discussion: https://postgr.es/m/2251016.1668797294@sss.pgh.pa.us
2022-11-21 11:59:29 -05:00
Peter Eisentraut d627ce3b70 Disallow setting archive_library and archive_command at the same time
Setting archive_library and archive_command at the same time is now an
error.  Before, archive_library would take precedence over
archive_command.

Author: Nathan Bossart <nathandbossart@gmail.com>
Reviewed-by: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Reviewed-by: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Discussion: https://www.postgresql.org/message-id/20220914222736.GA3042279%40nathanxps13
2022-11-15 10:03:47 +01:00
Michael Paquier f186c7c885 doc: Fix type of cursor_position in jsonlog table
This entry was listed as a "string", but it is a "number.  The other
fields are correctly described, on a second look.

Reported-by: Nuko Yokohama
Author: Tatsuo Ishii
Discussion: https://postgr.es/m/CAF3Gu1awoVoDP5d0_eN=cR=QkGVwH+OtFvwJkkc5cB_ZMWjyeA@mail.gmail.com
Backpatch-through: 15
2022-10-25 09:29:21 +09:00
Michael Paquier 9668c4a661 Rework shutdown callback of archiver modules
As currently designed, with a callback registered in a ERROR_CLEANUP
block, the shutdown callback would get called twice when updating
archive_library on SIGHUP, which is something that we want to avoid to
ease the life of extension writers.

Anyway, an ERROR in the archiver process is treated as a FATAL, stopping
it immediately, hence there is no need for a ERROR_CLEANUP block.
Instead of that, the shutdown callback is not called upon
before_shmem_exit(), giving to the modules the opportunity to do any
cleanup actions before the server shuts down its subsystems.

While on it, this commit adds some testing coverage for the shutdown
callback.  Neither shell_archive nor basic_archive have been using it,
and one is added to shell_archive, whose trigger is checked in a TAP
test through a shutdown sequence.

Author: Nathan Bossart, Bharath Rupireddy
Reviewed-by: Kyotaro Horiguchi, Michael Paquier
Discussion: https://postgr.es/m/20221015221328.GB1821022@nathanxps13
Backpatch-through: 15
2022-10-19 14:06:56 +09:00
Bruce Momjian 23f3989d92 doc: clarify description for log_startup_progress_interval
Reported-by: Elena Indrupskaya

Discussion: https://postgr.es/m/0af43b49-1646-93d0-ccf1-bb3c635c8c6f@postgrespro.ru

Author: Elena Indrupskaya

Backpatch-through: 15
2022-10-05 15:53:40 -04:00
Tom Lane f4c7c410ee Revert "Optimize order of GROUP BY keys".
This reverts commit db0d67db24 and
several follow-on fixes.  The idea of making a cost-based choice
of the order of the sorting columns is not fundamentally unsound,
but it requires cost information and data statistics that we don't
really have.  For example, relying on procost to distinguish the
relative costs of different sort comparators is pretty pointless
so long as most such comparator functions are labeled with cost 1.0.
Moreover, estimating the number of comparisons done by Quicksort
requires more than just an estimate of the number of distinct values
in the input: you also need some idea of the sizes of the larger
groups, if you want an estimate that's good to better than a factor of
three or so.  That's data that's often unknown or not very reliable.
Worse, to arrive at estimates of the number of calls made to the
lower-order-column comparison functions, the code needs to make
estimates of the numbers of distinct values of multiple columns,
which are necessarily even less trustworthy than per-column stats.
Even if all the inputs are perfectly reliable, the cost algorithm
as-implemented cannot offer useful information about how to order
sorting columns beyond the point at which the average group size
is estimated to drop to 1.

Close inspection of the code added by db0d67db2 shows that there
are also multiple small bugs.  These could have been fixed, but
there's not much point if we don't trust the estimates to be
accurate in-principle.

Finally, the changes in cost_sort's behavior made for very large
changes (often a factor of 2 or so) in the cost estimates for all
sorting operations, not only those for multi-column GROUP BY.
That naturally changes plan choices in many situations, and there's
precious little evidence to show that the changes are for the better.
Given the above doubts about whether the new estimates are really
trustworthy, it's hard to summon much confidence that these changes
are better on the average.

Since we're hard up against the release deadline for v15, let's
revert these changes for now.  We can always try again later.

Note: in v15, I left T_PathKeyInfo in place in nodes.h even though
it's unreferenced.  Removing it would be an ABI break, and it seems
a bit late in the release cycle for that.

Discussion: https://postgr.es/m/TYAPR01MB586665EB5FB2C3807E893941F5579@TYAPR01MB5866.jpnprd01.prod.outlook.com
2022-10-03 10:56:16 -04:00
Tom Lane 5f1048881d Doc: minor cleanups.
Improve a couple of things I noticed while working on v15
release notes.
2022-09-23 18:20:14 -04:00
Peter Eisentraut ba50834551 Restore archive_command documentation
Commit 5ef1eefd76, which added
archive_library, purged most mentions of archive_command from the
documentation.  This is inappropriate, since archive_command is still
a feature in use and users will want to see information about it.

This restores all the removed mentions and rephrases things so that
archive_command and archive_library are presented as alternatives of
each other.

Reviewed-by: Nathan Bossart <nathandbossart@gmail.com>
Discussion: https://www.postgresql.org/message-id/9366d634-a917-85a9-4991-b2a4859edaf9@enterprisedb.com
2022-09-22 07:35:00 -04:00
Tom Lane 31dcfae83c Use the terminology "WAL file" not "log file" more consistently.
Referring to the WAL as just "log" invites confusion with the
postmaster log, so avoid doing that in docs and error messages.
Also shorten "WAL segment file" to just "WAL file" in various
places.

