Speed up operations on numeric, mostly by avoiding palloc() overhead.

In many functions, a NumericVar was initialized from an input Numeric, to be
passed as input to a calculation function. When the NumericVar is not
modified, the digits array of the NumericVar can point directly to the digits
array in the original Numeric, and we can avoid a palloc() and memcpy(). Add
init_var_from_num() function to initialize a var like that.

Remove dscale argument from get_str_from_var(), as all the callers just
passed the dscale of the variable. That means that the rounding it used to
do was not actually necessary, and get_str_from_var() no longer scribbles on
its input. That makes it safer in general, and allows us to use the new
init_var_from_num() function in e.g numeric_out().

Also modified numericvar_to_int8() to no scribble on its input either. It
creates a temporary copy to avoid that. To compensate, the callers no longer
need to create a temporary copy, so the net # of pallocs is the same, but this
is nicer.

In the passing, use a constant for the number 10 in get_str_from_var_sci(),
when calculating 10^exponent. Saves a palloc() and some cycles to convert
integer 10 to numeric.

Original patch by Kyotaro HORIGUCHI, with further changes by me. Reviewed
by Pavel Stehule.
Don't launch new child processes after we've been told to shut down.

Once we've received a shutdown signal (SIGINT or SIGTERM), we should not
launch any more child processes, even if we get signals requesting such.
The normal code path for spawning backends has always understood that,
but the postmaster's infrastructure for hot standby and autovacuum didn't
get the memo.  As reported by Hari Babu in bug #7643, this could lead to
failure to shut down at all in some cases, such as when SIGINT is received
just before the startup process sends PMSIGNAL_RECOVERY_STARTED: we'd
launch a bgwriter and checkpointer, and then those processes would have no
idea that they ought to quit.  Similarly, launching a new autovacuum worker
would result in waiting till it finished before shutting down.

Also, switch the order of the code blocks in reaper() that detect startup
process crash versus shutdown termination.  Once we've sent it a signal,
we should not consider that exit(1) is surprising.  This is just a cosmetic
fix since shutdown occurs correctly anyway, but better not to log a phony
complaint about startup process crash.

Back-patch to 9.0.  Some parts of this might be applicable before that,
but given the lack of prior complaints I'm not going to worry too much
about older branches.
Avoid bogus "out-of-sequence timeline ID" errors in standby-mode.

When startup process opens a WAL segment after replaying part of it, it
validates the first page on the WAL segment, even though the page it's
really interested in later in the file. As part of the validation, it checks
that the TLI on the page header is >= the TLI it saw on the last page it
read. If the segment contains a timeline switch, and we have already
replayed it, and then re-open the WAL segment (because of streaming
replication got disconnected and reconnected, for example), the TLI check
will fail when the first page is validated. Fix that by relaxing the TLI
check when re-opening a WAL segment.

Backpatch to 9.0. Earlier versions had the same code, but before standby
mode was introduced in 9.0, recovery never tried to re-read a segment after
partially replaying it.

Reported by Amit Kapila, while testing a new feature.
Fix pg_resetxlog to use correct path to postmaster.pid.

Since we've already chdir'd into the data directory, the file should
be referenced as just "postmaster.pid", without prefixing the directory
path.  This is harmless in the normal case where an absolute PGDATA path
is used, but quite dangerous if a relative path is specified, since the
program might then fail to notice an active postmaster.

Reported by Hari Babu.  This got broken in my commit
eb5949d190e80360386113fde0f05854f0c9824d, so patch all active versions.
Applied patch by Chen Huajun <chenhj@cn.fujitsu.com> to make ecpg able to cope
with very long structs.
Remove -Wlogical-op from standard compiler flags

It creates too many warnings with GCC 4.3 and 4.4.
In pg_upgrade, fix a few place that used maloc/free rather than
pg_malloc/pg_free.
In pg_upgrade, simplify function copy_file() by using pg_malloc() and
centralizing error/shutdown code.
Fix SELECT DISTINCT with index-optimized MIN/MAX on inheritance trees.

In a query such as "SELECT DISTINCT min(x) FROM tab", the DISTINCT is
pretty useless (there being only one output row), but nonetheless it
shouldn't fail.  But it could fail if "tab" is an inheritance parent,
because planagg.c's code for fixing up equivalence classes after making the
index-optimized MIN/MAX transformation wasn't prepared to find child-table
versions of the aggregate expression.  The least ugly fix seems to be
to add an option to mutate_eclass_expressions() to skip child-table
equivalence class members, which aren't used anymore at this stage of
planning so it's not really necessary to fix them.  Since child members
are ignored in many cases already, it seems plausible for
mutate_eclass_expressions() to have an option to ignore them too.

Per bug #7703 from Maxim Boguk.

Back-patch to 9.1.  Although the same code exists before that, it cannot
encounter child-table aggregates AFAICS, because the index optimization
transformation cannot succeed on inheritance trees before 9.1 (for lack
of MergeAppend).
Revert patch for taking fewer snapshots.

This reverts commit d573e239f03506920938bf0be56c868d9c3416da, "Take fewer
snapshots".  While that seemed like a good idea at the time, it caused
execution to use a snapshot that had been acquired before locking any of
the tables mentioned in the query.  This created user-visible anomalies
that were not present in any prior release of Postgres, as reported by
Tomas Vondra.  While this whole area could do with a redesign (since there
are related cases that have anomalies anyway), it doesn't seem likely that
any future patch would be reasonably back-patchable; and we don't want 9.2
to exhibit a behavior that's subtly unlike either past or future releases.
Hence, revert to prior code while we rethink the problem.
Add OpenTransientFile, with automatic cleanup at end-of-xact.

