Oops, meant to change the comment in writeTimeLineHistory.
Ensure recovery pause feature doesn't pause unless users can connect.

If we're not in hot standby mode, then there's no way for users to connect
to reset the recoveryPause flag, so we shouldn't pause.  The code was aware
of this but the test to see if pausing was safe was seriously inadequate:
it wasn't paying attention to reachedConsistency, and besides what it was
testing was that we could legally enter hot standby, not that we have
done so.  Get rid of that in favor of checking LocalHotStandbyActive,
which because of the coding in CheckRecoveryConsistency is tantamount to
checking that we have told the postmaster to enter hot standby.

Also, move the recoveryPausesHere() call that reacts to asynchronous
recoveryPause requests so that it's not in the middle of application of a
WAL record.  I put it next to the recoveryStopsHere() call --- in future
those are going to need to interact significantly, so this seems like a
good waystation.

Also, don't bother trying to read another WAL record if we've already
decided not to continue recovery.  This was no big deal when the code was
written originally, but now that reading a record might entail actions like
fetching an archive file, it seems a bit silly to do it like that.

Per report from Jeff Janes and subsequent discussion.  The pause feature
needs quite a lot more work, but this gets rid of some indisputable bugs,
and seems safe enough to back-patch.
Update comment at top of index_create

I neglected to update it in commit f4c4335.

Michael Paquier
Fix intermittent crash in DROP INDEX CONCURRENTLY.

When deleteOneObject closes and reopens the pg_depend relation,
we must see to it that the relcache pointer held by the calling function
(typically performMultipleDeletions) is updated.  Usually the relcache
entry is retained so that the pointer value doesn't change, which is why
the problem had escaped notice ... but after a cache flush event there's
no guarantee that the same memory will be reassigned.  To fix, change
the recursive functions' APIs so that we pass around a "Relation *"
not just "Relation".

Per investigation of occasional buildfarm failures.  This is trivial
to reproduce with -DCLOBBER_CACHE_ALWAYS, which points up the sad
lack of any buildfarm member running that way on a regular basis.
Background worker processes

Background workers are postmaster subprocesses that run arbitrary
user-specified code.  They can request shared memory access as well as
backend database connections; or they can just use plain libpq frontend
database connections.

Modules listed in shared_preload_libraries can register background
workers in their _PG_init() function; this is early enough that it's not
necessary to provide an extra GUC option, because the necessary extra
resources can be allocated early on.  Modules can install more than one
bgworker, if necessary.

Care is taken that these extra processes do not interfere with other
postmaster tasks: only one such process is started on each ServerLoop
iteration.  This means a large number of them could be waiting to be
started up and postmaster is still able to quickly service external
connection requests.  Also, shutdown sequence should not be impacted by
a worker process that's reasonably well behaved (i.e. promptly responds
to termination signals.)

The current implementation lets worker processes specify their start
time, i.e. at what point in the server startup process they are to be
started: right after postmaster start (in which case they mustn't ask
for shared memory access), when consistent state has been reached
(useful during recovery in a HOT standby server), or when recovery has
terminated (i.e. when normal backends are allowed).

In case of a bgworker crash, actions to take depend on registration
data: if shared memory was requested, then all other connections are
taken down (as well as other bgworkers), just like it were a regular
backend crashing.  The bgworker itself is restarted, too, within a
configurable timeframe (which can be configured to be never).

More features to add to this framework can be imagined without much
effort, and have been discussed, but this seems good enough as a useful
unit already.

An elementary sample module is supplied.

Author: Álvaro Herrera

This patch is loosely based on prior patches submitted by KaiGai Kohei,
and unsubmitted code by Simon Riggs.

Reviewed by: KaiGai Kohei, Markus Wanner, Andres Freund,
Heikki Linnakangas, Simon Riggs, Amit Kapila
Improve pl/pgsql to support composite-type expressions in RETURN.

For some reason lost in the mists of prehistory, RETURN was only coded to
allow a simple reference to a composite variable when the function's return
type is composite.  Allow an expression instead, while preserving the
efficiency of the original code path in the case where the expression is
indeed just a composite variable's name.  Likewise for RETURN NEXT.

As is true in various other places, the supplied expression must yield
exactly the number and data types of the required columns.  There was some
discussion of relaxing that for pl/pgsql, but no consensus yet, so this
patch doesn't address that.

Asif Rehman, reviewed by Pavel Stehule
Clarify that COPY FREEZE is not a hard rule.
Remove message when FREEZE not honoured,
clarify reasons in comments and docs.
Optimize COPY FREEZE with CREATE TABLE also.