Bharath Rupireddy, reviewed by Nathan Bossart and Kyotaro Horiguchi

Discussion: https://postgr.es/m/CALj2ACUeXa8tDPaiTLexBDMZ7hgvaN+RTb957-cn5qwv9zf-MQ@mail.gmail.com
2022-09-14 18:40:58 -04:00
Peter Eisentraut 111d954024 Small wording improvements 2022-09-14 22:56:55 +02:00
Bruce Momjian 115464bb5b doc: add section about heap-only tuples (HOT)
Reported-by: Jonathan S. Katz

Discussion: https://postgr.es/m/c59ffbd5-96ac-a5a5-a401-14f627ca1405@postgresql.org

Backpatch-through: 11
2022-08-12 15:05:13 -04:00
Bruce Momjian 50e088d6f2 doc: warn about security issues around log files
Reported-by: Simon Riggs

Discussion: https://postgr.es/m/CANP8+jJESuuXYq9Djvf-+tx2vY2OFLmfEuu+UvwHNJ1RT7iJCQ@mail.gmail.com

Author: Simon Riggs

Backpatch-through: 10
2022-08-12 12:02:21 -04:00
Bruce Momjian 4d807bbc4b doc: improve wal_level docs for the 'minimal' level
Reported-by: David G. Johnston

Discussion: https://postgr.es/m/CAKFQuwZ24UcfkoyLLSW3PMGQATomOcw1nuYFRuMev-NoOF+mYw@mail.gmail.com

Author: David G. Johnston

Backpatch-through: 14, partial to 13
2022-08-12 10:30:01 -04:00
Michael Paquier 0b039e3a84 Fix some inconsistencies with GUC categories
This commit addresses a few things around GUCs:
- The TCP-related parameters (the four tcp_keepalives_* and
client_connection_check_interval are listed in postgresql.conf.sample in
a subsection called "TCP settings" of "CONNECTIONS AND AUTHENTICATION",
but they did not have their own group name in guc.c.
- enable_group_by_reordering, stats_fetch_consistency and
recovery_prefetch had an inconsistent description, missing a dot at the
end.
- In postgresql.conf.sample, "Process title" should not have a section
of its own, but it should be a subsection of "REPORTING AND LOGGING".

This impacts the contents of pg_settings, which could be seen as a
compatibility break, so no backpatch is done.  This is similar to the
cleanup done in a55a984.

Author: Shinya Kato
Discussion: https://postgr.es/m/5e0c9c608624eafbba910c344282cb14@oss.nttdata.com
2022-08-09 20:01:44 +09:00
Alexander Korotkov f77ff08335 Document the ability to specify TableAM for pgbench
Upcoming custom Table Access Methods (TableAM) need benchmarking.  Despite
pgbench doesn't have an explicit option for TableAM specification, one can
specify it using PGOPTION environmental variable.  The present commit documents
this way to specify TableAM for pgbench.

Discussion: https://postgr.es/m/CAC77N6ih%3DLbhZQXV76grEsaVQkBL464Y2Foqq9o%3Df4UBfEOfEQ%40mail.gmail.com
Author: Michel Pelletier, Alexander Korotkov
Reviewed-by: Justin Pryzby, Mason Sharp, Michael Paquier
2022-07-20 15:49:37 +03:00
Thomas Munro 94ebf8117c Default to dynamic_shared_memory_type=sysv on Solaris.
POSIX shm_open() can sleep for a long time and fail spuriously because
of contention on an internal lock file on Solaris (and presumably
illumos).  Commit 389869af fixed the main problem with this, namely that
we could crash, but it's now clear that "posix" is not a good default.

Therefore, choose "sysv" at initdb time on Solaris and illumos.  Other
choices are still available by editing the postgresql.conf file.

Back-patch only to 15, because contention is much less likely further
back, and it doesn't seem like a good idea to change this in released
branches.  This should clear up the failures on build farm animal
margay.

Discussion: https://postgr.es/m/CA%2BhUKGKqKrCV5xKWfh9rnm%3Do%3DDwZLTLtnsj_XpUi9g5%3DV%2B9oyg%40mail.gmail.com
2022-07-02 16:23:39 +12:00
Peter Eisentraut 9f0b953457 doc: Clean up title case use 2022-06-22 14:24:48 +02:00
Michael Paquier 7bd4a9e990 doc: Do s/int/integer/ to describe the type of some GUC parameters
Three parameters have been using "int" rather than "integer" to describe
their type:
auth_delay.milliseconds
max_logical_replication_workers
pg_prewarm.autoprewarm_interval

This is inconsistent with any other integer GUCs listed in the docs
(148, as far as I can see).

Author: Peter Smith
Discussion: https://postgr.es/m/CAHut+Pv6X5T-veN2abUDUvBxZm+SSm-9otfi3LZPGyOc6u6hiA@mail.gmail.com
2022-06-17 09:03:07 +09:00
Michael Paquier b3fb16e8bb doc: Reword description of roles able to view track_activities's info
The information generated when track_activities is accessible to
superusers, roles with the privileges of pg_read_all_stats, as well as
roles one has the privileges of.  The original text did not outline the
last point, while the change done in ac1ae47 was unclear about the
second point.

Per discussion with Nathan Bossart.

Discussion: https://postgr.es/m/20220521185743.GA886636@nathanxps13
Backpatch-through: 10
2022-05-30 10:50:21 +09:00
Michael Paquier ac1ae477f8 doc: Mention pg_read_all_stats in description of track_activities
The description of track_activities mentioned that it is visible to
superusers and that the information related to the current session can
be seen, without telling about pg_read_all_stats.  Roles that are
granted the privileges of pg_read_all_stats can also see this
information, so mention it in the docs.

Author: Ian Barwick
Reviewed-by: Nathan Bossart
Discussion: https://postgr.es/m/CAB8KJ=jhPyYFu-A5r-ZGP+Ax715mUKsMxAGcEQ9Cx_mBAmrPow@mail.gmail.com
Backpatch-through: 10
2022-05-21 19:05:47 +09:00
Peter Eisentraut 648aa6734f doc: Properly punctuate "etc." 2022-05-19 09:42:17 +02:00
Peter Eisentraut 826be1ffb2 doc: Add links to tables
Formal tables should generally have an xref in the text that points to
them.  Add them here.
2022-04-22 11:19:17 +02:00
David Rowley a59746d311 Docs: wording improvement for compute_query_id = regress
It's more accurate to say that the query identifier is not shown when
compute_query_id = regress rather than to say it is hidden.

This change (ebf6c5249) appeared in v14, so it makes sense to backpatch
this small adjustment to keep the documents consistent between v14 and
master.

Author: Justin Pryzby
Discussion: https://postgr.es/m/20220411020336.GB26620@telsasoft.com
Backpatch-through: 14, where compute_query_id = regress was added
2022-04-13 21:28:25 +12:00
Robert Haas ad385a494f docs: Note the recovery_min_apply_delay bloats pg_wal.
Those WAL files that we're waiting to apply have to be stored
somewhere.

Thom Brown

Discussion: http://postgr.es/m/CAA-aLv4SkJRK6GGcd0Axt8kt6_eWMEbtG7f8NJpFh+rNshtdNA@mail.gmail.com
2022-04-11 10:52:18 -04:00
David Rowley bba3c35b29 Docs: Fix various mistakes and typos
Author: Justin Pryzby
Discussion: https://postgr.es/m/20220411020336.GB26620@telsasoft.com
2022-04-11 20:48:48 +12:00
Andres Freund b3abca6810 pgstat: Update docs to match the shared memory stats reality.
This includes removing documentation for stats_temp_directory, adding
documentation for stats_fetch_consistency, rephrasing references to the stats
collector and documenting that starting a cleanly shut down standby will not
remove stats anymore. The latter point might require further wordsmithing, it
wasn't easy to adjust some of the existing content.

