Also fill in the previously empty "major enhancements" list.  YMMV as to
which items should make the cut, but it's past time we had something more
than a placeholder here.

(I meant to get this done before beta2 was wrapped, but got distracted by
PDF build problems.  Better late than never.)

These were discussed in three different sections of the manual, which
unsurprisingly had diverged over time; and the descriptions of individual
variables lacked stylistic consistency even within each section (and
frequently weren't in very good English anyway).  Clean up the mess, and
remove some of the redundant information in hopes that future additions
will be less likely to re-introduce inconsistency.  For instance I see
no need for maintenance.sgml to include its very own list of all the
autovacuum storage parameters, especially since that list was already
incomplete.

In commit 5d1ff6bd I added some logic to
relcache.c to try to ensure that the regression tests would fail if we
made a mistake about which relations belong in the relcache init files.
I'm quite sure I tested that, but I must have done so only for the
non-shared-catalog case, because a report from Adam Brightwell showed that
the regression tests still pass just fine if we bollix the shared-catalog
init file in the way this code was supposed to catch.  The reason is that
that file gets loaded before we do client authentication, so the WARNING
is not sent to the client, only to the postmaster log, where it's far too
easily missed.

The least Rube Goldbergian answer to this is to put an Assert(false)
after the elog(WARNING).  That will certainly get developers' attention,
while not breaking production builds' ability to recover from corner
cases with similar symptoms.

Since this is only of interest to developers, there seems no need for
a back-patch, even though the previous commit went into all branches.

Add a new flag, consider_parallel, to each RelOptInfo, indicating
whether a plan for that relation could conceivably be run inside of
a parallel worker.  Right now, we're pretty conservative: for example,
it might be possible to defer applying a parallel-restricted qual
in a worker, and later do it in the leader, but right now we just
don't try to parallelize access to that relation.  That's probably
the right decision in most cases, anyway.

Using the new flag, generate parallel sequential scan plans for plain
baserels, meaning that we now have parallel sequential scan in
PostgreSQL.  The logic here is pretty unsophisticated right now: the
costing model probably isn't right in detail, and we can't push joins
beneath Gather nodes, so the number of plans that can actually benefit
from this is pretty limited right now.  Lots more work is needed.
Nevertheless, it seems time to enable this functionality so that all
this code can actually be tested easily by users and developers.

Note that, if you wish to test this functionality, it will be
necessary to set max_parallel_degree to a value greater than the
default of 0.  Once a few more loose ends have been tidied up here, we
might want to consider changing the default value of this GUC, but
I'm leaving it alone for now.

Along the way, fix a bug in cost_gather: the previous coding thought
that a Gather node's transfer overhead should be costed on the basis of
the relation size rather than the number of tuples that actually need
to be passed off to the leader.

Patch by me, reviewed in earlier versions by Amit Kapila.

In addition, this path fills in a number of missing bits and pieces in
the parallel infrastructure.  Paths and plans now have a parallel_aware
flag indicating whether whatever parallel-aware logic they have should
be engaged.  It is believed that we will need this flag for a number of
path/plan types, not just sequential scans, which is why the flag is
generic rather than part of the SeqScan structures specifically.
Also, execParallel.c now gives parallel nodes a chance to initialize
their PlanState nodes from the DSM during parallel worker startup.

Amit Kapila, with a fair amount of adjustment by me.  Review of previous
patch versions by Haribabu Kommi and others.

I dunno how commit 3bd909b2 missed
this, but it evidently did.

Commit 8457d0be introduced an example which, while not incorrect,
failed to exhibit the behavior it meant to describe, as a result of omitting
an E'' prefix that needed to be there.  Noticed and fixed by Peter Geoghegan.

I (tgl) failed to resist the temptation to wordsmith nearby text a bit
while at it.

Per buildfarm member pademelon.

In commit a5ec86a7 I wrote a quick hack
that reduced the number of TeX string pool entries created while converting
our documentation to PDF form.  That held the fort for awhile, but as of
HEAD we're back up against the same limitation.  It turns out that the
original coding of \FlowObjectSetup actually results in *three* string pool
entries being generated for every "flow object" (that is, potential
cross-reference target) in the documentation, and my previous hack only got
rid of one of them.  With a little more care, we can reduce the string
count to one per flow object plus one per actually-cross-referenced flow
object (about 115000 + 5000 as of current HEAD); that should work until
the documentation volume roughly doubles from where it is today.

