As of Windows 10 version 1803, Unix-domain sockets are supported on
Windows.  But it's not automatically detected by configure because it
looks for struct sockaddr_un and Windows doesn't define that.  So we
just make our own definition on Windows and override the configure
result.

Set DEFAULT_PGSOCKET_DIR to empty on Windows so by default no
Unix-domain socket is used, because there is no good standard
location.

In pg_upgrade, we have to do some extra tweaking to preserve the
existing behavior of not using Unix-domain sockets on Windows.  Adding
support would be desirable, but it needs further work, in particular a
way to select whether to use Unix-domain sockets from the command-line
or with a run-time test.

The pg_upgrade test script needs a fix.  The previous code passed
"localhost" to postgres -k, which only happened to work because
Windows used to ignore the -k argument value altogether.  We instead
need to pass an empty string to get the desired effect.

The test suites will continue to not use Unix-domain sockets on
Windows.  This requires a small tweak in pg_regress.c.  The TAP tests
don't need to be changed because they decide by the operating system
rather than HAVE_UNIX_SOCKETS.
Reviewed-by: Andrew Dunstan <andrew.dunstan@2ndquadrant.com>
Discussion: https://www.postgresql.org/message-id/flat/54bde68c-d134-4eb8-5bd3-8af33b72a010@2ndquadrant.com

Formerly we applied a functional dependency "a => b with dependency
degree f" using the formula

  P(a,b) = P(a) * [f + (1-f)*P(b)]

This leads to the possibility that the combined selectivity P(a,b)
could exceed P(b), which is not ideal. The addition of support for IN
and OR clauses (commits 8f321bd1 and ccaa3569) would seem to make
this more likely, since the user-supplied values in such clauses are
not necessarily compatible with the functional dependency.

Mitigate this by using the formula

  P(a,b) = f * Min(P(a), P(b)) + (1-f) * P(a) * P(b)

instead, which guarantees that the combined selectivity is less than
each column's individual selectivity. Logically, this is modifies the
part of the formula that accounts for dependent rows to handle cases
where P(a) > P(b), whilst not changing the second term which accounts
for independent rows.

Additionally, this refactors the way that functional dependencies are
applied, so now dependencies_clauselist_selectivity() estimates both
the implying clauses and the implied clauses for each functional
dependency (formerly only the implied clauses were estimated), and now
all clauses for each attribute are taken into account (formerly only
one clause for each implied attribute was estimated). This removes the
previously built-in assumption that only equality clauses will be
seen, which is no longer true, and opens up the possibility of
applying functional dependencies to more general clauses.

Patch by me, reviewed by Tomas Vondra.

Discussion: https://postgr.es/m/CAEZATCXaNFZyOhR4XXAfkvj1tibRBEjje6ZbXwqWUB_tqbH%3Drw%40mail.gmail.com
Discussion: https://postgr.es/m/20200318002946.6dvblukm3cfmgir2%40development

Feature C011 was still listed in sql_feature_packages.txt but had been
removed from sql_features.txt, so also remove from the former.

Traditionally autovacuum has only ever invoked a worker based on the
estimated number of dead tuples in a table and for anti-wraparound
purposes. For the latter, with certain classes of tables such as
insert-only tables, anti-wraparound vacuums could be the first vacuum that
the table ever receives. This could often lead to autovacuum workers being
busy for extended periods of time due to having to potentially freeze
every page in the table. This could be particularly bad for very large
tables. New clusters, or recently pg_restored clusters could suffer even
more as many large tables may have the same relfrozenxid, which could
result in large numbers of tables requiring an anti-wraparound vacuum all
at once.

