I think they're pretty much release-quality now.

I found that half a dozen (nearly 5%) of our AllocSetContextCreate calls
had typos in the context-sizing parameters.  While none of these led to
especially significant problems, they did create minor inefficiencies,
and it's now clear that expecting people to copy-and-paste those calls
accurately is not a great idea.  Let's reduce the risk of future errors
by introducing single macros that encapsulate the common use-cases.
Three such macros are enough to cover all but two special-purpose contexts;
those two calls can be left as-is, I think.

While this patch doesn't in itself improve matters for third-party
extensions, it doesn't break anything for them either, and they can
gradually adopt the simplified notation over time.

In passing, change TopMemoryContext to use the default allocation
parameters.  Formerly it could only be extended 8K at a time.  That was
probably reasonable when this code was written; but nowadays we create
many more contexts than we did then, so that it's not unusual to have a
couple hundred K in TopMemoryContext, even without considering various
dubious code that sticks other things there.  There seems no good reason
not to let it use growing blocks like most other contexts.

Back-patch to 9.6, mostly because that's still close enough to HEAD that
it's easy to do so, and keeping the branches in sync can be expected to
avoid some future back-patching pain.  The bugs fixed by these changes
don't seem to be significant enough to justify fixing them further back.

Discussion: <21072.1472321324@sss.pgh.pa.us>

This has been requested a few times, but the use-case for it was never
entirely clear.  The reason for adding it now is that transmission of
error reports from parallel workers fails when NLS is active, because
pq_parse_errornotice() wrongly assumes that the existing severity field
is nonlocalized.  There are other ways we could have fixed that, but the
other options were basically kluges, whereas this way provides something
that's at least arguably a useful feature along with the bug fix.

Per report from Jakob Egger.  Back-patch into 9.6, because otherwise
parallel query is essentially unusable in non-English locales.  The
problem exists in 9.5 as well, but we don't want to risk changing
on-the-wire behavior in 9.5 (even though the possibility of new error
fields is specifically called out in the protocol document).  It may
be sufficient to leave the issue unfixed in 9.5, given the very limited
usefulness of pq_parse_errornotice in that version.

Discussion: <A88E0006-13CB-49C6-95CC-1A77D717213C@eggerapps.at>

HandleParallelMessages leaked memory into the caller's context.  Since it's
called from ProcessInterrupts, there is basically zero certainty as to what
CurrentMemoryContext is, which means we could be leaking into long-lived
contexts.  Over the processing of many worker messages that would grow to
be a problem.  Things could be even worse than just a leak, if we happened
to service the interrupt while ErrorContext is current: elog.c thinks it
can reset that on its own whim, possibly yanking storage out from under
HandleParallelMessages.

Give HandleParallelMessages its own dedicated context instead, which we can
reset during each call to ensure there's no accumulation of wasted memory.

Discussion: <16610.1472222135@sss.pgh.pa.us>

The guiding principle for the last few patches in this area apparently
involved throwing darts.

Cosmetic only, but back-patch to 9.6 because there is no reason for
9.6 and HEAD to diverge yet in this file.

Copy the palloc'd strings into the correct context, ie ErrorContext
not wherever the source ErrorData is.  This would be a large bug,
except that it appears that all catchers of thrown errors do either
EmitErrorReport or CopyErrorData before doing anything that would
cause transient memory contexts to be cleaned up.  Still, it's wrong
and it will bite somebody someday.

Fix failure to copy cursorpos and internalpos.

Utter the appropriate incantations involving recursion_depth, so that
we'll behave sanely if we get an error inside pstrdup.  (In general,
the body of this function ought to act like, eg, errdetail().)

Per code reading induced by Jakob Egger's report.

The previous coding here was capable of adding a "parallel worker" context
line to errors that were not, in fact, returned from a parallel worker.
Instead of using an errcontext callback to add that annotation, just paste
it onto the message by hand; this looks uglier but is more reliable.

Discussion: <19757.1472151987@sss.pgh.pa.us>

You can use ALTER FOREIGN TABLE SET WITH OIDS on a foreign table, but the
oid column read out as zeros, because the postgres_fdw didn't know about
it. Teach postgres_fdw how to fetch it.

Etsuro Fujita, with an additional test case by me.