Author: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Author: Andres Freund <andres@anarazel.de>
Reviewed-By: Thomas Munro <thomas.munro@gmail.com>
Reviewed-By: Justin Pryzby <pryzby@telsasoft.com>
Reviewed-By: "David G. Johnston" <david.g.johnston@gmail.com>
Reviewed-By: Lukas Fittl <lukas@fittl.com>
Discussion: https://postgr.es/m/20220303021600.hs34ghqcw6zcokdh@alap3.anarazel.de
2022-04-07 21:35:35 -07:00
Thomas Munro dafae9707a Fix recovery_prefetch docs.
Correct a typo and a couple of sentences that weren't updated to reflect
recent changes to the code.

Reported-by: Justin Pryzby <pryzby@telsasoft.com>
Discussion: https://postgr.es/m/20220407125555.GC24419%40telsasoft.com
2022-04-08 13:43:37 +12:00
Thomas Munro 5dc0418fab Prefetch data referenced by the WAL, take II.
Introduce a new GUC recovery_prefetch.  When enabled, look ahead in the
WAL and try to initiate asynchronous reading of referenced data blocks
that are not yet cached in our buffer pool.  For now, this is done with
posix_fadvise(), which has several caveats.  Since not all OSes have
that system call, "try" is provided so that it can be enabled where
available.  Better mechanisms for asynchronous I/O are possible in later
work.

Set to "try" for now for test coverage.  Default setting to be finalized
before release.

The GUC wal_decode_buffer_size limits the distance we can look ahead in
bytes of decoded data.

The existing GUC maintenance_io_concurrency is used to limit the number
of concurrent I/Os allowed, based on pessimistic heuristics used to
infer that I/Os have begun and completed.  We'll also not look more than
maintenance_io_concurrency * 4 block references ahead.

Reviewed-by: Julien Rouhaud <rjuju123@gmail.com>
Reviewed-by: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Reviewed-by: Alvaro Herrera <alvherre@2ndquadrant.com> (earlier version)
Reviewed-by: Andres Freund <andres@anarazel.de> (earlier version)
Reviewed-by: Justin Pryzby <pryzby@telsasoft.com> (earlier version)
Tested-by: Tomas Vondra <tomas.vondra@2ndquadrant.com> (earlier version)
Tested-by: Jakub Wartak <Jakub.Wartak@tomtom.com> (earlier version)
Tested-by: Dmitry Dolgov <9erthalion6@gmail.com> (earlier version)
Tested-by: Sait Talha Nisanci <Sait.Nisanci@microsoft.com> (earlier version)
Discussion: https://postgr.es/m/CA%2BhUKGJ4VJN8ttxScUFM8dOKX0BrBiboo5uz1cq%3DAovOddfHpA%40mail.gmail.com
2022-04-07 19:42:14 +12:00
Jeff Davis 5c279a6d35 Custom WAL Resource Managers.
Allow extensions to specify a new custom resource manager (rmgr),
which allows specialized WAL. This is meant to be used by a Table
Access Method or Index Access Method.

Prior to this commit, only Generic WAL was available, which offers
support for recovery and physical replication but not logical
replication.

Reviewed-by: Julien Rouhaud, Bharath Rupireddy, Andres Freund
Discussion: https://postgr.es/m/ed1fb2e22d15d3563ae0eb610f7b61bb15999c0a.camel%40j-davis.com
2022-04-06 23:06:46 -07:00
Tom Lane a0ffa885e4 Allow granting SET and ALTER SYSTEM privileges on GUC parameters.
This patch allows "PGC_SUSET" parameters to be set by non-superusers
if they have been explicitly granted the privilege to do so.
The privilege to perform ALTER SYSTEM SET/RESET on a specific parameter
can also be granted.
Such privileges are cluster-wide, not per database.  They are tracked
in a new shared catalog, pg_parameter_acl.

Granting and revoking these new privileges works as one would expect.
One caveat is that PGC_USERSET GUCs are unaffected by the SET privilege
--- one could wish that those were handled by a revocable grant to
PUBLIC, but they are not, because we couldn't make it robust enough
for GUCs defined by extensions.

Mark Dilger, reviewed at various times by Andrew Dunstan, Robert Haas,
Joshua Brindle, and myself

Discussion: https://postgr.es/m/3D691E20-C1D5-4B80-8BA5-6BEB63AF3029@enterprisedb.com
2022-04-06 13:24:33 -04:00
Tomas Vondra db0d67db24 Optimize order of GROUP BY keys
When evaluating a query with a multi-column GROUP BY clause using sort,
the cost may be heavily dependent on the order in which the keys are
compared when building the groups. Grouping does not imply any ordering,
so we're allowed to compare the keys in arbitrary order, and a Hash Agg
leverages this. But for Group Agg, we simply compared keys in the order
as specified in the query. This commit explores alternative ordering of
the keys, trying to find a cheaper one.

In principle, we might generate grouping paths for all permutations of
the keys, and leave the rest to the optimizer. But that might get very
expensive, so we try to pick only a couple interesting orderings based
on both local and global information.

When planning the grouping path, we explore statistics (number of
distinct values, cost of the comparison function) for the keys and
reorder them to minimize comparison costs. Intuitively, it may be better
to perform more expensive comparisons (for complex data types etc.)
last, because maybe the cheaper comparisons will be enough. Similarly,
the higher the cardinality of a key, the lower the probability we’ll
need to compare more keys. The patch generates and costs various
orderings, picking the cheapest ones.

The ordering of group keys may interact with other parts of the query,
some of which may not be known while planning the grouping. E.g. there
may be an explicit ORDER BY clause, or some other ordering-dependent
operation, higher up in the query, and using the same ordering may allow
using either incremental sort or even eliminate the sort entirely.

The patch generates orderings and picks those minimizing the comparison
cost (for various pathkeys), and then adds orderings that might be
useful for operations higher up in the plan (ORDER BY, etc.). Finally,
it always keeps the ordering specified in the query, on the assumption
the user might have additional insights.

This introduces a new GUC enable_group_by_reordering, so that the
optimization may be disabled if needed.

The original patch was proposed by Teodor Sigaev, and later improved and
reworked by Dmitry Dolgov. Reviews by a number of people, including me,
Andrey Lepikhov, Claudio Freire, Ibrar Ahmed and Zhihong Yu.

