"\if :{?variable_name}" will be translated to "\if TRUE" if the variable
exists and "\if FALSE" otherwise. Thus it will be possible to execute code
conditionally on the existence of the variable, regardless of its value.

Fabien Coelho, with some review by Robins Tharakan and some light text
editing by me.

Discussion: https://postgr.es/m/alpine.DEB.2.20.1708260835520.3627@lancre

Previously, the code didn't think about this case and would just try to
analyze such a column twice.  That would fail at the point of inserting
the second version of the pg_statistic row, with obscure error messsages
like "duplicate key value violates unique constraint" or "tuple already
updated by self", depending on context and PG version.  We could allow
the case by ignoring duplicate column specifications, but it seems better
to reject it explicitly.

The bogus error messages seem like arguably a bug, so back-patch to
all supported versions.

Nathan Bossart, per a report from Michael Paquier, and whacked
around a bit by me.

Discussion: https://postgr.es/m/E061A8E3-5E3D-494D-94F0-E8A9B312BBFC@amazon.com

These variables are only ever written to in assertion-enabled builds,
and the latest Microsoft compilers complain about such variables in
non-assertion-enabled builds.

Apparently they don't worry so much about variables that are written to
but not read from, so most of our PG_USED_FOR_ASSERTS_ONLY variables
don't cause the problem.

Discussion: https://postgr.es/m/7800.1505950322@sss.pgh.pa.us

This is not used for anything yet, but it is necessary infrastructure
for partition-wise join and for partition pruning without constraint
exclusion.

Ashutosh Bapat, reviewed by Amit Langote and with quite a few changes,
mostly cosmetic, by me.  Additional review and testing of this patch
series by Antonin Houska, Amit Khandekar, Rafia Sabih, Rajkumar
Raghuwanshi, Thomas Munro, and Dilip Kumar.

Discussion: http://postgr.es/m/CAFjFpRfneFG3H+F6BaiXemMrKF+FY-POpx3Ocy+RiH3yBmXSNw@mail.gmail.com

pg_newlocale_from_collation() used malloc() and strdup() directly,
which is generally not per backend coding style, and it didn't bother
to check for failure results, but would just SIGSEGV instead.  Also,
if one of the numerous error checks in the middle of the function
failed, the already-allocated memory would be leaked permanently.
Admittedly, it's not a lot of memory, but it could build up if this
function were called repeatedly for a bad collation.

The first two problems are easily cured by palloc'ing in TopMemoryContext
instead of calling libc directly.  We can fairly easily dodge the leakage
problem for the struct pg_locale_struct by filling in a temporary variable
and allocating permanent storage only once we reach the bottom of the
function.  It's harder to get rid of the potential leakage for ICU's copy
of the collcollate string, but at least that's only allocated after most
of the error checks; so live with that aspect.

Back-patch to v10 where this code came in, with one or another of the
ICU patches.

005_encoding.pl neglected to wait for the subscriber's initial
synchronization to happen.  While we have not seen this fail in
the buildfarm, it's pretty easy to demonstrate there's an issue
by hacking logicalrep_worker_launch() to fail most of the time.

Michael Paquier

Discussion: https://postgr.es/m/27032.1505749806@sss.pgh.pa.us

GRANT, REVOKE, and some allied commands allow the noise word GROUP
before a role name (cf. grantee production in gram.y).  This option
does not exist elsewhere, but it had nonetheless snuck into the
documentation for ALTER ROLE, ALTER USER, and CREATE SCHEMA.

Seems to be a copy-and-pasteo in commit 31eae602, which did expand the
syntax choices here, but not in that way.  Back-patch to 9.5 where that
came in.

Discussion: https://postgr.es/m/20170916123750.8885.66941@wrigleys.postgresql.org

Commit 0a480502 broke it.

Report by Andreas Seltenreich.  Fix by Ashutosh Bapat.

Discussion: http://postgr.es/m/874ls2vrnx.fsf@ansel.ydns.eu

Thomas Munro

Discussion: http://postgr.es/m/CAEepm=2j-HAgnBUrAazwS0ry7Z_ihk+d7g+Ye3u99+6WbiGt_Q@mail.gmail.com

This step was erroneously removed four days ago by me.