Here we aim to reduce the work required by anti-wraparound and aggressive
vacuums in general, by triggering autovacuum when the table has received
enough INSERTs. This is controlled by adding two new GUCs and reloptions;
autovacuum_vacuum_insert_threshold and
autovacuum_vacuum_insert_scale_factor. These work exactly the same as the
existing scale factor and threshold controls, only base themselves off the
number of inserts since the last vacuum, rather than the number of dead
tuples. New controls were added rather than reusing the existing
controls, to allow these new vacuums to be tuned independently and perhaps
even completely disabled altogether, which can be done by setting
autovacuum_vacuum_insert_threshold to -1.

We make no attempt to skip index cleanup operations on these vacuums as
they may trigger for an insert-mostly table which continually doesn't have
enough dead tuples to trigger an autovacuum for the purpose of removing
those dead tuples. If we were to skip cleaning the indexes in this case,
then it is possible for the index(es) to become bloated over time.

There are additional benefits to triggering autovacuums based on inserts,
as tables which never contain enough dead tuples to trigger an autovacuum
are now more likely to receive a vacuum, which can mark more of the table
as "allvisible" and encourage the query planner to make use of Index Only
Scans.

Currently, we still obey vacuum_freeze_min_age when triggering these new
autovacuums based on INSERTs. For large insert-only tables, it may be
beneficial to lower the table's autovacuum_freeze_min_age so that tuples
are eligible to be frozen sooner. Here we've opted not to zero that for
these types of vacuums, since the table may just be insert-mostly and we
may otherwise freeze tuples that are still destined to be updated or
removed in the near future.

There was some debate to what exactly the new scale factor and threshold
should default to. For now, these are set to 0.2 and 1000, respectively.
There may be some motivation to adjust these before the release.

Author: Laurenz Albe, Darafei Praliaskouski
Reviewed-by: Alvaro Herrera, Masahiko Sawada, Chris Travers, Andres Freund, Justin Pryzby
Discussion: https://postgr.es/m/CAC8Q8t%2Bj36G_bLF%3D%2B0iMo6jGNWnLnWb1tujXuJr-%2Bx8ZCCTqoQ%40mail.gmail.com

Delaying unlocking the right child page until after the point that the
left child's parent page has been refound is no longer truly necessary.
Commit 40dae7ec made nbtree tolerant of interrupted page splits.  VACUUM
was taught to avoid deleting a page that happens to be the right half of
an incomplete split.  As long as page splits don't unlock the left child
page until the end of the second/final phase, it should be safe to
unlock the right child page earlier (at the end of the first phase).

It probably isn't actually useful to release the right child's lock
earlier like this (it probably won't improve performance).  Even still,
pointing out that it ought to be safe to do so should make it easier to
understand the overall design.

The parameters primary_conninfo, primary_slot_name and
wal_receiver_create_temp_slot can now be changed with a simple "reload"
signal, no longer requiring a server restart.  This is achieved by
signalling the walreceiver process to terminate and having it start
again with the new values.

Thanks to Andres Freund, Kyotaro Horiguchi, Fujii Masao for discussion.

Author: Sergei Kornilov <sk@zsrv.org>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://postgr.es/m/19513901543181143@sas1-19a94364928d.qloud-c.yandex.net

Commit 32973082 gave walreceiver the ability to create and use a
temporary replication slot, and made it controllable by a GUC (enabled
by default) that can be changed with SIGHUP.  That's useful but has two
problems: one, it's possible to cause the origin server to fill its disk
if the slot doesn't advance in time; and also there's a disconnect
between state passed down via the startup process and GUCs that
walreceiver reads directly.

We handle the first problem by setting the option to disabled by
default.  If the user enables it, its on their head to make sure that
disk doesn't fill up.

We handle the second problem by passing the flag via startup rather than
having walreceiver acquire it directly, and making it PGC_POSTMASTER
(which ensures a walreceiver always has the fresh value).  A future
commit can relax this (to PGC_SIGHUP again) by having the startup
process signal walreceiver to shutdown whenever the value changes.