Author: Dmitry Dolgov, Teodor Sigaev, Tomas Vondra
Reviewed-by: Tomas Vondra, Andrey Lepikhov, Claudio Freire, Ibrar Ahmed, Zhihong Yu
Discussion: https://postgr.es/m/7c79e6a5-8597-74e8-0671-1c39d124c9d6%40sigaev.ru
Discussion: https://postgr.es/m/CA%2Bq6zcW_4o2NC0zutLkOJPsFt80megSpX_dVRo6GK9PC-Jx_Ag%40mail.gmail.com
2022-03-31 01:13:33 +02:00
Daniel Gustafsson 860ea46ba7 doc: Clarify when SSL actually means TLS
SSL has become the de facto term to mean an end-to-end encrypted channel
regardless of protocol used, even though the SSL protocol is deprecated.
Clarify what we mean with SSL in our documentation, especially for new
users who might be looking for TLS.

Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Discussion: https://postgr.es/m/D4ABB281-6CFD-46C6-A4E0-8EC23A2977BC@yesql.se
2022-03-30 13:07:30 +02:00
Tom Lane 0bd7af082a Invent recursive_worktable_factor GUC to replace hard-wired constant.
Up to now, the planner estimated the size of a recursive query's
worktable as 10 times the size of the non-recursive term.  It's hard
to see how to do significantly better than that automatically, but
we can give users control over the multiplier to allow tuning for
specific use-cases.  The default behavior remains the same.

Simon Riggs

Discussion: https://postgr.es/m/CANbhV-EuaLm4H3g0+BSTYHEGxJj3Kht0R+rJ8vT57Dejnh=_nA@mail.gmail.com
2022-03-24 11:47:41 -04:00
Michael Paquier 6bdf1a1400 Fix collection of typos in the code and the documentation
Some words were duplicated while other places were grammatically
incorrect, including one variable name in the code.

Author: Otto Kekalainen, Justin Pryzby
Discussion: https://postgr.es/m/7DDBEFC5-09B6-4325-B942-B563D1A24BDC@amazon.com
2022-03-15 11:29:35 +09:00
Michael Paquier 8e375ea4a0 Bump XLOG_PAGE_MAGIC due to the addition of wal_compression=zstd
While on it, fix a thinko in the docs, introduced by the same commit.

Oversights in e953732.

Reported-by: Justin Pryzby
Discussion: https://postgr.es/m/20220311214900.GN28503@telsasoft.com
2022-03-12 09:39:13 +09:00
Michael Paquier 9198e63996 doc: Standardize capitalization of term "hot standby"/"Hot Standby"
"Hot Standby" was capitalized in a couple of places in the docs, as the
style primarily used when it was introduced, but this has not been much
respected across the years.  Per discussion, it is more natural for the
reader to use "hot standby" (aka lower-case only) when in the middle of
a sentence, and "Hot standby" (aka capitalized) in a title.  This commit
adjusts all the places in the docs to be consistent with this choice,
rather than applying one style or the other midway.

Author: Daniel Westermann
Reviewed-by: Kyotaro Horiguchi, Aleksander Alekseev, Robert Treat
Discussion: https://postgr.es/m/GVAP278MB093160025A779A1A5788D0EAD2039@GVAP278MB0931.CHEP278.PROD.OUTLOOK.COM
2022-03-11 15:16:21 +09:00
Michael Paquier e9537321a7 Add support for zstd with compression of full-page writes in WAL
wal_compression gains a new value, "zstd", to allow the compression of
full-page images using the compression method of the same name.

Compression is done using the default level recommended by the library,
as of ZSTD_CLEVEL_DEFAULT = 3.  Some benchmarking has shown that it
could make sense to use a level lower for the FPI compression, like 1 or
2, as the compression rate did not change much with a bit less CPU
consumed, but any tests done would only cover few scenarios so it is
hard to come to a clear conclusion.  Anyway, there is no reason to not
use the default level instead, which is the level recommended by the
library so it should be fine for most cases.

zstd outclasses easily pglz, and is better than LZ4 where one wants to
have more compression at the cost of extra CPU but both are good enough
in their own scenarios, so the choice between one or the other of these
comes to a study of the workload patterns and the schema involved,
mainly.

This commit relies heavily on 4035cd5, that reshaped the code creating
and restoring full-page writes to be aware of the compression type,
making this integration straight-forward.

This patch borrows some early work from Andrey Borodin, though the patch
got a complete rewrite.

Author: Justin Pryzby
Discussion: https://postgr.es/m/20220222231948.GJ9008@telsasoft.com
2022-03-11 12:18:53 +09:00
Michael Paquier ebf6c5249b Add compute_query_id = regress
"regress" is a new mode added to compute_query_id aimed at facilitating
regression testing when a module computing query IDs is loaded into the
backend, like pg_stat_statements.  It works the same way as "auto",
meaning that query IDs are computed if a module enables it, except that
query IDs are hidden in EXPLAIN outputs to ensure regression output
stability.

Like any GUCs of the kind (force_parallel_mode, etc.), this new
configuration can be added to an instance's postgresql.conf, or just
passed down with PGOPTIONS at command level.  compute_query_id uses an
enum for its set of option values, meaning that this addition ensures
ABI compatibility.

Using this new configuration mode allows installcheck-world to pass when
running the tests on an instance with pg_stat_statements enabled,
stabilizing the test output while checking the paths doing query ID
computations.

Reported-by: Anton Melnikov
Reviewed-by: Julien Rouhaud
Discussion: https://postgr.es/m/1634283396.372373993@f75.i.mail.ru
Discussion: https://postgr.es/m/YgHlxgc/OimuPYhH@paquier.xyz
Backpatch-through: 14
2022-02-22 10:22:15 +09:00
Peter Geoghegan 8f388f6f55 Increase hash_mem_multiplier default to 2.0.
Double the default setting for hash_mem_multiplier, from 1.0 to 2.0.
This setting makes hash-based executor nodes use twice the usual
work_mem limit.

The PostgreSQL 15 release notes should have a compatibility note about
this change.

Author: Peter Geoghegan <pg@bowt.ie>
Discussion: https://postgr.es/m/CAH2-Wzndc_ROk6CY-bC6p9O53q974Y0Ey4WX8jcPbuTZYM4Q3A@mail.gmail.com
2022-02-16 18:41:52 -08:00
Thomas Munro cba5b994c9 Use WL_SOCKET_CLOSED for client_connection_check_interval.
Previously we used poll() directly to check for a POLLRDHUP event.
Instead, use the WaitEventSet API to poll the socket for
WL_SOCKET_CLOSED, which knows how to detect this condition on many more
operating systems.