Jeff Davis, additional test by me
Correct xmax test for COPY FREEZE
Improve pg_upgrade's status display

Pg_upgrade displays file names during copy and database names during
dump/restore.  Andrew Dunstan identified three bugs:

*  long file names were being truncated to 60 _leading_ characters, which
   often do not change for long file names

*  file names were truncated to 60 characters in log files

*  carriage returns were being output to log files

This commit fixes these --- it prints 60 _trailing_ characters to the
status display, and full path names without carriage returns to log
files.  It also suppresses status output to the log file unless verbose
mode is used.
Update iso.org page link

The old one is responding with 404.
Support automatically-updatable views.

This patch makes "simple" views automatically updatable, without the need
to create either INSTEAD OF triggers or INSTEAD rules.  "Simple" views
are those classified as updatable according to SQL-92 rules.  The rewriter
transforms INSERT/UPDATE/DELETE commands on such views directly into an
equivalent command on the underlying table, which will generally have
noticeably better performance than is possible with either triggers or
user-written rules.  A view that has INSTEAD OF triggers or INSTEAD rules
continues to operate the same as before.

For the moment, security_barrier views are not considered simple.
Also, we do not support WITH CHECK OPTION.  These features may be
added in future.

Dean Rasheed, reviewed by Amit Kapila
Fix assorted bugs in privileges-for-types patch.

Commit 729205571e81b4767efc42ad7beb53663e08d1ff added privileges on data
types, but there were a number of oversights.  The implementation of
default privileges for types missed a few places, and pg_dump was
utterly innocent of the whole concept.  Per bug #7741 from Nathan Alden,
and subsequent wider investigation.
Fix the tracking of min recovery point timeline.

Forgot to update it at the right place. Also, consider checkpoint record
that switches to new timelne to be on the new timeline.

This fixes erroneous "requested timeline 2 does not contain minimum recovery
point" errors, pointed out by Amit Kapila while testing another patch.
Update minimum recovery point on truncation.

If a file is truncated, we must update minRecoveryPoint. Once a file is
truncated, there's no going back; it would not be safe to stop recovery
at a point earlier than that anymore.

Per report from Kyotaro HORIGUCHI. Backpatch to 8.4. Before that,
minRecoveryPoint was not updated during recovery at all.
doc: Remove blastwave.org link

Apparently, this service has been dead since 2008.
Fix pg_upgrade -O/-o options

Fix previous commit that added synchronous_commit=off, but broke -O/-o
due to missing space in argument passing.

Backpatch to 9.2.
Add mode where contrib installcheck runs each module in a separately named database.

Normally each module is tested in a database named contrib_regression,
which is dropped and recreated at the beginhning of each pg_regress run.
This new mode, enabled by adding USE_MODULE_DB=1 to the make command
line, runs most modules in a database with the module name embedded in
it.

This will make testing pg_upgrade on clusters with the contrib modules
a lot easier.

Second attempt at this, this time accomodating make versions older
than 3.82.

Still to be done: adapt to the MSVC build system.

Backpatch to 9.0, which is the earliest version it is reasonably
possible to test upgrading from.
Consistency check should compare last record replayed, not last record read.

EndRecPtr is the last record that we've read, but not necessarily yet
replayed. CheckRecoveryConsistency should compare minRecoveryPoint with the
last replayed record instead. This caused recovery to think it's reached
consistency too early.

Now that we do the check in CheckRecoveryConsistency correctly, we have to
move the call of that function to after redoing a record. The current place,
after reading a record but before replaying it, is wrong. In particular, if
there are no more records after the one ending at minRecoveryPoint, we don't
enter hot standby until one extra record is generated and read by the
standby, and CheckRecoveryConsistency is called. These two bugs conspired
to make the code appear to work correctly, except for the small window
between reading the last record that reaches minRecoveryPoint, and
replaying it.

In the passing, rename recoveryLastRecPtr, which is the last record
replayed, to lastReplayedEndRecPtr. This makes it slightly less confusing
with replayEndRecPtr, which is the last record read that we're about to
replay.

Original report from Kyotaro HORIGUCHI, further diagnosis by Fujii Masao.
Backpatch to 9.0, where Hot Standby subtly changed the test from
"minRecoveryPoint < EndRecPtr" to "minRecoveryPoint <= EndRecPtr". The
former works because where the test is performed, we have always read one
more record than we've replayed.
Fix pg_upgrade for invalid indexes

All versions of pg_upgrade upgraded invalid indexes caused by CREATE
INDEX CONCURRENTLY failures and marked them as valid.  The patch adds a
check to all pg_upgrade versions and throws an error during upgrade or
--check.

Backpatch to 9.2, 9.1, 9.0.  Patch slightly adjusted.