Backpatch-through: certain files through 9.3

Multiple sessions doing CREATE INDEX CONCURRENTLY simultaneously are
supposed to be able to work in parallel, as evidenced by fixes in commit
c3d09b3b specifically to support this case.  In reality, one of the
sessions would be aborted by a misterious "deadlock detected" error.

Jeff Janes diagnosed that this is because of leftover snapshots used for
system catalog scans -- this was broken by 8aa3e475 keeping track of
(registering) the catalog snapshot.  To fix the deadlocks, it's enough
to de-register that snapshot prior to waiting.

Backpatch to 9.4, which introduced MVCC catalog scans.

Include an isolationtester spec that 8 out of 10 times reproduces the
deadlock with the unpatched code for me (Álvaro).

Author: Jeff Janes
Diagnosed-by: Jeff Janes
Reported-by: Jeremy Finzel
Discussion: https://postgr.es/m/CAMa1XUhHjCv8Qkx0WOr1Mpm_R4qxN26EibwCrj0Oor2YBUFUTg%40mail.gmail.com

Otherwise, the test fails with "Timed out while waiting for standby to
catch up".  This happened rarely, perhaps only when autovacuum wrote WAL
between our choosing the recovery target and choosing the LSN to await.
Commit b26f7fa6 fixed one case of this.
Fix two more.  Back-patch to 9.6, which introduced the affected test.

Discussion: https://postgr.es/m/20180101055227.GA2952815@rfd.leadboat.com

When walsenders were included in pg_stat_activity, only the ones
actually streaming WAL were listed as active when they were active. In
particular, the connections sending base backups were listed as being
idle. Which means that a regular pg_basebackup would show up with one
active and one idle connection, when both were active.

This patch updates to set all walsenders to active when they are
(including those doing very fast things like IDENTIFY_SYSTEM), and then
back to idle. Details about exactly what they are doing is available in
pg_stat_replication.

Patch by me, review by Michael Paquier and David Steele.

Hash index depends on estimation of numbers of tuples and pages of relations,
incorrect value could be a reason of significantly growing of index. Vacuum
full recreates heap and reindex all indexes before renewal stats. The patch
fixes that, so indexes will see correct values.

Backpatch to v10 only because earlier versions haven't usable hash index and
growing of hash index is a single user-visible symptom.

Author: Amit Kapila
Reviewed-by: Ashutosh Sharma, me
Discussion: https://www.postgresql.org/message-id/flat/20171115232922.5tomkxnw3iq6jsg7@inml.weebeastie.net

Since 9.4, we've allowed the syntax "select union select" and variants
of that.  However, the planner wasn't expecting a no-column set operation
and ended up treating the set operation as if it were UNION ALL.

Turns out it's trivial to fix in v10 and later; we just need to be careful
about not generating a Sort node with no sort keys.  However, since a weird
corner case like this is never going to be exercised by developers, we'd
better have thorough regression tests if we want to consider it supported.

Per report from Victor Yegorov.

Discussion: https://postgr.es/m/CAGnEbojGJrRSOgJwNGM7JSJZpVAf8xXcVPbVrGdhbVEHZ-BUMw@mail.gmail.com

Generally, error recovery paths that need to do things like
LWLockReleaseAll and pgstat_report_wait_end also need to call
ConditionVariableCancelSleep, but AbortSubTransaction was missed.

Since subtransaction abort might destroy up the DSM segment that
contains the ConditionVariable stored in cv_sleep_target, this
can result in a crash for anything using condition variables.

Reported and diagnosed by Andres Freund.

Discussion: http://postgr.es/m/20171221110048.rxk6464azzl5t2fi@alap3.anarazel.de

Otherwise, when the query string is read, we might trailing garbage
beyond the end, unless there happens to be a \0 there by good luck.

Report and patch by Thomas Munro. Reviewed by Rafia Sabih.

Discussion: http://postgr.es/m/CAEepm=2SJs7X+_vx8QoDu8d1SMEOxtLhxxLNzZun_BvNkuNhrw@mail.gmail.com

When a Gather or Gather Merge node is started and stopped multiple
times, accumulate instrumentation data only once, at the end, instead
of after each execution, to avoid recording inflated totals.

Commit 778e78ae, the previous attempt
at a fix, instead reset the state after every execution, which worked
for the general instrumentation data but had problems for the additional
instrumentation specific to Sort and Hash nodes.