As a not-incidental side benefit, this change also causes pdfjadetex to
stop emitting unreferenced hyperlink anchors (bookmarks) into the PDF file.
It had been making one willy-nilly for every flow object; now it's just one
per actually-cross-referenced object.  This results in close to a 2X
savings in PDF file size.  We will still want to run the output through
"jpdftweak" to get it to be compressed; but we no longer need removal of
unreferenced bookmarks, so we might be able to find a quicker tool for
that step.

Although the failure only affects HEAD and US-format output at the moment,
9.5 cannot be more than a few pages short of failing likewise, so it
will inevitably fail after a few rounds of minor-version release notes.
I don't have a lot of faith that we'll never hit the limit in the older
branches; and anyway it would be nice to get rid of jpdftweak across the
board.  Therefore, back-patch to all supported branches.

Adjust to account for 5fc4c26d.

Etsuro Fujita

The patches committed as 6e71dd7c
and 3a1f8611 were developed in
parallel but dependent on each other in a way that I failed to
notice.

This patch to fix the problem was prepared by Amit Kapila.

This is unreachable for multiple reasons, but per Amit Kapila the
Windows compiler he is using still thinks we can get there.

Author: Peter Geoghegan and Andres Freund
Discussion: CAM3SWZScpWzQ-7EJC77vwqzZ1GO8GNmURQ1QqDQ3wRn7AbW1Cg@mail.gmail.com,
    CAHGQGwFUCWwSU7dtc2aRdRk73ztyr_jY5cPOyts+K8xKJ92X4Q@mail.gmail.com
Backpatch: 9.5, where UPSERT was introduced

By accident the replication origin was not set properly in
DecodeCommit(). That's bad because the origin is passed to the output
plugins origin filter, and accessible from the output plugin via
ReorderBufferTXN->origin_id.  Accessing the origin of individual changes
worked before the fix, which is why this wasn't notices earlier.

Reported-By: Craig Ringer
Author: Craig Ringer
Discussion: CAMsr+YFhBJLp=qfSz3-J+0P1zLkE8zNXM2otycn20QRMx380gw@mail.gmail.com
Backpatch: 9.5, where replication origins where introduced

At least OpenBSD, NetBSD, and Windows don't support it.  This repairs
pg_ctl for listen_addresses='0.0.0.0' and listen_addresses='::'.  Since
pg_ctl prefers to test a Unix-domain socket, Windows users are most
likely to need this change.  Back-patch to 9.1 (all supported versions).
This could change pg_ctl interaction with loopback-interface firewall
rules.  Therefore, in 9.4 and earlier (released branches), activate the
change only on known-affected platforms.

Reported (bug #13611) and designed by Kondo Yuta.

Reported by both Peter Eisentraunt and Kevin Grittner.

The corresponding "=" operators have been there a long time, and not
having their negators is a bit of a nuisance.

Michael Paquier

Per discussion, the original name was a bit misleading, and
PQsslAttributeNames() seems more apropos.  It's not quite too late to
change this in 9.5, so let's change it while we can.

Also, make sure that the pointer array is const, not only the pointed-to
strings.

Minor documentation wordsmithing while at it.

Lars Kanis, slight adjustments by me

Lookahead and lookbehind constraints aren't allowed to contain backrefs,
and parentheses within them are always considered non-capturing.  Or so
says the manual.  But the regexp parser forgot about these rules once
inside a parenthesized subexpression, so that constructs like (\w)(?=(\1))
were accepted (but then not correctly executed --- a case like this acted
like (\w)(?=\w), without any enforcement that the two \w's match the same
text).  And in (?=((foo))) the innermost parentheses would be counted as
capturing parentheses, though no text would ever be captured for them.

To fix, properly pass down the "type" argument to the recursive invocation
of parse().

Back-patch to all supported branches; it was agreed that silent
misexecution of such patterns is worse than throwing an error, even though
new errors in minor releases are generally not desirable.

