Several places in fd.c had badly-thought-through handling of error returns
from lseek() and close().  The fact that those would seldom fail on valid
FDs is probably the reason we've not noticed this up to now; but if they
did fail, we'd get quite confused.

LruDelete and LruInsert actually just Assert'd that lseek never fails,
which is pretty awful on its face.

In LruDelete, we indeed can't throw an error, because that's likely to get
called during error abort and so throwing an error would probably just lead
to an infinite loop.  But by the same token, throwing an error from the
close() right after that was ill-advised, not to mention that it would've
left the LRU state corrupted since we'd already unlinked the VFD from the
list.  I also noticed that really, most of the time, we should know the
current seek position and it shouldn't be necessary to do an lseek here at
all.  As patched, if we don't have a seek position and an lseek attempt
doesn't give us one, we'll close the file but then subsequent re-open
attempts will fail (except in the somewhat-unlikely case that a
FileSeek(SEEK_SET) call comes between and allows us to re-establish a known
target seek position).  This isn't great but it won't result in any state
corruption.

Meanwhile, having an Assert instead of an honest test in LruInsert is
really dangerous: if that lseek failed, a subsequent read or write would
read or write from the start of the file, not where the caller expected,
leading to data corruption.

In both LruDelete and FileClose, if close() fails, just LOG that and mark
the VFD closed anyway.  Possibly leaking an FD is preferable to getting
into an infinite loop or corrupting the VFD list.  Besides, as far as I can
tell from the POSIX spec, it's unspecified whether or not the file has been
closed, so treating it as still open could be the wrong thing anyhow.

I also fixed a number of other places that were being sloppy about
behaving correctly when the seekPos is unknown.

Also, I changed FileSeek to return -1 with EINVAL for the cases where it
detects a bad offset, rather than throwing a hard elog(ERROR).  It seemed
pretty inconsistent that some bad-offset cases would get a failure return
while others got elog(ERROR).  It was missing an offset validity check for
the SEEK_CUR case on a closed file, too.

Back-patch to all supported branches, since all this code is fundamentally
identical in all of them.

Discussion: https://postgr.es/m/2982.1487617365@sss.pgh.pa.us

There's some ongoing performance work on this area, so let's make sure
we don't break things.

Extracted from a larger patch originally by Stas Kelvich.

Authors: Stas Kelvich, Nikhil Sontakke, Michael Paquier
Discussion: https://postgr.es/m/CAMGcDxfsuLLOg=h5cTg3g77Jjk-UGnt=RW7zK57zBSoFsapiWA@mail.gmail.com

neha khatri

Previously the command forgot to close the connection to the publisher
when it failed to drop the replication slot.

Walsender uses the local buffers for each outgoing and incoming message.
Previously when creating replication slot, walsender forgot to initialize
one of them and which can cause the segmentation fault error. To fix this
issue, this commit changes walsender so that it always initialize them
before it executes the requested replication command.

Back-patch to 9.4 where replication slot was introduced.

Problem report and initial patch by Stas Kelvich, modified by me.
Report: https://www.postgresql.org/message-id/A1E9CB90-1FAC-4CAD-8DBA-9AA62A6E97C5@postgrespro.ru

The initial table synchronization feature has not been supported yet,
but there was the confusing header comment about it in logical/worker.c.

Creating global objects named "foo" isn't an especially wise thing,
but especially not in a test script that has already used that name
for something else, and most especially not in a script that runs
in parallel with other scripts that use that name :-(

Per buildfarm.

Commit 04aad401 added this check after the search for a Python shared
library, which seems to me to be a pretty unfriendly ordering.  The
search might fail for what are basically version-related reasons, and
in such a case it'd be better to say "your Python is too old" than
"could not find shared library for Python".

There is no specific reason for this right now, but keeping support for
old Python versions around indefinitely increases the maintenance
burden.  The oldest supported Python version is now Python 2.4, which is
still shipped in RHEL/CentOS 5 by default.