Reviewed-by: Zhihong Yu <zyu@yugabyte.com>
Reviewed-by: Maksim Milyutin <milyutinma@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/77def86b27e41f0efcba411460e929ae%40postgrespro.ru
2022-02-14 16:52:23 +13:00
Robert Haas 5ef1eefd76 Allow archiving via loadable modules.
Running a shell command for each file to be archived has a lot of
overhead and may not offer as much error checking as you want, or the
exact semantics that you want. So, offer the option to call a loadable
module for each file to be archived, rather than running a shell command.

Also, add a 'basic_archive' contrib module as an example implementation
that archives to a local directory.

Nathan Bossart, with a little bit of kibitzing by me.

Discussion: http://postgr.es/m/20220202224433.GA1036711@nathanxps13
2022-02-03 14:05:02 -05:00
Michael Paquier 410aa248e5 Fix various typos, grammar and code style in comments and docs
This fixes a set of issues that have accumulated over the past months
(or years) in various code areas.  Most fixes are related to some recent
additions, as of the development of v15.

Author: Justin Pryzby
Discussion: https://postgr.es/m/20220124030001.GQ23027@telsasoft.com
2022-01-25 09:40:04 +09:00
Michael Paquier dc686681e0 Introduce log_destination=jsonlog
"jsonlog" is a new value that can be added to log_destination to provide
logs in the JSON format, with its output written to a file, making it
the third type of destination of this kind, after "stderr" and
"csvlog".  The format is convenient to feed logs to other applications.
There is also a plugin external to core that provided this feature using
the hook in elog.c, but this had to overwrite the output of "stderr" to
work, so being able to do both at the same time was not possible.  The
files generated by this log format are suffixed with ".json", and use
the same rotation policies as the other two formats depending on the
backend configuration.

This takes advantage of the refactoring work done previously in ac7c807,
bed6ed3, 8b76f89 and 2d77d83 for the backend parts, and 72b76f7 for the
TAP tests, making the addition of any new file-based format rather
straight-forward.

The documentation is updated to list all the keys and the values that
can exist in this new format.  pg_current_logfile() also required a
refresh for the new option.

Author: Sehrope Sarkuni, Michael Paquier
Reviewed-by: Nathan Bossart, Justin Pryzby
Discussion: https://postgr.es/m/CAH7T-aqswBM6JWe4pDehi1uOiufqe06DJWaU5=X7dDLyqUExHg@mail.gmail.com
2022-01-17 10:16:53 +09:00
Peter Geoghegan 49c9d9fcfa Unify VACUUM VERBOSE and autovacuum logging.
The log_autovacuum_min_duration instrumentation used its own dedicated
code for logging, which was not reused by VACUUM VERBOSE.  This was
highly duplicative, and sometimes led to each code path using slightly
different accounting for essentially the same information.

Clean things up by making VACUUM VERBOSE reuse the same instrumentation
code.  This code restructuring changes the structure of the VACUUM
VERBOSE output itself, but that seems like an overall improvement.  The
most noticeable change in VACUUM VERBOSE output is that it no longer
outputs a distinct message per index per round of index vacuuming.  Most
of the same information (about each index) is now shown in its new
per-operation summary message.  This is far more legible.

A few details are no longer displayed by VACUUM VERBOSE, but that's no
real loss in practice, especially in the common case where we don't need
multiple index scans/rounds of vacuuming.  This super fine-grained
information is still available via DEBUG2 messages, which might still be
useful in debugging scenarios.

VACUUM VERBOSE now shows new instrumentation, which is typically very
useful: all of the log_autovacuum_min_duration instrumentation that it
missed out on before now.  This includes information about WAL overhead,
buffers hit/missed/dirtied information, and I/O timing information.

VACUUM VERBOSE still retains a few INFO messages of its own.  This is
limited to output concerning the progress of heap rel truncation, as
well as some basic information about parallel workers.  These details
are still potentially quite useful.  They aren't a good fit for the log
output, which must summarize the whole operation.

Author: Peter Geoghegan <pg@bowt.ie>
Reviewed-By: Masahiko Sawada <sawada.mshk@gmail.com>
Reviewed-By: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CAH2-WzmW4Me7_qR4X4ka7pxP-jGmn7=Npma_-Z-9Y1eD0MQRLw@mail.gmail.com
2022-01-14 16:50:34 -08:00
Thomas Munro 7170f2159f Allow "in place" tablespaces.
Provide a developer-only GUC allow_in_place_tablespaces, disabled by
default.  When enabled, tablespaces can be created with an empty
LOCATION string, meaning that they should be created as a directory
directly beneath pg_tblspc.  This can be used for new testing scenarios,
in a follow-up patch.  Not intended for end-user usage, since it might
confuse backup tools that expect symlinks.

Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/CA%2BhUKGKpRWQ9SxdxxDmTBCJoR0YnFpMBe7kyzY8SUQk%2BHeskxg%40mail.gmail.com
2022-01-15 00:09:24 +13:00
Robert Haas 64da07c41a Default to log_checkpoints=on, log_autovacuum_min_duration=10m
The idea here is that when a performance problem is known to have
occurred at a certain point in time, it's a good thing if there is
some information available from the logs to help figure out what
might have happened around that time.

This change attracted an above-average amount of dissent, because
it means that a server with default settings will produce some amount
of log output even if nothing has gone wrong. However, by my count,
the mailing list discussion had about twice as many people in favor
of the change as opposed. The reasons for believing that the extra
log output is not an issue in practice are: (1) the rate at which
messages can be generated by this setting is bounded to one every
few minutes on a properly-configured system and (2) production
systems tend to have a lot more junk in the log from that due to
failed connection attempts, ERROR messages generated by application
activity, and the like.

Bharath Rupireddy, reviewed by Fujii Masao and by me. Many other
people commented on the thread, but as far as I can see that was
discussion of the merits of the change rather than review of the
patch.

Discussion: https://postgr.es/m/CALj2ACX-rW_OeDcp4gqrFUAkf1f50Fnh138dmkd0JkvCNQRKGA@mail.gmail.com
2021-12-13 09:48:48 -05:00
Daniel Gustafsson fadac33bb8 Doc: Fix misleading wording of CRL parameters
ssl_crl_file and ssl_crl_dir are both used to for client certificate
revocation, not server certificates.  The description for the params
could be easily misread to mean the opposite however,  as evidenced
by the bugreport leading to this fix.  Similarly, expand sslcrl and
and sslcrldir to explicitly mention server certificates. While there
also mention sslcrldir where previously only sslcrl was discussed.

Backpatch down to v10, with the CRL dir fixes down to 14 where they
were introduced.