Author: Sergei Kornilov <sk@zsrv.org>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://postgr.es/m/20200122055510.GH174860@paquier.xyz

Buildfarm experience shows what probably should've occurred to me before:
if a cache flush occurs partway through building a generic plan, then
the plansource may have is_valid = false even though the plan is valid.
We need to accept this case, use the generated plan, and then try to
replan the next time.  We can't try to replan immediately, because that
would produce an infinite loop in CLOBBER_CACHE_ALWAYS builds; moreover
it's really overkill.  (We can assume that the plan is valid, it's just
possibly a bit stale.  Note that the pre-existing code behaved this way,
and the non-simple-expression code paths do too.)  Conversely, not using
the generated plan would drop us into the not-a-simple-expression code
path, which is bad for performance and would also cause regression-test
failures due to visibly different error-reporting behavior.

Hence, refactor the validity-check functions so that the initial check
and recheck cases can react differently to plansource->is_valid.
This makes their usage a bit simpler, too.

Discussion: https://postgr.es/m/7072.1585332104@sss.pgh.pa.us

Change F311 to supported.  This was already accomplished when
subfeature F311-04 (WITH CHECK OPTION) was added, but the top-level
feature wasn't updated at the time.

For relatively simple expressions (say, "x + 1" or "x > 0"), plpgsql's
management overhead exceeds the cost of evaluating the expression.
This patch substantially improves that situation, providing roughly
2X speedup for such trivial expressions.

First, add infrastructure in the plancache to allow fast re-validation
of cached plans that contain no table access, and hence need no locks.
Teach plpgsql to use this infrastructure for expressions that it's
already deemed "simple" (which in particular will never contain table
references).

The fast path still requires checking that search_path hasn't changed,
so provide a fast path for OverrideSearchPathMatchesCurrent by
counting changes that have occurred to the active search path in the
current session.  This is simplistic but seems enough for now, seeing
that PushOverrideSearchPath is not used in any performance-critical
cases.

Second, manage the refcounts on simple expressions' cached plans using
a transaction-lifespan resource owner, so that we only need to take
and release an expression's refcount once per transaction not once per
expression evaluation.  The management of this resource owner exactly
parallels the existing management of plpgsql's simple-expression EState.

Add some regression tests covering this area, in particular verifying
that expression caching doesn't break semantics for search_path changes.

Patch by me, but it owes something to previous work by Amit Langote,
who recognized that getting rid of plancache-related overhead would
be a useful thing to do here.  Also thanks to Andres Freund for review.

Discussion: https://postgr.es/m/CAFj8pRDRVfLdAxsWeVLzCAbkLFZhW549K+67tpOc-faC8uH8zw@mail.gmail.com

plpgsql_xact_cb ought to treat events XACT_EVENT_PARALLEL_COMMIT and
XACT_EVENT_PARALLEL_ABORT like XACT_EVENT_COMMIT and XACT_EVENT_ABORT
respectively, since its goal is to do process-local cleanup.  This
oversight caused plpgsql's end-of-transaction cleanup to not get done
in parallel workers.  Since a parallel worker will exit just after the
transaction cleanup, the effects of this are limited.  I couldn't find
any case in the core code with user-visible effects, but perhaps there
are some in extensions.  In any case it's wrong, so let's fix it before
it bites us not after.

In passing, add some comments around the handling of expression
evaluation resources in DO blocks.  There's no live bug there, but it's
quite unobvious what's happening; at least I thought so.  This isn't
related to the other issue, except that I found both things while poking
at expression-evaluation performance.

Back-patch the plpgsql_xact_cb fix to 9.5 where those event types
were introduced, and the DO-block commentary to v11 where DO blocks
gained the ability to issue COMMIT/ROLLBACK.

Discussion: https://postgr.es/m/10353.1585247879@sss.pgh.pa.us

Author: Daniel Gustafsson <daniel@yesql.se>

When SaveSlotToPath() is called with elevel=LOG, the early exits didn't
release the slot's io_in_progress_lock.

This could result in a walsender being stuck on the lock forever.  A
possible way to get into this situation is if the offending code paths
are triggered in a low disk space situation.