Discussion: <56E90A76.5000503@lab.ntt.co.jp>

Commit f0c7b789 added a test case in case.sql that creates and then drops
both an '=' operator and the type it's for.  Given the right timing, that
can cause a "cache lookup failed for type" failure in concurrent sessions,
which see the '=' operator as a potential match for '=' in a query, but
then the type is gone by the time they inquire into its properties.
It might be nice to make that behavior more robust someday, but as a
back-patchable solution, adjust the new test case so that the operator
is never visible to other sessions.  Like the previous commit, back-patch
to all supported branches.

Discussion: <5983.1471371667@sss.pgh.pa.us>

When there is an identifiable REPLICA IDENTITY index on the target table,
heap_update leaks the id_attrs bitmapset.  That's not many bytes, but it
adds up over enough rows, since the code typically runs in a query-lifespan
context.  Bug introduced in commit e55704d8, which did a rather poor job
of cloning the existing use-pattern for RelationGetIndexAttrBitmap().

Per bug #14293 from Zhou Digoal.  Back-patch to 9.4 where the bug was
introduced.

Report: <20160824114320.15676.45171@wrigleys.postgresql.org>

Reported-by: Alexander Law

Author: Alexander Law

Backpatch-through: 9.6

Etsuro Fujita

ExecReScanAgg's check for whether it could re-use a previously calculated
hashtable neglected the possibility that the Agg node might reference
PARAM_EXEC Params that are not referenced by its input plan node.  That's
okay if the Params are in upper tlist or qual expressions; but if one
appears in aggregate input expressions, then the hashtable contents need
to be recomputed when the Param's value changes.

To avoid unnecessary performance degradation in the case of a Param that
isn't within an aggregate input, add logic to the planner to determine
which Params are within aggregate inputs.  This requires a new field in
struct Agg, but fortunately we never write plans to disk, so this isn't
an initdb-forcing change.

Per report from Jeevan Chalke.  This has been broken since forever,
so back-patch to all supported branches.

Andrew Gierth, with minor adjustments by me

Report: <CAM2+6=VY8ykfLT5Q8vb9B6EbeBk-NGuLbT6seaQ+Fq4zXvrDcA@mail.gmail.com>

Accidentally added in 8b65cf4c.

Pointed out by Álvaro Herrera

From: Alexander Law <exclusion@gmail.com>

Oversight in commit 9132c014.

Every program having -lpgfeutils in LDFLAGS must have this dependency,
whether or not the program uses a libpgfeutils symbol.  Back-patch to
9.6, where libpgfeutils was introduced.

With Asserts off, these variables are set but never used, resulting
in warnings from pickier compilers.  Fix that with our standard solution.
Per report from Jeff Janes.

AF_INET is apparently defined in something that's pulled in automatically
on Linux, but the buildfarm says that's not true everywhere.  Comparing
to network_gist.c suggests that including <sys/socket.h> ought to fix it,
and the POSIX standard concurs.

This seems to offer significantly better search performance than the
existing GiST opclass for inet/cidr, at least on data with a wide mix
of network mask lengths.  (That may suggest that the data splitting
heuristics in the GiST opclass could be improved.)

Emre Hasegeli, with mostly-cosmetic adjustments by me

Discussion: <CAE2gYzxtth9qatW_OAqdOjykS0bxq7AYHLuyAQLPgT7H9ZU0Cw@mail.gmail.com>

If you have previously pinned a segment and decide that you don't
actually want to keep it around until shutdown, this new API lets you
remove the pin.  This is pretty trivial except on Windows, where it
requires closing the duplicate handle that was used to implement the
pin.

Thomas Munro and Amit Kapila, reviewed by Amit Kapila and by me.

Kyotaro Horiguchi

Discussion: dcc4113d-1eda-4f60-d1c5-f50eee160bad@gmail.com

Author: Alexander Law <exclusion@gmail.com>

Backpatch-through: 9.6

Previously, the spgSplitTuple action could only create a new upper tuple
containing a single labeled node.  This made it useless for opclasses
that prefer to work with fixed sets of nodes (labeled or otherwise),
which meant that restrictive prefixes could not be used with such
node definitions.  Change the output field set for the choose() method
to allow it to specify any valid node set for the new upper tuple,
and to specify which of these nodes to place the modified lower tuple in.

In addition to its primary use for fixed node sets, this feature could
allow existing opclasses that use variable node sets to skip a separate
spgAddNode action when splitting a tuple, by setting up the node needed
for the incoming value as part of the spgSplitTuple action.  However, care
would have to be taken to add the extra node only when it would not make
the tuple bigger than before.  (spgAddNode can enlarge the tuple,
spgSplitTuple can't.)