Author: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Reviewed-by: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Discussion: https://postgr.es/m/20211202.135441.590555657708629486.horikyota.ntt@gmail.com
Discussion: https://postgr.es/m/CABWY_HCBUCjY1EJHrEGePGEaSZ5b29apgTohCyygtsqe_ySYng@mail.gmail.com
Backpatch-through: 10
2021-12-03 14:15:50 +01:00
Alvaro Herrera 013bb6c8c0
Document units for max_slot_wal_keep_size
The doc blurb failed to mention units, as well as lacking the point
about changeability.

Backpatch to 13.

Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Reported by: b1000101@pm.me
Discussion: https://postgr.es/m/163760291192.26193.10801700492025355788@wrigleys.postgresql.org
2021-11-26 14:31:57 -03:00
Alvaro Herrera e543906e21
Document default and changeability of log_startup_progress_interval
Review for 9ce346eabf.

Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Discussion: https://postgr.es/m/202110292123.bnf6axcp27vx@alvherre.pgsql
2021-11-05 11:31:57 -03:00
Thomas Munro 8781b0ce25 Reject huge_pages=on if shared_memory_type=sysv.
It doesn't work (it could, but hasn't been implemented).
Back-patch to 12, where shared_memory_type arrived.

Reported-by: Alexander Lakhin <exclusion@gmail.com>
Reviewed-by: Alexander Lakhin <exclusion@gmail.com>
Discussion: https://postgr.es/m/163271880203.22789.1125998876173795966@wrigleys.postgresql.org
2021-10-26 12:54:55 +13:00
Robert Haas 9ce346eabf Report progress of startup operations that take a long time.
Users sometimes get concerned whe they start the server and it
emits a few messages and then doesn't emit any more messages for
a long time. Generally, what's happening is either that the
system is taking a long time to apply WAL, or it's taking a
long time to reset unlogged relations, or it's taking a long
time to fsync the data directory, but it's not easy to tell
which is the case.

To fix that, add a new 'log_startup_progress_interval' setting,
by default 10s. When an operation that is known to be potentially
long-running takes more than this amount of time, we'll log a
status update each time this interval elapses.

To avoid undesirable log chatter, don't log anything about WAL
replay when in standby mode.

Nitin Jadhav and Robert Haas, reviewed by Amul Sul, Bharath
Rupireddy, Justin Pryzby, Michael Paquier, and Álvaro Herrera.

Discussion: https://postgr.es/m/CA+TgmoaHQrgDFOBwgY16XCoMtXxsrVGFB2jNCvb7-ubuEe1MGg@mail.gmail.com
Discussion: https://postgr.es/m/CAMm1aWaHF7VE69572_OLQ+MgpT5RUiUDgF1x5RrtkJBLdpRj3Q@mail.gmail.com
2021-10-25 11:51:57 -04:00
Peter Geoghegan 00c61a74bc Doc: normalize vacuum_multixact_failsafe_age ID.
Author: Pavel Luzanov <p.luzanov@postgrespro.ru>
Discussion: https://postgr.es/m/c71a3cfc-a267-3d9f-1b44-fbd668d0ab10@postgrespro.ru
Backpatch: 14-, where the failsafe was introduced.
2021-10-12 10:59:24 -07:00
Michael Paquier 43c1c4f65e Introduce GUC shared_memory_size_in_huge_pages
This runtime-computed GUC shows the number of huge pages required
for the server's main shared memory area, taking advantage of the
work done in 0c39c29 and 0bd305e.  This is useful for users to estimate
the amount of huge pages required for a server as it becomes possible to
do an estimation without having to start the server and potentially
allocate a large chunk of shared memory.

The number of huge pages is calculated based on the existing GUC
huge_page_size if set, or by using the system's default by looking at
/proc/meminfo on Linux.  There is nothing new here as this commit reuses
the existing calculation methods, and just exposes this information
directly to the user.  The routine calculating the huge page size is
refactored to limit the number of files with platform-specific flags.

This new GUC's name was the most popular choice based on the discussion
done.  This is only supported on Linux.

I have taken the time to test the change on Linux, Windows and MacOS,
though for the last two ones large pages are not supported.  The first
one calculates correctly the number of pages depending on the existing
GUC huge_page_size or the system's default.

Thanks to Andres Freund, Robert Haas, Kyotaro Horiguchi, Tom Lane,
Justin Pryzby (and anybody forgotten here) for the discussion.

Author: Nathan Bossart
Discussion: https://postgr.es/m/F2772387-CE0F-46BF-B5F1-CC55516EB885@amazon.com
2021-09-21 10:31:58 +09:00
Michael Paquier bd1788051b Introduce GUC shared_memory_size
This runtime-computed GUC shows the size of the server's main shared
memory area, taking into account the amount of shared memory allocated
by extensions as this is calculated after processing
shared_preload_libraries.

Author: Nathan Bossart
Discussion: https://postgr.es/m/F2772387-CE0F-46BF-B5F1-CC55516EB885@amazon.com
2021-09-08 12:02:30 +09:00
David Rowley deb6ffd4fd Doc: Fix misleading statement about VACUUM memory limits
In ec34040af I added a mention that there was no point in setting
maintenance_work_limit to anything higher than 1GB for vacuum, but that
was incorrect as ginInsertCleanup() also looks at what
maintenance_work_mem is set to during VACUUM and that's not limited to
1GB.

Here I attempt to make it more clear that the limitation is only around
the number of dead tuple identifiers that we can collect during VACUUM.

I've also added a note to autovacuum_work_mem to mention this limitation.
I didn't do that in ec34040af as I'd had some wrong-headed ideas about
just limiting the maximum value for that GUC to 1GB.

Author: David Rowley
Discussion: https://postgr.es/m/CAApHDvpGwOAvunp-E-bN_rbAs3hmxMoasm5pzkYDbf36h73s7w@mail.gmail.com
Backpatch-through: 9.6, same as ec34040af
2021-08-09 16:45:35 +12:00
Tom Lane cf5ce5aa70 Doc: remove bogus <indexterm> items.
Copy-and-pasteo in 665c5855e, evidently.  The 9.6 docs toolchain
whined about duplicate index entries, though our modern toolchain
doesn't.  In any case, these GUCs surely are not about the
default settings of these values.
2021-08-08 15:35:30 -04:00
Peter Geoghegan dd498998a3 Doc: vacuum_multixact_failsafe_age is multixact-based.
Oversight in commit 1e55e7d1, which added a wraparound failsafe
mechanism to VACUUM.