Report by hubert depesz lubaczewski.  Analysis and fix by Amit Kapila,
following a design proposal from Thomas Munro, with a comment tweak
by me.

Discussion: http://postgr.es/m/20171127175631.GA405@depesz.com

oversight in 244c8b46

Reported-by: Blaz Merela <blaz@merela.org>

Previously an assertion failure occurred when pg_stop_backup() for
non-exclusive backup was aborted while it's waiting for WAL files to
be archived. This assertion failure happened in do_pg_abort_backup()
which was called when a non-exclusive backup was canceled.
do_pg_abort_backup() assumes that there is at least one non-exclusive
backup running when it's called. But pg_stop_backup() can be canceled
even after it marks the end of non-exclusive backup (e.g.,
during waiting for WAL archiving). This broke the assumption that
do_pg_abort_backup() relies on, and which caused an assertion failure.

This commit changes do_pg_abort_backup() so that it does nothing
when non-exclusive backup has been already marked as completed.
That is, the asssumption is also changed, and do_pg_abort_backup()
now can handle even the case where it's called when there is
no running backup.

Backpatch to 9.6 where SQL-callable non-exclusive backup was added.

Author: Masahiko Sawada and Michael Paquier
Reviewed-By: Robert Haas and Fujii Masao
Discussion: https://www.postgresql.org/message-id/CAD21AoD2L1Fu2c==gnVASMyFAAaq3y-AQ2uEVj-zTCGFFjvmDg@mail.gmail.com

es_query_dsa turns out to be broken by design, because it supposes
that there is only one DSA for the whole query, whereas there is
actually one per Gather (Merge) node.  For now, work around that
problem by setting and clearing the pointer around the sections of
code that might need it.  It's probably a better idea to get rid of
es_query_dsa altogether in favor of having each node keep track
individually of which DSA is relevant, but that seems like more than
we would want to back-patch.

Thomas Munro, reviewed and tested by Andreas Seltenreich, Amit
Kapila, and by me.

Discussion: http://postgr.es/m/CAEepm=1U6as=brnVvMNixEV2tpi8NuyQoTmO8Qef0-VV+=7MDA@mail.gmail.com

Don't write to stdin of a psql process that could have already exited
with an authentication failure.  Buildfarm members crake and mandrill
have failed once by doing so.  Ignore SIGPIPE in all TAP tests.
Back-patch to v10, where these tests were introduced.

Reviewed by Michael Paquier.

Discussion: https://postgr.es/m/20171209210203.GC3362632@rfd.leadboat.com

The previous commit has shown that the sanity checks around freezing
aren't strong enough. Strengthening them seems especially important
because the existance of the bug has caused corruption that we don't
want to make even worse during future vacuum cycles.

The errors are emitted with ereport rather than elog, despite being
"should never happen" messages, so a proper error code is emitted. To
avoid superflous translations, mark messages as internal.

Author: Andres Freund and Alvaro Herrera
Reviewed-By: Alvaro Herrera, Michael Paquier
Discussion: https://postgr.es/m/20171102112019.33wb7g5wp4zpjelu@alap3.anarazel.de
Backpatch: 9.3-

Previously it was possible that a tuple was not pruned during vacuum,
even though its update xmax (i.e. the updating xid in a multixact with
both key share lockers and an updater) was below the cutoff horizon.

As the freezing code assumed, rightly so, that that's not supposed to
happen, xmax would be preserved (as a member of a new multixact or
xmax directly). That causes two problems: For one the tuple is below
the xmin horizon, which can cause problems if the clog is truncated or
once there's an xid wraparound. The bigger problem is that that will
break HOT chains, which in turn can lead two to breakages: First,
failing index lookups, which in turn can e.g lead to constraints being
violated. Second, future hot prunes / vacuums can end up making
invisible tuples visible again. There's other harmful scenarios.

Fix the problem by recognizing that tuples can be DEAD instead of
RECENTLY_DEAD, even if the multixactid has alive members, if the
update_xid is below the xmin horizon. That's safe because newer
versions of the tuple will contain the locking xids.

A followup commit will harden the code somewhat against future similar
bugs and already corrupted data.