This is a prerequisite for an upcoming SP-GiST inet opclass, but is
being committed separately to increase the visibility of the API change.

In passing, improve the documentation about the traverse-values feature
that was added by commit ccd6eb49.

Emre Hasegeli, with cosmetic adjustments and documentation rework by me

Discussion: <CAE2gYzxtth9qatW_OAqdOjykS0bxq7AYHLuyAQLPgT7H9ZU0Cw@mail.gmail.com>

Add a variant of txid_current() that returns NULL if no transaction ID
is assigned.  This version can be used even on a standby server,
although it will always return NULL since no transaction IDs can be
assigned during recovery.

Craig Ringer, per suggestion from Jim Nasby.  Reviewed by Petr Jelinek
and by me.

Erik Rijkers

Merge several copies of "copy an inet value and adjust the mask length"
code to create a single, conveniently C-callable function.  This function
is exported for future use by inet SPGiST support, but it's good cleanup
anyway since we had three slightly-different-for-no-good-reason copies.

(Extracted from a larger patch, to separate new code from refactoring
of old code)

Emre Hasegeli

Reported-by: Jeff Janes

Backpatch-through: 9.6

Due to an error in the abbreviated key abort logic, the most recently
processed SortTuple could be incorrectly marked NULL, resulting in an
incorrect final sort order.

In the worst case, this could result in a corrupt btree index, which
would need to be rebuild using REINDEX.  However, abbrevation doesn't
abort very often, not all data types use it, and only one tuple would
end up in the wrong place, so the practical impact of this mistake may
be somewhat limited.

Report and patch by Peter Geoghegan.

Dimitry Ivanov spotted a typo, and I added a bit of wordsmithing.

Remove the plpgsql wrapping that hides the context.  So now the test
will fail if the work doesn't actually happen in a parallel worker.  Run
the test in its own test group to ensure it won't run out of resources
for that.

More fallout from commit a00c5831.  Pointed out by Michael Paquier.

It is redundant with appendConnStrVal(), which became an extern function
in commit 41f18f02.  This changes the
handling of out-of-memory and of certain inputs for which quoting is
optional, but pg_basebackup has no need for unusual treatment thereof.

Fallout from commit a00c5831.  Per buildfarm.

The original coding here was not nearly careful enough about quoting
special characters, and it didn't get corner cases right for constructing
the pg_ctl path either.  Use join_path_components() and appendShellString()
to do it honestly, so that the string will more likely work if blindly
copied-and-pasted.

While at it, teach appendShellString() not to quote strings that clearly
don't need it, so that the output from initdb doesn't become uglier than
it was before in typical cases where quoting is not needed.

Ryan Murphy, reviewed by Michael Paquier and myself

Discussion: <CAHeEsBeAe1FeBypT3E8R1ZVZU0e8xv3A-7BHg6bEOi=jZny2Uw@mail.gmail.com>

This might have been too much of a foot-gun before 9.6, but with the
new commands-end-at-semicolons parsing rule, the only way to get an
empty query into a script is to explicitly write an extra ";".
So we may as well allow the case.

Fabien Coelho

Patch: <alpine.DEB.2.20.1607090922170.3412@sto>

In particular, left join to pg_authid so that rows in pg_stat_activity
don't disappear if the session's owning user has been dropped.
Also convert a few joins to pg_database to left joins, in the same spirit,
though that case might be harder to hit.  We were doing this in other
views already, so it was a bit inconsistent that these views didn't.

Oskari Saarenmaa, with some further tweaking by me

Discussion: <56E87CD8.60007@ohmu.fi>

Obvious brain fade in set_rel_consider_parallel().  Noticed it while
adjusting the adjacent RTE_FUNCTION case.

In 9.6, also make the code look more like what I just did in HEAD
by removing the unnecessary function_rte_parallel_ok subroutine
(it does nothing that expression_tree_walker wouldn't do).

We need to scan the whole parse tree for parallel-unsafe functions.
If there are none, we'll later need to determine whether particular
subtrees contain any parallel-restricted functions.  The previous coding
retained no knowledge from the first scan, even though this is very
wasteful in the common case where the query contains only parallel-safe
functions.  We can bypass all of the later scans by remembering that fact.
This provides a small but measurable speed improvement when the case
applies, and shouldn't cost anything when it doesn't.

Patch by me, reviewed by Robert Haas

Discussion: <3740.1471538387@sss.pgh.pa.us>