In configure, add a check for the required Python version and give a
friendly error message for an old version, instead of relying on an
obscure build error later on.

Replace incorrect word "index" with "heap"

Takayuki Tsunakawa

Be specific about which pattern is being complained of, and avoid saying
"it's not supported in to_date", which is just confusing if the error is
actually coming out of to_timestamp.  We can phrase it as "is only
supported in to_char", instead.  Also, use the term "formatting field" not
"format pattern", because other error messages in the same file prefer that
terminology.  (This isn't terribly consistent with the documentation, so
maybe we should change all these error messages?)

These are only supported in to_char, not in the other direction, but the
documentation failed to mention that.  Also, describe TZ/tz as printing the
time zone "abbreviation", not "name", because what they print is elsewhere
referred to that way.  Per bug #14558.

It failed to remove a .o file during "make clean", and it lacked
a .gitignore file entirely.

It didn't take long at all for me to become irritated that the original
choice of name for this script resulted in "warning" showing up in several
places in build logs, because I tend to grep for that.  Change the script
name to avoid that.

One case in the PL/Tcl tests is observed to fail on RHEL5 with a Turkish
time zone setting.  It's not clear if this is an old Tcl bug or something
odd about the zone data, but in any case that test is meant to see if the
Tcl [clock] command works at all, not what its corner-case behaviors are.
Therefore we have no need to test exactly which week a Sunday midnight is
considered to fall into.  Probe the following Tuesday instead.

Discussion: https://postgr.es/m/797.1487517822@sss.pgh.pa.us

Versions of flex before 2.5.36 might generate code that results in an
"unused variable" warning, when using %option reentrant.  Historically
we've worked around that by specifying -Wno-error, but that's an
unsatisfying solution.  The official "fix" for this was just to insert a
dummy reference to the variable, so write a small perl script that edits
the generated C code similarly.

The MSVC side of this is untested, but the buildfarm should soon reveal
if I broke that.

Discussion: https://postgr.es/m/25456.1487437842@sss.pgh.pa.us

Previously, if the parent was specified as WITH OIDS, each child
also had to be explicitly specified as WITH OIDS.

Amit Langote, per a report from Simon Riggs.  Some additional
work on the documentation changes by me.

Discussion: http://postgr.es/m/CANP8+jJBpWocfKrbJcaf3iBt9E3U=WPE_NC8YE6rye+YJ1sYnQ@mail.gmail.com

Commit 5262f7a4 added similar support
for parallel index scans; this extends that work to index-only scans.
As with parallel index scans, this requires support from the index AM,
so currently parallel index-only scans will only be possible for btree
indexes.

Rafia Sabih, reviewed and tested by Rahila Syed, Tushar Ahuja,
and Amit Kapila

Discussion: http://postgr.es/m/CAOGQiiPEAs4C=TBp0XShxBvnWXuzGL2u++Hm1=qnCpd6_Mf8Fw@mail.gmail.com

A new function dsa_allocate_extended now takes flags which indicate
that huge allocations should be permitted, that out-of-memory
conditions should not throw an error, and/or that the returned memory
should be zero-filled, just like MemoryContextAllocateExtended.

Commit 9acb8559, which added
dsa_allocate0, was broken because it failed to account for the
possibility that dsa_allocate() might return InvalidDsaPointer.
This fixes that problem along the way.

Thomas Munro, with some comment changes by me.

Discussion: http://postgr.es/m/CA+Tgmobt7CcF_uQP2UQwWmu4K9qCHehMJP9_9m1urwP8hbOeHQ@mail.gmail.com

The recovery.conf file that's generated is specifically for replication,
and not needed (or wanted) for regular backup restore, so indicate that
in the message.

The way the old query was written prevented some join optimizations
because the join conditions were hidden inside a CASE expression.  With
a large number of constraints, the query became unreasonably slow.  The
new query performs much better.

From: Alexey Bashtanov <bashtanov@imap.cc>
Reviewed-by: Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>

From: Thom Brown <thom@linux.com>

Also add to the existing rather half-baked description of PROFILE,
which does exactly the same thing, but I think people use it differently.