Author: Andres Freund, with changes by Alvaro Herrera
Reported-By: Daniel Wood
Analyzed-By: Andres Freund, Alvaro Herrera, Robert Haas, Peter
   Geoghegan, Daniel Wood, Yi Wen Wong, Michael Paquier
Reviewed-By: Alvaro Herrera, Robert Haas, Michael Paquier
Discussion:
    https://postgr.es/m/E5711E62-8FDF-4DCA-A888-C200BF6B5742@amazon.com
    https://postgr.es/m/20171102112019.33wb7g5wp4zpjelu@alap3.anarazel.de
Backpatch: 9.3-

The logical slots have a fast code path for sending data so as not to
impose too high a per message overhead. The fast path skips checks for
interrupts and timeouts. However, the existing coding failed to consider
the fact that a transaction with a large number of changes may take a
very long time to be processed and sent to the client. This causes the
walsender to ignore interrupts for potentially a long time and more
importantly it will result in the walsender being killed due to
timeout at the end of such a transaction.

This commit changes the fast path to also check for interrupts and only
allows calling the fast path when the last keepalive check happened less
than half the walsender timeout ago. Otherwise the slower code path will
be taken.

Backpatched to 9.4

Petr Jelinek, reviewed by  Kyotaro HORIGUCHI, Yura Sokolov,  Craig
Ringer and Robert Haas.

Discussion: https://postgr.es/m/e082a56a-fd95-a250-3bae-0fff93832510@2ndquadrant.com

The previous coding forgot to release the scan before seizing
it again, leading to a lockup.

Report by Patrick Hemmer.  Diagnosis by Thomas Munro.  Patch by
Amit Kapila.

Discussion: http://postgr.es/m/CAEepm=2xZUcOGP9V0O_G0=2P2wwXwPrkF=upWTCJSisUxMnuSg@mail.gmail.com

This reverts commit 778e78ae.  Per
further discussion, that doesn't seem to be the best possible fix.

Discussion: http://postgr.es/m/CAA4eK1LW2aFKzY3=vwvc=t-juzPPVWP2uT1bpx_MeyEqnM+p8g@mail.gmail.com

Reported-by: Noah Misch <noah@leadboat.com>

I noticed that _SPI_execute_plan initially sets spierrcontext.arg = NULL,
and only fills it in some time later.  If an error were to happen in
between, _SPI_error_callback would try to dereference the null pointer.
This is unlikely --- there's not much between those points except
push-snapshot calls --- but it's clearly not impossible.  Tweak the
callback to do nothing if the pointer isn't set yet.

It's been like this for awhile, so back-patch to all supported branches.

Reported by Robins Tharakan

Notably, this permits linking to the 32-bit Perl binaries advertised on
perl.org, namely Strawberry Perl and ActivePerl.  This has a side effect
of permitting linking to binaries built with obsolete MSVC versions.

By default, MSVC 2012 and later require a "safe exception handler table"
in each binary.  MinGW-built, 32-bit DLLs lack the relevant exception
handler metadata, so linking to them failed with error LNK2026.  Restore
the semantics of MSVC 2010, which omits the table from a given binary if
some linker input lacks metadata.  This has no effect on 64-bit builds
or on MSVC 2010 and earlier.  Back-patch to 9.3 (all supported
versions).

Reported by Victor Wagner.

Discussion: https://postgr.es/m/20160326154321.7754ab8f@wagner.wagner.home

Commits 5a5c2fec and
b5178c5d introduced support for modern
MSVC-built, 32-bit Perl, but they broke use of MinGW-built, 32-bit Perl
distributions like Strawberry Perl and modern ActivePerl.  Perl has no
robust means to report whether it expects a -D_USE_32BIT_TIME_T ABI, so
test this.  Back-patch to 9.3 (all supported versions).

The chief alternative was a heuristic of adding -D_USE_32BIT_TIME_T when
$Config{gccversion} is nonempty.  That banks on every gcc-built Perl
using the same ABI.  gcc could change its default ABI the way MSVC once
did, and one could build Perl with gcc and the non-default ABI.

The GNU make build system could benefit from a similar test, without
which it does not support MSVC-built Perl.  For now, just add a comment.
Most users taking the special step of building Perl with MSVC probably
build PostgreSQL with MSVC.

Discussion: https://postgr.es/m/20171130041441.GA3161526@rfd.leadboat.com

Those cases currently crash and supporting them is more work then
originally thought, so we'll just prohibit these scenarios for now.