Author: Pavan Deolasee <pavan.deolasee@2ndquadrant.com>
Reported-by: Craig Ringer <craig@2ndquadrant.com>
Discussion: https://www.postgresql.org/message-id/flat/56a138c5-de61-f553-7e8f-6789296de785%402ndquadrant.com

The Makefile should set TAP_TESTS = 1, not implement the infrastructure
for itself.  For one thing, it missed the appropriate "make clean"
steps.  For another, the buildfarm isn't running this test because
it wasn't hooked into "make installcheck" either.

Commit 896fcdb2 contained an unnecessary setting that listened to
localhost. Since the test doesn't actually try to make an SSL connection
to the database this isn't required. Moreover, it's a security hole.

Per gripe from Tom Lane.

Some platforms require libssl to be linked explicitly in the new
SSL test module.  Borrow contrib/sslinfo's code for that.

Since src/test/modules/Makefile now has a variable SUBDIRS list,
it needs to follow the ALWAYS_SUBDIRS protocol for that (cf.
comments in Makefile.global.in).

Blindly try to fix MSVC build failures by adding PGDLLIMPORT.

The default hook function sets the default password callback function.
In order to allow preloaded libraries to have an opportunity to override
the default, TLS initialization if now delayed slightly until after
shared preloaded libraries have been loaded.

A test module is provided which contains a trivial example that decodes
an obfuscated password for an SSL certificate.

Author: Andrew Dunstan
Reviewed By: Andreas Karlsson, Asaba Takanori
Discussion: https://postgr.es/m/04116472-818b-5859-1d74-3d995aab2252@2ndQuadrant.com

Some getopt_long implementations don't like to have a non-option
argument before option arguments, so put the database name as the
last switch.

Per buildfarm member hoverfly.

The new command-line switch --include-foreign-data=PATTERN lets the user
specify foreign servers from which to dump foreign table data.  This can
be refined by further inclusion/exclusion switches, so that the user has
full control over which tables to dump.

A limitation is that this doesn't work in combination with parallel
dumps, for implementation reasons.  This might be lifted in the future,
but requires shuffling some code around.

Author: Luis Carril <luis.carril@swarm64.com>
Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
Reviewed-by: Surafel Temesgen <surafel3000@gmail.com>
Reviewed-by: vignesh C <vignesh21@gmail.com>
Reviewed-by: Álvaro Herrera <alvherre@2ndQuadrant.com>
Discussion: https://postgr.es/m/LEJPR01MB0185483C0079D2F651B16231E7FC0@LEJPR01MB0185.DEUPRD01.PROD.OUTLOOK.DE

This reverts the parts of commit 17a28b03
that changed ereport's auxiliary functions from returning dummy integer
values to returning void.  It turns out that a minority of compilers
complain (not entirely unreasonably) about constructs such as

	(condition) ? errdetail(...) : 0

if errdetail() returns void rather than int.  We could update those
call sites to say "(void) 0" perhaps, but the expectation for this
patch set was that ereport callers would not have to change anything.
And this aspect of the patch set was already the most invasive and
least compelling part of it, so let's just drop it.

Per buildfarm.

Discussion: https://postgr.es/m/CA+fd4k6N8EjNvZpM8nme+y+05mz-SM8Z_BgkixzkA34R+ej0Kw@mail.gmail.com

It was for unclear reasons defined in a separate location, which makes
it more cumbersome to override for testing, and it also did not have
any prominent documentation.  Move to pg_config_manual.h, where
similar things are already collected.

The previous definition on the command-line had the effect of defining
it to the value 1, but now that we don't need that anymore we just
define it to empty, to simplify manual editing a bit.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/b7053ba8-b008-5335-31de-2fe4fe41ef0f%402ndquadrant.com

The name of E182 was changed in SQL:2011.

Also, we can change it to supported because all it requires is one
embedded language to be supported, which we do.