Without this, MacOS gcc version 4.2.1 isn't convinced.

Jeff Janes

Commit 4a4e6893, which introduced this
mechanism, failed to account for the fact that the RECORD pseudo-type
uses transient typmods that are only meaningful within a single
backend.  Transferring such tuples without modification between two
cooperating backends does not work.  This commit installs a system
for passing the tuple descriptors over the same shm_mq being used to
send the tuples themselves.  The two sides might not assign the same
transient typmod to any given tuple descriptor, so we must also
substitute the appropriate receiver-side typmod for the one used by
the sender.  That adds some CPU overhead, but still seems better than
being unable to pass records between cooperating parallel processes.

Along the way, move the logic for handling multiple tuple queues from
tqueue.c to nodeGather.c; tqueue.c now provides a TupleQueueReader,
which reads from a single queue, rather than a TupleQueueFunnel, which
potentially reads from multiple queues.  This change was suggested
previously as a way to make sure that nodeGather.c rather than tqueue.c
had policy control over the order in which to read from queues, but
it wasn't clear to me until now how good an idea it was.  typmod
mapping needs to be performed separately for each queue, and it is
much simpler if the tqueue.c code handles that and leaves multiplexing
multiple queues to higher layers of the stack.

Noted by Kyotaro Horiguchi, who also reviewed the previous patch, but
I failed to notice his review before committing.

This introduces a simple encoding scheme to produce abbreviated keys:
pack as many bytes of each UUID as will fit into a Datum.  On
little-endian machines, a byteswap is also performed; the abbreviated
comparator can therefore just consist of a simple 3-way unsigned integer
comparison.

The purpose of this change is to speed up sorting data on a column
of type UUID.

Peter Geoghegan

With include_realm=1 being set down in parse_hba_auth_opt, if multiple
options are passed on the pg_hba line, such as:

host all     all    0.0.0.0/0    gss include_realm=0 krb_realm=XYZ.COM

We would mistakenly reset include_realm back to 1.  Instead, we need to
set include_realm=1 up in parse_hba_line, prior to parsing any of the
additional options.

Discovered by Jeff McCormick during testing.

Bug introduced by 9a088417.

Back-patch to 9.5

Previously, negative values were always displayed in bytes, regardless
of how large they were.

Adrian Vondendriesch, reviewed by Julien Rouhaud and myself

Thomas Munro and Robert Haas, reviewed by Haribabu Kommi

The jsonb_path_ops code calculated hash values inconsistently in some cases
involving nested arrays and objects.  This would result in queries possibly
not finding entries that they should find, when using a jsonb_path_ops GIN
index for the search.  The problem cases involve JSONB values that contain
both scalars and sub-objects at the same nesting level, for example an
array containing both scalars and sub-arrays.  To fix, reset the current
stack->hash after processing each value or sub-object, not before; and
don't try to be cute about the outermost level's initial hash.

Correcting this means that existing jsonb_path_ops indexes may now be
inconsistent with the new hash calculation code.  The symptom is the same
--- searches not finding entries they should find --- but the specific
rows affected are likely to be different.  Users will need to REINDEX
jsonb_path_ops indexes to make sure that all searches work as expected.

Per bug #13756 from Daniel Cheng.  Back-patch to 9.4 where the faulty
logic was introduced.

Previously, plpython was in the habit of allocating a lot of stuff in
TopMemoryContext, and it was very slipshod about making sure that stuff
got cleaned up; in particular, use of TopMemoryContext as fn_mcxt for
function calls represents an unfixable leak, since we generally don't
know what the called function might have allocated in fn_mcxt.  This
results in session-lifespan leakage in certain usage scenarios, as for
example in a case reported by Ed Behn back in July.

To fix, get rid of all the retail allocations in TopMemoryContext.
All long-lived allocations are now made in sub-contexts that are
associated with specific objects (either pl/python procedures, or
Python-visible objects such as cursors and plans).  We can clean these
up when the associated object is deleted.

I went so far as to get rid of PLy_malloc completely.  There were a
couple of places where it could still have been used safely, but on
the whole it was just an invitation to bad coding.