Discussion: https://postgr.es/m/16461.1487361849@sss.pgh.pa.us

This could lead to incorrect dumping of language privileges in some
cases, which is probably a rare situation.

This was probably forgotten to be removed when general recursion support
was added.

This does the same thing as dsa_allocate, except that the memory
is guaranteed to be zero-filled on return.

Dilip Kumar, adjusted by me.

This causes a warning with the old html-docs toolchain, though not with the
new.  I had originally supposed that we needed both <indexterm> entries to
get both a primary index entry and a see-also link; but evidently not,
as pointed out by Fabien Coelho.

Discussion: https://postgr.es/m/alpine.DEB.2.20.1702161616060.5445@lancre

Amit Langote, reviewed and slightly changed by me.

Make the typedefs for output plugins consistent with project style;
they were previously not even consistent with each other as to layout
or inclusion of parameter names.  Make the documentation look the same,
and fix errors therein (missing and misdescribed parameters).

Back-patch because of the documentation bugs.

There's no such field as OutputPluginOptions.output_mode;
it's actually output_type.  Noted by T. Katsumata.

Discussion: https://postgr.es/m/20170215072115.6101.29870@wrigleys.postgresql.org

The loops in ExecHashJoinNewBatch(), ExecHashIncreaseNumBatches(), and
ExecHashRemoveNextSkewBucket() are all capable of iterating over many
tuples without ever doing a CHECK_FOR_INTERRUPTS, so that the backend
might fail to respond to SIGINT or SIGTERM for an unreasonably long time.
Fix that.  In the case of ExecHashJoinNewBatch(), it seems useful to put
the added CHECK_FOR_INTERRUPTS into ExecHashJoinGetSavedTuple() rather
than directly in the loop, because that will also ensure that both
principal code paths through ExecHashJoinOuterGetTuple() will do a
CHECK_FOR_INTERRUPTS, which seems like a good idea to avoid surprises.

Back-patch to all supported branches.

Tom Lane and Thomas Munro

Discussion: https://postgr.es/m/6044.1487121720@sss.pgh.pa.us

Commit 906bfcad adjusted the syntax synopsis for UPDATE, but missed
the fact that the INSERT synopsis now contains a duplicate of that.

In passing, improve wording and markup about using a table alias to
dodge the conflict with use of "excluded" as a special table name.

It wouldn't complete "TO" after the variable name, which is certainly
minor enough.  But since we do complete "TO" after "SET variable ...",
and since this case used to work pre-9.6, I think this is a bug.

Also, fix the query used to collect the variable names; whoever last
touched it evidently didn't understand how the pieces are supposed
to fit together.  It accidentally worked anyway, because readline
ignores irrelevant completions, but it was randomly unlike the ones
around it, and could be a source of actual bugs if someone copied
it as a prototype for another query.

Jeff Janes noted that the error cursor position shown for some errors
would vary when operator_precedence_warning is turned on.  We'd prefer
that option to have no undocumented effects, so this isn't desirable.
To fix, make sure that an AEXPR_PAREN node has the same exprLocation
as its child node.

(Note: it would be a little cheaper to use @2 here instead of an
exprLocation call, but there are cases where that wouldn't produce
the identical answer, so don't do it like that.)

Back-patch to 9.5 where this feature was introduced.

Discussion: https://postgr.es/m/CAMkU=1ykK+VhhcQ4Ky8KBo9FoaUJH3f3rDQB8TkTXi-ZsBRUkQ@mail.gmail.com

In combination with 569174f1, which
taught the btree AM how to perform parallel index scans, this allows
parallel index scan plans on btree indexes.  This infrastructure
should be general enough to support parallel index scans for other
index AMs as well, if someone updates them to support parallel
scans.

Amit Kapila, reviewed and tested by Anastasia Lubennikova, Tushar
Ahuja, and Haribabu Kommi, and me.