On Vista and later, use GetNLSVersionEx() to request collation version
information.
Reviewed-by: Juan José Santamaría Flecha <juanjo.santamaria@gmail.com>
Discussion: https://postgr.es/m/CA%2BhUKGJvqup3s%2BJowVTcacZADO6dOhfdBmvOPHLS3KXUJu41Jw%40mail.gmail.com

Remove the documented restriction that collation providers must either
return NULL for all collations or non-NULL for all collations.

Use NULL for glibc collations like "C.UTF-8", which might otherwise lead
future proposed commits to force unnecessary index rebuilds.
Reviewed-by: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Discussion: https://postgr.es/m/CA%2BhUKGJvqup3s%2BJowVTcacZADO6dOhfdBmvOPHLS3KXUJu41Jw%40mail.gmail.com

Correct oversight in 1f39bce0. If enable_hashagg_disk=true, we should
consider hash aggregation for DISTINCT when applicable.

If there are no aggregates, there is no need to allocate an array of
zero AggStatePerGroupData elements.

Descriptions of some aspects of how deduplication works were unclear in
a couple of places.

Measurements show, and intuition agrees, that there's currently no
known cases where adding a fastpath to avoid allocating / ordering a
heap for a single transaction is worthwhile.

Author: Dilip Kumar
Discussion: https://postgr.es/m/CAFiTN-sp701wvzvnLQJGk7JDqrFM8f--97-ihbwkU8qvn=p8nw@mail.gmail.com

bf68b79e introduced an unused variable
compiler warning on Cygwin.

Change all the auxiliary error-reporting routines to return void,
now that we no longer need to pretend they are passing something
useful to errfinish().  While this probably doesn't save anything
significant at the machine-code level, it allows detection of some
additional types of mistakes.

Pass the error location details (__FILE__, __LINE__, PG_FUNCNAME_MACRO)
to errfinish not errstart.  This shaves a few cycles off the case where
errstart decides we're not going to emit anything.

Re-implement elog() as a trivial wrapper around ereport(), removing
the separate support infrastructure it used to have.  Aside from
getting rid of some now-surplus code, this means that elog() now
really does have exactly the same semantics as ereport(), in particular
that it can skip evaluation work if the message is not to be emitted.

Andres Freund and Tom Lane

Discussion: https://postgr.es/m/CA+fd4k6N8EjNvZpM8nme+y+05mz-SM8Z_BgkixzkA34R+ej0Kw@mail.gmail.com

Now that we require C99, we can depend on __VA_ARGS__ to work, and
revising ereport() to use it has several significant benefits:

* The extra parentheses around the auxiliary function calls are now
optional.  Aside from being a bit less ugly, this removes a common
gotcha for new contributors, because in some cases the compiler errors
you got from forgetting them were unintelligible.

* The auxiliary function calls are now evaluated as a comma expression
list rather than as extra arguments to errfinish().  This means that
compilers can be expected to warn about no-op expressions in the list,
allowing detection of several other common mistakes such as forgetting
to add errmsg(...) when converting an elog() call to ereport().

* Unlike the situation with extra function arguments, comma expressions
are guaranteed to be evaluated left-to-right, so this removes platform
dependency in the order of the auxiliary function calls.  While that
dependency hasn't caused us big problems in the past, this change does
allow dropping some rather shaky assumptions around errcontext() domain
handling.

There's no intention to make wholesale changes of existing ereport
calls, but as proof-of-concept this patch removes the extra parens
from a couple of calls in postgres.c.

While new code can be written either way, code intended to be
back-patched will need to use extra parens for awhile yet.  It seems
worth back-patching this change into v12, so as to reduce the window
where we have to be careful about that by one year.  Hence, this patch
is careful to preserve ABI compatibility; a followup HEAD-only patch
will make some additional simplifications.