Files opened with BasicOpenFile or PathNameOpenFile are not automatically
cleaned up on error. That puts unnecessary burden on callers that only want
to keep the file open for a short time. There is AllocateFile, but that
returns a buffered FILE * stream, which in many cases is not the nicest API
to work with. So add function called OpenTransientFile, which returns a
unbuffered fd that's cleaned up like the FILE* returned by AllocateFile().

This plugs a few rare fd leaks in error cases:

1. copy_file() - fixed by by using OpenTransientFile instead of BasicOpenFile
2. XLogFileInit() - fixed by adding close() calls to the error cases. Can't
   use OpenTransientFile here because the fd is supposed to persist over
   transaction boundaries.
3. lo_import/lo_export - fixed by using OpenTransientFile instead of
   PathNameOpenFile.

In addition to plugging those leaks, this replaces many BasicOpenFile() calls
with OpenTransientFile() that were not leaking, because the code meticulously
closed the file on error. That wasn't strictly necessary, but IMHO it's good
for robustness.

The same leaks exist in older versions, but given the rarity of the issues,
I'm not backpatching this. Not yet, anyway - it might be good to backpatch
later, after this mechanism has had some more testing in master branch.
Add explicit casts in ilist.h's inline functions.

Needed to silence C++ errors, per report from Peter Eisentraut.

Andres Freund
If we don't have a backup-end-location, don't claim we've reached it.

This was apparently a typo, which caused recovery to think that it
immediately reached the end of backup, and allowed the database to start
up too early.

Reported by Jeff Janes. Backpatch to 9.2, where this code was introduced.
Split out rmgr rm_desc functions into their own files

This is necessary (but not sufficient) to have them compilable outside
of a backend environment.
Fix assorted bugs in CREATE/DROP INDEX CONCURRENTLY.

Commit 8cb53654dbdb4c386369eb988062d0bbb6de725e, which introduced DROP
INDEX CONCURRENTLY, managed to break CREATE INDEX CONCURRENTLY via a poor
choice of catalog state representation.  The pg_index state for an index
that's reached the final pre-drop stage was the same as the state for an
index just created by CREATE INDEX CONCURRENTLY.  This meant that the
(necessary) change to make RelationGetIndexList ignore about-to-die indexes
also made it ignore freshly-created indexes; which is catastrophic because
the latter do need to be considered in HOT-safety decisions.  Failure to
do so leads to incorrect index entries and subsequently wrong results from
queries depending on the concurrently-created index.

To fix, add an additional boolean column "indislive" to pg_index, so that
the freshly-created and about-to-die states can be distinguished.  (This
change obviously is only possible in HEAD.  This patch will need to be
back-patched, but in 9.2 we'll use a kluge consisting of overloading the
formerly-impossible state of indisvalid = true and indisready = false.)

In addition, change CREATE/DROP INDEX CONCURRENTLY so that the pg_index
flag changes they make without exclusive lock on the index are made via
heap_inplace_update() rather than a normal transactional update.  The
latter is not very safe because moving the pg_index tuple could result in
concurrent SnapshotNow scans finding it twice or not at all, thus possibly
resulting in index corruption.  This is a pre-existing bug in CREATE INDEX
CONCURRENTLY, which was copied into the DROP code.

In addition, fix various places in the code that ought to check to make
sure that the indexes they are manipulating are valid and/or ready as
appropriate.  These represent bugs that have existed since 8.2, since
a failed CREATE INDEX CONCURRENTLY could leave a corrupt or invalid
index behind, and we ought not try to do anything that might fail with
such an index.

Also fix RelationReloadIndexInfo to ensure it copies all the pg_index
columns that are allowed to change after initial creation.  Previously we
could have been left with stale values of some fields in an index relcache
entry.  It's not clear whether this actually had any user-visible
consequences, but it's at least a bug waiting to happen.

In addition, do some code and docs review for DROP INDEX CONCURRENTLY;
some cosmetic code cleanup but mostly addition and revision of comments.

This will need to be back-patched, but in a noticeably different form,
so I'm committing it to HEAD before working on the back-patch.

Problem reported by Amit Kapila, diagnosis by Pavan Deolassee,
fix by Tom Lane and Andres Freund.
Suppress parallel build in interfaces/ecpg/preproc/.

This is to see if it will stop intermittent build failures on buildfarm
member okapi.  We know that gmake 3.82 has some problems with sometimes
not honoring dependencies in parallel builds, and it seems likely that
this is more of the same.  Since the vast bulk of the work in the preproc
directory is associated with creating preproc.c and then preproc.o,
parallelism buys us hardly anything here anyway.

Also, make both this .NOTPARALLEL and the one previously added in
interfaces/ecpg/Makefile be conditional on "ifeq ($(MAKE_VERSION),3.82)".
The known bug in gmake is fixed upstream and should not be present in
3.83 and up, and there's no reason to think it affects older releases.
When processing nested structure pointer variables ecpg always expected an
array datatype which of course is wrong.

Applied patch by Muhammad Usama <m.usama@gmail.com> to fix this.
Basic binary heap implementation.

There are probably other places where this can be used, but for now,
this just makes MergeAppend use it, so that this code will have test
coverage.  There is other work in the queue that will use this, as
well.

Abhijit Menon-Sen, reviewed by Andres Freund, Robert Haas, Álvaro
Herrera, Tom Lane, and others.
Cleanup VirtualXact at end of Hot Standby.
Correctly init fast path fields on PGPROC