Reported-by: Magnus via IM

Backpatch-through: 9.5

from gcc-7 -Wformat-truncation (via -Wall)

Remove gratuitous differences in the process names shown in
pg_stat_activity.backend_type and the ps output.
Reviewed-by: Takayuki Tsunakawa <tsunakawa.takay@jp.fujitsu.com>

Since rsync 3.0.0 (released in 2008), the default way to enumerate
changes was changed in a way that makes it less likely that the hardlink
sync mode works. Since the whole point of the documented procedure is
for the hardlinks to work, change our docs to suggest using the
backwards compatibility switch.

For performance reasons a larger segment size than the default 16MB
can be useful. A larger segment size has two main benefits: Firstly,
in setups using archiving, it makes it easier to write scripts that
can keep up with higher amounts of WAL, secondly, the WAL has to be
written and synced to disk less frequently.

But at the same time large segment size are disadvantageous for
smaller databases. So far the segment size had to be configured at
compile time, often making it unrealistic to choose one fitting to a
particularly load. Therefore change it to a initdb time setting.

This includes a breaking changes to the xlogreader.h API, which now
requires the current segment size to be configured.  For that and
similar reasons a number of binaries had to be taught how to recognize
the current segment size.

Author: Beena Emerson, editorialized by Andres Freund
Reviewed-By: Andres Freund, David Steele, Kuntal Ghosh, Michael
    Paquier, Peter Eisentraut, Robert Hass, Tushar Ahuja
Discussion: https://postgr.es/m/CAOG9ApEAcQ--1ieKbhFzXSQPw_YLmepaa4hNdnY5+ZULpt81Mw@mail.gmail.com

As it turns out we can't rely that the script's monitoring session is
terminated with a proper error by the server, because the session
might be terminated while already trying to send data.

Also improve robustness and error reporting facilities of the test,
developed while debugging this issue.

Discussion: https://postgr.es/m/20170920020038.kllxgilo7xzwmtto@alap3.anarazel.de

The preceding patch allowed us to remove useless GiST support functions.
This patch actually does that for all the no-op cases in the core GiST
code.  This buys us whatever performance gain is to be had, and more
importantly exercises the preceding patch.

There remain no-op functions in the contrib GiST opclasses, but those
will take more work to remove.

Discussion: https://postgr.es/m/CAJEAwVELVx9gYscpE=Be6iJxvdW5unZ_LkcAaVNSeOwvdwtD=A@mail.gmail.com

There are common use-cases in which the compress and/or decompress
functions can be omitted, with the result being that we make no
data transformation when storing or retrieving index values.
Previously, you had to provide a no-op function anyway, but this
patch allows such opclass support functions to be omitted.

Furthermore, if the compress function is omitted, then the core code
knows that the stored representation is the same as the original data.
This means we can allow index-only scans without requiring a fetch
function to be provided either.  Previously you had to provide a
no-op fetch function if you wanted IOS to work.

This reportedly provides a small performance benefit in such cases,
but IMO the real reason for doing it is just to reduce the amount of
useless boilerplate code that has to be written for GiST opclasses.

Andrey Borodin, reviewed by Dmitriy Sarafannikov

Discussion: https://postgr.es/m/CAJEAwVELVx9gYscpE=Be6iJxvdW5unZ_LkcAaVNSeOwvdwtD=A@mail.gmail.com

Reported-By: Robert Haas
Discussion: https://postgr.es/m/CA+Tgmoa+YBvWgFST2NVoeXjVSohEpK=vqnVCsoCkhTVVxfLcVQ@mail.gmail.com

The plan is to convert the current pg_upgrade test to the TAP
framework.  This commit just puts a basic TAP test in place so that we
can see how the build farm behaves, since the build farm client has some
special knowledge of the pg_upgrade tests.

Author: Michael Paquier <michael.paquier@gmail.com>

The use of strnlen rather than strlen was just paranoia. Instead of
giving up on the paranoia, just implement the safeguard
differently. And add a comment explaining why we're careful.