Haribabu Kommi, based on a draft patch by Heikki Linnakangas;
some further work by me

Up until now, the total amount of data that could be passed to a
background worker at startup was one datum, which can be a small as
4 bytes on some systems.  That's enough to pass a dsm_handle or an
array index, but not much else.  Add a bgw_extra flag to the
BackgroundWorker struct, allowing up to 128 bytes to be passed to
a new worker on any platform.

Use this to fix a problem I recently discovered with the parallel
context machinery added in 9.5: the master assigns each worker an
array index, and each worker subsequently assigns itself an array
index, and there's nothing to guarantee that the two sets of indexes
match, leading to chaos.

Normally, I would not back-patch the change to add bgw_extra, since it
is basically a feature addition.  However, since 9.5 is still in beta
and there seems to be no other sensible way to repair the broken
parallel context machinery, back-patch to 9.5.  Existing background
worker code can ignore the bgw_extra field without a problem, but
might need to be recompiled since the structure size has changed.

Report and patch by me.  Review by Amit Kapila.

Rather than filling a temporary array and then copying values to the
output array, we can generate the required random permutation in-place
using the Fisher-Yates shuffle algorithm.  This is shorter as well as
more efficient than before.  It's pretty unlikely that anyone would
notice a speed improvement, but shorter code is better.

Nathan Wagner, edited a bit by me

The preferred spelling was changed from FORCE QUOTE to FORCE_QUOTE and
the like, but some code was still referring to the old spellings.

Rather than relying on other extensions to be available for installation,
let's just add some test objects to the postgres_fdw extension itself
within the regression script.

The user can whitelist specified extension(s) in the foreign server's
options, whereupon we will treat immutable functions and operators of those
extensions as candidates to be sent for remote execution.

Whitelisting an extension in this way basically promises that the extension
exists on the remote server and behaves compatibly with the local instance.
We have no way to prove that formally, so we have to rely on the user to
get it right.  But this seems like something that people can usually get
right in practice.

We might in future allow functions and operators to be whitelisted
individually, but extension granularity is a very convenient special case,
so it got done first.

The patch as-committed lacks any regression tests, which is unfortunate,
but introducing dependencies on other extensions for testing purposes
would break "make installcheck" scenarios, which is worse.  I have some
ideas about klugy ways around that, but it seems like material for a
separate patch.  For the moment, leave the problem open.

Paul Ramsey, hacked up a bit more by me

Peter Geoghegan

If the join problem's entire ORDER BY clause can be pushed to the
remote server, consider a path that adds this ORDER BY clause.  If
use_remote_estimate is on, we cost this path using an additional
remote EXPLAIN.  If not, we just estimate that the path costs 20%
more, which is intended to be large enough that we won't request a
remote sort when it's not helpful, but small enough that we'll have
the remote side do the sort when in doubt.  In some cases, the remote
sort might actually be free, because the remote query plan might
happen to produce output that is ordered the way we need, but without
remote estimates we have no way of knowing that.

It might also be useful to request sorted output from the remote side
if it enables an efficient merge join, but this patch doesn't attempt
to handle that case.

Ashutosh Bapat with revisions by me.  Also reviewed by Fabrízio de Royes
Mello and Jeevan Chalke.

Standard-conforming literals have been the default for long enough that
it no longer seems necessary to go out of our way to tell people to write
regex escapes illegibly.

Fix some brain fade in commit a2dabf0e: erroneous variable names
in docs, rearrangements that made sentences less clear not more so,
undocumented and poorly-chosen-anyway API behaviors of subroutines,
bad grammar in error messages, copy-and-paste faults.

Albe Laurenz and Tom Lane

Commit a1480ec1 purported to fix the
problems with commit b2ccb5f4, but it
didn't completely fix them.  The problem is that the checks were
performed in the wrong order, leading to a race condition.  If the
sender attached, sent a message, and detached after the receiver
called shm_mq_get_sender and before the receiver called
shm_mq_counterparty_gone, we'd incorrectly return SHM_MQ_DETACHED
before all messages were read.  Repair by reversing the order of
operations, and add a long comment explaining why this new logic is
(hopefully) correct.