Author: Michael Paquier <michael.paquier@gmail.com>
Reviewed-by: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>
Reported-by: Мансур Галиев <gomer94@yandex.ru>
Bug: #14866

Reported-by: Masahiko Sawada <sawada.mshk@gmail.com>

Add support to the SCRAM exchange for clients that support channel
binding, such as PostgreSQL version 11 and beyond.  If such a client
encounters a PostgreSQL 10 server that does not support channel binding,
it will send a channel binding flag 'y', meaning the client supports
channel binding but thinks the server does not.  But PostgreSQL 10
erroneously did not accept that flag.  This would cause connections to
fail if a version 11 client connects to a version 10 server with SCRAM
authentication over SSL.

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

A COPY into a table should apply identity sequence values just like it
does for ordinary defaults.  This was previously forgotten, leading to
null values being inserted, which in turn would fail because identity
columns have not-null constraints.

Author: Michael Paquier <michael.paquier@gmail.com>
Reported-by: Steven Winfield <steven.winfield@cantabcapital.com>
Bug: #14952

When a worker is flagged as BGW_NEVER_RESTART and we fail to start it,
or if it is not marked BGW_NEVER_RESTART but is terminated before
startup succeeds, what BgwHandleStatus should be reported?  The
previous code really hadn't considered this possibility (as indicated
by the comments which ignore it completely) and would typically return
BGWH_NOT_YET_STARTED, but that's not a good answer, because then
there's no way for code using GetBackgroundWorkerPid() to tell the
difference between a worker that has not started but will start
later and a worker that has not started and will never be started.
So, when this case happens, return BGWH_STOPPED instead.  Update the
comments to reflect this.

The preceding fix by itself is insufficient to fix the problem,
because the old code also didn't send a notification to the process
identified in bgw_notify_pid when startup failed.  That might've
been technically correct under the theory that the status of the
worker was BGWH_NOT_YET_STARTED, because the status would indeed not
change when the worker failed to start, but now that we're more
usefully reporting BGWH_STOPPED, a notification is needed.

Without these fixes, code which starts background workers and then
uses the recommended APIs to wait for those background workers to
start would hang indefinitely if the postmaster failed to fork a
worker.

Amit Kapila and Robert Haas

Discussion: http://postgr.es/m/CAA4eK1KDfKkvrjxsKJi3WPyceVi3dH1VCkbTJji2fuwKuB=3uw@mail.gmail.com

Reported-by: Dave Page <dpage@pgadmin.org>

When a Gather or Gather Merge node is started and stopped multiple
times, the old code wouldn't reset the shared state between executions,
potentially resulting in dramatically inflated instrumentation data
for nodes beneath it.  (The per-worker instrumentation ended up OK,
I think, but the overall totals were inflated.)

Report by hubert depesz lubaczewski.  Analysis and fix by Amit Kapila,
reviewed and tweaked a bit by me.

Discussion: http://postgr.es/m/20171127175631.GA405@depesz.com

This makes life easier for extension authors who wish to support
Windows.

Brian Cloutier, slightly amended by me.

Discussion: http://postgr.es/m/CAJCy68fscdNhmzFPS4kyO00CADkvXvEa-28H-OtENk-pa2OTWw@mail.gmail.com

This ensures that automatically generated HTML anchors don't change in
every build.

This patch fixes a couple of low-probability bugs that could lead to
reporting an irrelevant errno value (and hence possibly a wrong SQLSTATE)
concerning directory-open or file-open failures.  It also fixes places
where we took shortcuts in reporting such errors, either by using elog
instead of ereport or by using ereport but forgetting to specify an
errcode.  And it eliminates a lot of just plain redundant error-handling
code.

In service of all this, export fd.c's formerly-static function
ReadDirExtended, so that external callers can make use of the coding
pattern

	dir = AllocateDir(path);
	while ((de = ReadDirExtended(dir, path, LOG)) != NULL)

if they'd like to treat directory-open failures as mere LOG conditions
rather than errors.  Also fix FreeDir to be a no-op if we reach it
with dir == NULL, as such a coding pattern would cause.

Then, remove code at many call sites that was throwing an error or log
message for AllocateDir failure, as ReadDir or ReadDirExtended can handle
that job just fine.  Aside from being a net code savings, this gets rid of
a lot of not-quite-up-to-snuff reports, as mentioned above.  (In some
places these changes result in replacing a custom error message such as
"could not open tablespace directory" with more generic wording "could not
open directory", but it was agreed that the custom wording buys little as
long as we report the directory name.)  In some other call sites where we
can't just remove code, change the error reports to be fully
project-style-compliant.