Author: Andres Freund
Discussion: https://postgr.es/m/E1duOkJ-0001Mc-U5@gemulon.postgresql.org

Previously multi-byte aware truncation was done on every
pgstat_report_activity() call - proving to be a bottleneck for
workloads with long query strings that execute quickly.

Instead move the truncation to the read side, which commonly is
executed far less frequently. That's possible because all server
encodings allow to determine the length of a multi-byte string from
the first byte.

Rename PgBackendStatus.st_activity to st_activity_raw so existing
extension users of the field break - their code has to be adjusted to
use pgstat_clip_activity().

Author: Andres Freund
Tested-By: Khuntal Ghosh
Reviewed-By: Robert Haas, Tom Lane
Discussion: https://postgr.es/m/20170912071948.pa7igbpkkkviecpz@alap3.anarazel.de

This reverts commit 890faaf1 which attempted unsuccessfully to deal with
the problem, and instead just comments out these tests like other similar
tests elsewhere in the script.

Testing indicates this can save a third to a half of the runtime
of the function.

Pavel Stehule, reviewed by Alexander Kuzmenkov

Discussion: https://postgr.es/m/CAFj8pRAT62pRgjoHbgTfJUc2uLmeQ4saUj+yVJAEZUiMwNCmdg@mail.gmail.com

Problem introduced with non-ascii characters in commit f2464997
and discovered on various buildfarm animals.

Add timeouts in case psql doesn't deliver the expected output, and try
to cause the monitoring psql to be fully connected to a backend.  This
isn't necessarily everything needed, but at least the timeouts should
reduce the pain for buildfarm owners.

Author: Andres Freund
Reported-By: Tom Lane, BF animals prairiedog and calliphoridae
Discussion: https://postgr.es/m/E1du6ZT-00043I-91@gemulon.postgresql.org

Reported-by: Zhou Digoal

Discussion: https://postgr.es/m/20170912133722.25637.91@wrigleys.postgresql.org

Backpatch-through: 10

This is similar to text_pattern_ops.

Alexey Chernyshov, reviewed by Jacob Champion.

Previously statement_timeout, in the extended protocol, affected all
messages till a Sync message.  For clients that pipeline/batch query
execution that's problematic.

Instead disable timeout after each Execute message, and enable, if
necessary, the timer in start_xact_command(). As that's done only for
Execute and not Parse / Bind, pipelining the latter two could still
cause undesirable timeouts. But a survey of protocol implementations
shows that all drivers issue Sync messages when preparing, and adding
timeout rearming to both is fairly expensive for the common parse /
bind / execute sequence.

Author: Tatsuo Ishii, editorialized by Andres Freund
Reviewed-By: Takayuki Tsunakawa, Andres Freund
Discussion: https://postgr.es/m/20170222.115044.1665674502985097185.t-ishii@sraoss.co.jp

A bugfix for commit 8c0d7baf.  The code
would have crashed if hashtable->size_log2 ever had the same value as
hashtable->control->size_log2 by coincidence.

Per Valgrind.

Author: Thomas Munro
Reported-By: Tomas Vondra
Discussion: https://postgr.es/m/e72fb33c-4f31-f276-e972-263d9b59554d%402ndquadrant.com

Given that I managed to break this...  We probably should extend the
tests to also cover other sub-processes dying, but that's something
for later.

Author: Andres Freund
Discussion: https://postgr.es/m/20170917080752.rcmihzfmgbeuqjk2@alap3.anarazel.de

The bug was caused by not re-reading the control file during crash
recovery restarts, which lead to an attempt to pfree() shared memory
contents. The fix is to re-read the control file, which seems good
anyway.

It's unclear as of this moment, whether we want to keep the
refactoring introduced in the commit referenced above, or come up with
an alternative approach. But fixing the bug in the mean time seems
like a good idea regardless.

A followup commit will introduce regression test coverage for crash
restarts.

Reported-By: Tom Lane
Discussion: https://postgr.es/m/14134.1505572349@sss.pgh.pa.us

Make the btree page-flags test macros (P_ISLEAF and friends) return clean
boolean values, rather than values that might not fit in a bool.  Use them
in a few places that were randomly referencing the flag bits directly.