Andres Freund and Tom Lane

Discussion: https://postgr.es/m/CA+fd4k6N8EjNvZpM8nme+y+05mz-SM8Z_BgkixzkA34R+ej0Kw@mail.gmail.com

A variable was unused in non-assert builds.  Simplify the code to
avoid the issue.
Reported-by: Erik Rijkers <er@xs4all.nl>

Sloppiness in commit cedffbdb, noted by Erikjan Rijkers.
(It's fairly unfortunate that xmllint doesn't catch this.)

Discussion: https://postgr.es/m/2e3dc9e4bfa4802d2c9f5fe15bde44de@xs4all.nl

This moves the main operations of apply_handle_{insert|update|delete},
that of inserting, updating, deleting a tuple into/from a given
relation, into corresponding
apply_handle_{insert|update|delete}_internal functions.  This allows
performing those operations on relations that are not directly the
targets of replication, which is something a later patch will use for
targeting partitioned tables.

Author: Amit Langote <amitlangote09@gmail.com>
Reviewed-by: Rafia Sabih <rafia.pghackers@gmail.com>
Reviewed-by: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Discussion: https://www.postgresql.org/message-id/flat/CA+HiwqH=Y85vRK3mOdjEkqFK+E=ST=eQiHdpj43L=_eJMOOznQ@mail.gmail.com

It previously only supported NFKC, for use by SASLprep.  This expands
the API to offer the choice of all four normalization forms.  Right
now, there are no internal users of the forms other than NFKC.
Reviewed-by: Daniel Verite <daniel@manitou-mail.org>
Reviewed-by: Andreas Karlsson <andreas@proxel.se>
Discussion: https://www.postgresql.org/message-id/flat/c1909f27-c269-2ed9-12f8-3ab72c8caf7a@2ndquadrant.com

Author: Justin Pryzby
Discussion: https://postgr.es/m/20200321040750.GD13662@telsasoft.com

Previously if a promotion was triggered while recovery was paused,
the paused state continued. Also recovery could be paused by executing
pg_wal_replay_pause() even while a promotion was ongoing. That is,
recovery pause had higher priority over a standby promotion.
But this behavior was not desirable because most users basically wanted
the recovery to complete as soon as possible and the server to become
the master when they requested a promotion.

This commit changes recovery so that it prefers a promotion over
recovery pause. That is, if a promotion is triggered while recovery
is paused, the paused state ends and a promotion continues. Also
this commit makes recovery pause functions like pg_wal_replay_pause()
throw an error if they are executed while a promotion is ongoing.

Internally, this commit adds new internal function PromoteIsTriggered()
that returns true if a promotion is triggered. Since the name of
this function and the existing function IsPromoteTriggered() are
confusingly similar, the commit changes the name of IsPromoteTriggered()
to IsPromoteSignaled, as more appropriate name.

Author: Fujii Masao
Reviewed-by: Atsushi Torikoshi, Sergei Kornilov
Discussion: https://postgr.es/m/00c194b2-dbbb-2e8a-5b39-13f14048ef0a@oss.nttdata.com

restore_command has only been used until now by the backend, but there
is a pending patch for pg_rewind to make use of that in the frontend.

Author: Alexey Kondratov
Reviewed-by: Andrey Borodin, Andres Freund, Alvaro Herrera, Alexander
Korotkov, Michael Paquier
Discussion: https://postgr.es/m/a3acff50-5a0d-9a2c-b3b2-ee36168955c1@postgrespro.ru

This commit introduces new wait events BackupWaitWalArchive and
RecoveryPause. The former is reported while waiting for the WAL files
required for the backup to be successfully archived. The latter is
reported while waiting for recovery in pause state to be resumed.

Author: Fujii Masao
Reviewed-by: Michael Paquier, Atsushi Torikoshi, Robert Haas
Discussion: https://postgr.es/m/f0651f8c-9c96-9f29-0ff9-80414a15308a@oss.nttdata.com

Discussion: https://postgr.es/m/23196.1584943506@sss.pgh.pa.us