Backpatch: 14-, where VACUUM failsafe was introduced.
2021-07-19 17:20:25 -07:00
Tom Lane 665c5855e5 Doc: document the current-transaction-modes GUCs.
We had documentation of default_transaction_isolation et al,
but for some reason not of transaction_isolation et al.
AFAICS this is just an ancient oversight, so repair.

Per bug #17077 from Yanliang Lei.

Discussion: https://postgr.es/m/17077-ade8e166a01e1374@postgresql.org
2021-07-17 11:52:54 -04:00
Daniel Gustafsson 830ef61bd8 docs: fix inconsistencies in markup and case
Ensure to properly mark up function parameters in text with <parameter>,
avoid using <acronym> for terms which aren't acronyms and properly place
the ", and" in a value list. The acronym removal is a follow-up to commit
fb72a7b8c3 which removed it for minmax-multi.  In passing, also fix an
incorrectly cased word.

Author: Ekaterina Kiryanova <e.kiryanova@postgrespro.ru>
Reviewed-by: Laurenz Albe <laurenz.albe@cybertec.at>
Discussion: https://postgr.es/m/c050ecbc-80b2-b360-3c1d-9fe6a6a11bb5@postgrespro.ru
Backpatch-through: v14
2021-07-15 23:22:58 +02:00
David Rowley 83f4fcc655 Change the name of the Result Cache node to Memoize
"Result Cache" was never a great name for this node, but nobody managed
to come up with another name that anyone liked enough.  That was until
David Johnston mentioned "Node Memoization", which Tom Lane revised to
just "Memoize".  People seem to like "Memoize", so let's do the rename.

Reviewed-by: Justin Pryzby
Discussion: https://postgr.es/m/20210708165145.GG1176@momjian.us
Backpatch-through: 14, where Result Cache was introduced
2021-07-14 12:43:58 +12:00
Tom Lane d68a003912 Rename debug_invalidate_system_caches_always to debug_discard_caches.
The name introduced by commit 4656e3d66 was agreed to be unreasonably
long.  To match this change, rename initdb's recently-added
--clobber-cache option to --discard-caches.

Discussion: https://postgr.es/m/1374320.1625430433@sss.pgh.pa.us
2021-07-13 15:01:01 -04:00
David Rowley ec34040af1 Doc: mention that VACUUM can't utilize over 1GB of RAM
Document that setting maintenance_work_mem to values over 1GB has no
effect on VACUUM.

Reported-by: Martín Marqués
Author: Laurenz Albe
Discussion: https://postgr.es/m/CABeG9LsZ2ozUMcqtqWu_-GiFKB17ih3p8wBHXcpfnHqhCnsc7A%40mail.gmail.com
Backpatch-through: 9.6, oldest supported release
2021-07-04 22:28:38 +12:00
Michael Paquier 4035cd5d4e Add support for LZ4 with compression of full-page writes in WAL
The logic is implemented so as there can be a choice in the compression
used when building a WAL record, and an extra per-record bit is used to
track down if a block is compressed with PGLZ, LZ4 or nothing.

wal_compression, the existing parameter, is changed to an enum with
support for the following backward-compatible values:
- "off", the default, to not use compression.
- "pglz" or "on", to compress FPWs with PGLZ.
- "lz4", the new mode, to compress FPWs with LZ4.

Benchmarking has showed that LZ4 outclasses easily PGLZ.  ZSTD would be
also an interesting choice, but going just with LZ4 for now makes the
patch minimalistic as toast compression is already able to use LZ4, so
there is no need to worry about any build-related needs for this
implementation.

Author: Andrey Borodin, Justin Pryzby
Reviewed-by: Dilip Kumar, Michael Paquier
Discussion: https://postgr.es/m/3037310D-ECB7-4BF1-AF20-01C10BB33A33@yandex-team.ru
2021-06-29 11:17:55 +09:00
Thomas Munro 34a8b64b4e Change recovery_init_sync_method to PGC_SIGHUP.
The setting has no effect except during startup.  It's still nice to be
able to change it dynamically, which is expected to be pretty useful to
an admin following crash recovery when restarting the cluster is not so
appealing.

Per discussions following commits 2941138e6 and 61752afb2.

Author: Justin Pryzby <pryzby@telsasoft.com>
Reviewed-by: Fujii Masao <masao.fujii@oss.nttdata.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Thomas Munro <thomas.munro@gmail.com>
Discussion: https://postgr.es/m/20210529192321.GM2082%40telsasoft.com
2021-06-28 15:30:39 +12:00
Michael Paquier 15ff5401d1 doc: Add acronyms for MITM and SNI
This adds MITM and SNI as acronyms, as the documentation already had
them marked up with <acronym>.

While on it, make sure to spell man-in-the-middle with dashes
consistently, and add acronyms for those new terms where appropriate.

Author: Daniel Gustafsson
Reviewed-by: Michael Paquier
Discussion: https://postgr.es/m/CE12DD5C-4BB3-4166-BC9A-39779568734C@yesql.se
2021-06-25 11:29:03 +09:00
Michael Paquier 797b0fc0b0 doc: Move remove_temp_files_after_crash to section for developer options
The main goal of this option is to allow inspecting temporary files for
debugging purposes, so moving the parameter there is natural.

Oversight in cd91de0.

Reported-by: Justin Pryzby
Author: Euler Taveira
Discussion: https://postgr.es/m/20210612004347.GP16435@telsasoft.com
2021-06-25 08:40:16 +09:00
Michael Paquier f80979f659 doc: Apply markup <productname> to OpenSSL more consistently
Author: Daniel Gustafsson
Discussion: https://postgr.es/m/CE12DD5C-4BB3-4166-BC9A-39779568734C@yesql.se
2021-06-18 14:22:31 +09:00
David Rowley 04539e73fa Use the correct article for abbreviations
We've accumulated quite a mix of instances of "an SQL" and "a SQL" in the
documents.  It would be good to be a bit more consistent with these.

The most recent version of the SQL standard I looked at seems to prefer
"an SQL".  That seems like a good lead to follow, so here we change all
instances of "a SQL" to become "an SQL".  Most instances correctly use
"an SQL" already, so it also makes sense to use the dominant variation in
order to minimise churn.

Additionally, there were some other abbreviations that needed to be
adjusted. FSM, SSPI, SRF and a few others.  Also fix some pronounceable,
abbreviations to use "a" instead of "an".  For example, "a SASL" instead
of "an SASL".

Here I've only adjusted the documents and error messages.  Many others
still exist in source code comments.  Translator hint comments seem to be
the biggest culprit.  It currently does not seem worth the churn to change
these.