In passing, change access/nbtree/'s only direct use of BUFFER_LOCK_SHARE to
BT_READ.  (Some think we should go the other way, but as long as we have
BT_READ/BT_WRITE, let's use them consistently.)

Masahiko Sawada, reviewed by Doug Doole

Discussion: https://postgr.es/m/CAD21AoBmWPeN=WBB5Jvyz_Nt3rmW1ebUyAnk3ZbJP3RMXALJog@mail.gmail.com

Extensions with custom plan nodes might like to use these in their
EXPLAIN output.

Hadi Moshayedi

Discussion: https://postgr.es/m/CA+_kT_dU-rHCN0u6pjA6bN5CZniMfD=-wVqPY4QLrKUY_uJq5w@mail.gmail.com

By project convention, these names should include "P" when dealing with a
pointer type; that is, if the result of a GETARG macro is of type FOO *,
it should be called PG_GETARG_FOO_P not just PG_GETARG_FOO.  Some newer
types such as JSONB and ranges had not followed the convention, and a
number of contrib modules hadn't gotten that memo either.  Rename the
offending macros to improve consistency.

In passing, fix a few places that thought PG_DETOAST_DATUM() returns
a Datum; it does not, it returns "struct varlena *".  Applying
DatumGetPointer to that happens not to cause any bad effects today,
but it's formally wrong.  Also, adjust an ltree macro that was designed
without any thought for what pgindent would do with it.

This is all cosmetic and shouldn't have any impact on generated code.

Mark Dilger, some further tweaks by me

Discussion: https://postgr.es/m/EA5676F4-766F-4F38-8348-ECC7DB427C6A@gmail.com

If we failed to get a background worker slot, the code just walked
away from the logicalrep-worker slot it already had, leaving that
looking like the worker is still starting up.  This led to an indefinite
hang in subscription startup, as reported by Thomas Munro.  We must
release the slot on failure.

Also fix a thinko: we must capture the worker slot's generation before
releasing LogicalRepWorkerLock the first time, else testing to see if
it's changed is pretty meaningless.

BTW, the CHECK_FOR_INTERRUPTS() in WaitForReplicationWorkerAttach is a
ticking time bomb, even without considering the possibility of elog(ERROR)
in one of the other functions it calls.  Really, this entire business needs
a redesign with some actual thought about error recovery.  But for now
I'm just band-aiding the case observed in testing.

Back-patch to v10 where this code was added.

Discussion: https://postgr.es/m/CAEepm=2bP3TBMFBArP6o20AZaRduWjMnjCjt22hSdnA-EvrtCw@mail.gmail.com

When ALTER SUBSCRIPTION DISABLE is run in the same transaction before
DROP SUBSCRIPTION, the latter will hang because workers will still be
running, not having seen the DISABLE committed, and DROP SUBSCRIPTION
will wait until the workers have vacated the replication origin slots.

Previously, DROP SUBSCRIPTION killed the logical replication workers
immediately only if it was going to drop the replication slot, otherwise
it scheduled the worker killing for the end of the transaction, as a
result of 7e174fa7.  This, however,
causes the present problem.  To fix, kill the workers immediately in all
cases.  This covers all cases: A subscription that doesn't have a
replication slot must be disabled.  It was either disabled in the same
transaction, or it was already disabled before the current transaction,
but then there shouldn't be any workers left and this won't make a
difference.
Reported-by: Arseny Sher <a.sher@postgrespro.ru>
Discussion: https://www.postgresql.org/message-id/flat/87mv6av84w.fsf%40ars-thinkpad

Add item about number of times statement-level triggers will be fired.
Rearrange the compatibility items into (what seems to me) a less
random ordering.

This lets it do the right thing for, eg, varchar columns.
Back-patch to 9.5 where this logic appeared.

David Rowley, per report from Kim Rose Carlsen

Discussion: https://postgr.es/m/VI1PR05MB17091F9A9876528055D6A827C76D0@VI1PR05MB1709.eurprd05.prod.outlook.com