Also reorder code in restoreTwoPhaseData that was acquiring a lock
between AllocateDir and ReadDir; in the unlikely but surely not
impossible case that LWLockAcquire changes errno, AllocateDir failures
would be misreported.  There is no great value in opening the directory
before acquiring TwoPhaseStateLock, so just do it in the other order.

Also fix CheckXLogRemoved to guarantee that it preserves errno,
as quite a number of call sites are implicitly assuming.  (Again,
it's unlikely but I think not impossible that errno could change
during a SpinLockAcquire.  If so, this function was broken for its
own purposes as well as breaking callers.)

And change a few places that were using not-per-project-style messages,
such as "could not read directory" when "could not open directory" is
more correct.

Back-patch the exporting of ReadDirExtended, in case we have occasion
to back-patch some fix that makes use of it; it's not needed right now
but surely making it global is pretty harmless.  Also back-patch the
restoreTwoPhaseData and CheckXLogRemoved fixes.  The rest of this is
essentially cosmetic and need not get back-patched.

Michael Paquier, with a bit of additional work by me

Discussion: https://postgr.es/m/CAB7nPqRpOCxjiirHmebEFhXVTK7V5Jvw4bz82p7Oimtsm3TyZA@mail.gmail.com

There's no good reason that the multicolumn stats stuff shouldn't work on
booleans.  But it looked only for "Var = pseudoconstant" clauses, and it
will seldom find those for boolean Vars, since earlier phases of planning
will fold "boolvar = true" or "boolvar = false" to just "boolvar" or
"NOT boolvar" respectively.  Improve dependencies_clauselist_selectivity()
to recognize such clauses as equivalent to equality restrictions.

This fixes a failure of the extended stats mechanism to apply in a case
reported by Vitaliy Garnashevich.  It's not a complete solution to his
problem because the bitmap-scan costing code isn't consulting extended
stats where it should, but that's surely an independent issue.

In passing, improve some comments, get rid of a NumRelids() test that's
redundant with the preceding bms_membership() test, and fix
dependencies_clauselist_selectivity() so that estimatedclauses actually
is a pure output argument as stated by its API contract.

Back-patch to v10 where this code was introduced.

Discussion: https://postgr.es/m/73a4936d-2814-dc08-ed0c-978f76f435b0@gmail.com

Invoking the Makefile without an explicit target was building every
possible target instead of just the "all" target.  Back-patch to 9.3
(all supported versions).

This is simpler and more closely follows overwhelming precedent.

Report and patch by Mark Dilger.
Discussion: https://postgr.es/m/9A68FB88-5F45-4848-9926-8586E2D777D1@gmail.com

This is a mistakenly placed conditional in bf2a691e.

Reported by Justin Pryzby
Discussion: https://postgr.es/m/20171117214352.GE25796@telsasoft.com

Commit d4663350 changed things so
that shm_toc_lookup would fail with an error rather than silently
returning NULL in the hope that such failures would be reported
in a useful way rather than via a system crash.  However, it
overlooked the fact that the lookup of PARALLEL_KEY_ERROR_QUEUE
in ReinitializeParallelDSM is expected to fail when no DSM segment
was created in the first place; in that case, we end up with a
backend-private memory segment that still contains an entry for
PARALLEL_KEY_FIXED but no others.  Consequently a benign failure
to initialize parallelism can escalate into an elog(ERROR);
repair.

Discussion: http://postgr.es/m/CA+Tgmob8LFw55DzH1QEREpBEA9RJ_W_amhBFCVZ6WMwUhVpOqg@mail.gmail.com

If we have a plan that uses parallelism but are unable to execute it
using parallelism, for example due to a lack of available DSM
segments, then the EState's es_query_dsa will be NULL.  Parallel
bitmap heap scan needs to fall back to a non-parallel scan in such
cases.

Patch by me, reviewed by Dilip Kumar

Discussion: http://postgr.es/m/CAEepm=0kADK5inNf_KuemjX=HQ=PuTP0DykM--fO5jS5ePVFEA@mail.gmail.com

Allows triggers to operate correctly

Author: Petr Jelinek <petr.jelinek@2ndquadrant.com>
Reported-by: Konstantin Knizhnik <k.knizhnik@postgrespro.ru>