Discussion: https://postgr.es/m/CAApHDvpML27UqFXnrYO1MJddsKVMQoiZisPvsAGhKE_tsKXquw%40mail.gmail.com
2021-06-11 13:38:04 +12:00
Tom Lane ba356a397d Doc: improve libpq service-file docs, avoid overspecifying pathnames.
Clarify libpq.sgml's description of service file locations and
semantics.  Avoid use of backtick'ed pg_config calls to describe
paths; that doesn't work on Windows, and even on Unix it's an
idiom that not all readers may be instantly familiar with.

Don't overspecify the locations of include files, instead writing
only as much as you'd use in #include directives.  The previous text
in these places was incorrect for some installations, depending on
where "postgresql" is in the install path.

Our convention for referencing the user's home directory seems
to be "~", so change the one place that spelled it "$HOME".

install-windows.sgml follows the platform convention of spelling
file paths with "\", so change the one place that used "/".

Haiying Tang and Tom Lane

Discussion: https://postgr.es/m/162149020918.26174.7150424047314144297@wrigleys.postgresql.org
2021-05-29 14:27:37 -04:00
Tom Lane e6241d8e03 Rethink definition of pg_attribute.attcompression.
Redefine '\0' (InvalidCompressionMethod) as meaning "if we need to
compress, use the current setting of default_toast_compression".
This allows '\0' to be a suitable default choice regardless of
datatype, greatly simplifying code paths that initialize tupledescs
and the like.  It seems like a more user-friendly approach as well,
because now the default compression choice doesn't migrate into table
definitions, meaning that changing default_toast_compression is
usually sufficient to flip an installation's behavior; one needn't
tediously issue per-column ALTER SET COMPRESSION commands.

Along the way, fix a few minor bugs and documentation issues
with the per-column-compression feature.  Adopt more robust
APIs for SetIndexStorageProperties and GetAttributeCompression.

Bump catversion because typical contents of attcompression will now
be different.  We could get away without doing that, but it seems
better to ensure v14 installations all agree on this.  (We already
forced initdb for beta2, anyway.)

Discussion: https://postgr.es/m/626613.1621787110@sss.pgh.pa.us
2021-05-27 13:24:27 -04:00
Michael Paquier 2941138e60 doc: Fix description of some GUCs in docs and postgresql.conf.sample
The following parameters have been imprecise, or incorrect, about their
description (PGC_POSTMASTER or PGC_SIGHUP):
- autovacuum_work_mem (docs, as of 9.6~)
- huge_page_size (docs, as of 14~)
- max_logical_replication_workers (docs, as of 10~)
- max_sync_workers_per_subscription (docs, as of 10~)
- min_dynamic_shared_memory (docs, as of 14~)
- recovery_init_sync_method (postgresql.conf.sample, as of 14~)
- remove_temp_files_after_crash (docs, as of 14~)
- restart_after_crash (docs, as of 9.6~)
- ssl_min_protocol_version (docs, as of 12~)
- ssl_max_protocol_version (docs, as of 12~)

This commit adjusts the description of all these parameters to be more
consistent with the practice used for the others.

Revewed-by: Justin Pryzby
Discussion: https://postgr.es/m/YK2ltuLpe+FbRXzA@paquier.xyz
Backpatch-through: 9.6
2021-05-27 14:57:28 +09:00
Alvaro Herrera cafde58b33
Allow compute_query_id to be set to 'auto' and make it default
Allowing only on/off meant that all either all existing configuration
guides would become obsolete if we disabled it by default, or that we
would have to accept a performance loss in the default config if we
enabled it by default.  By allowing 'auto' as a middle ground, the
performance cost is only paid by those who enable pg_stat_statements and
similar modules.

I only edited the release notes to comment-out a paragraph that is now
factually wrong; further edits are probably needed to describe the
related change in more detail.

Author: Julien Rouhaud <rjuju123@gmail.com>
Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>
Discussion: https://postgr.es/m/20210513002623.eugftm4nk2lvvks3@nol
2021-05-15 14:13:09 -04:00
Thomas Munro c2dc19342e Revert recovery prefetching feature.
This set of commits has some bugs with known fixes, but at this late
stage in the release cycle it seems best to revert and resubmit next
time, along with some new automated test coverage for this whole area.

Commits reverted:

dc88460c: Doc: Review for "Optionally prefetch referenced data in recovery."
1d257577: Optionally prefetch referenced data in recovery.
f003d9f8: Add circular WAL decoding buffer.
323cbe7c: Remove read_page callback from XLogReader.

Remove the new GUC group WAL_RECOVERY recently added by a55a9847, as the
corresponding section of config.sgml is now reverted.

Discussion: https://postgr.es/m/CAOuzzgrn7iKnFRsB4MHp3UisEQAGgZMbk_ViTN4HV4-Ksq8zCg%40mail.gmail.com
2021-05-10 16:06:09 +12:00
Michael Paquier 02a93e7ef9 doc: Fix some gaps with the documentation related to LZ4
The upstream project is officially named "LZ4", and the documentation
was confused with the option value that can be used with DDLs supporting
this option, and the project name.

Documentation related to the configure option --with-lz4 was missing, so
add something for that.

Author: Dilip Kumar, Michael Paquier
Reviewed-by: Justin Pryzby
Discussion: https://postgr.es/m/YJaOZQDXBVySq+Cc@paquier.xyz
2021-05-10 09:32:56 +09:00
Tom Lane f9b809e7fb Doc: copy-editing for debug_invalidate_system_caches_always description.
I came to fix "useful only useful", but the more I looked at the text
the more things I thought could be improved.
2021-05-08 11:33:13 -04:00
Alvaro Herrera 94b9cb7225
Improve documentation for default_tablespace on partitioned tables
Backpatch to 12, where 87259588d0 introduced the current behavior.

Per note from Justin Pryzby.

Co-authored-by: Justin Pryzby <pryzby@telsasoft.com>
Discussion: https://postgr.es/m/20210416143135.GI3315@telsasoft.com
2021-04-29 11:31:24 -04:00
Michael Paquier 1599e7b375 doc: Move parallel_leader_participation to its correct category
parallel_leader_participation got introduced in e5253fd, where it was
listed under RESOURCES_ASYNCHRONOUS in guc.c, but the documentation
did not reflect that and listed it with the other planner-related
options.  This commit fixes this inconsistency as the parameter is
intended to be an asynchronous one.

While on it, reorganize a bit the section dedicated to asynchronous
parameters, backend_flush_after being moved first to do better in terms
of alphabetical order of the options listed.

Reported-by: Yanliang Lei
Author: Bharath Rupireddy
Discussion: https://postgr.es/m/16972-42d4b0c15aa1d5f5@postgresql.org
2021-04-22 09:47:43 +09:00