Fix possible cache invalidation failure in ReceiveSharedInvalidMessages.

Commit fad153ec45299bd4d4f29dec8d9e04e2f1c08148 modified sinval.c to reduce
the number of calls into sinvaladt.c (which require taking a shared lock)
by keeping a local buffer of collected-but-not-yet-processed messages.
However, if processing of the last message in a batch resulted in a
recursive call to ReceiveSharedInvalidMessages, we could overwrite that
message with a new one while the outer invalidation function was still
working on it.  This would be likely to lead to invalidation of the wrong
cache entry, allowing subsequent processing to use stale cache data.
The fix is just to make a local copy of each message while we're processing
it.

Spotted by Andres Freund.  Back-patch to 8.4 where the bug was introduced.
Remove tabs after spaces in C comments

This was not changed in HEAD, but will be done later as part of a
pgindent run.  Future pgindent runs will also do this.

Report by Tom Lane

Backpatch through all supported branches, but not HEAD
Fix interval test, which was broken for floating-point timestamps.

Commit 4318daecc959886d001a6e79c6ea853e8b1dfb4b introduced a test that
couldn't be made consistent between integer and floating-point
timestamps.

It was designed to test the longest possible interval output length,
so removing four zeros from the number of hours, as this patch does,
is not ideal. But the test still has some utility for its original
purpose, and there aren't a lot of other good options.

Noah Misch suggested a different approach where we test that the
output either matches what we expect from integer timestamps or what
we expect from floating-point timestamps. That seemed to obscure an
otherwise simple test, however.

Reviewed by Tom Lane and Noah Misch.
Fix failure to set ActiveSnapshot while rewinding a cursor.

ActiveSnapshot needs to be set when we call ExecutorRewind because some
plan node types may execute user-defined functions during their ReScan
calls (nodeLimit.c does so, at least).  The wisdom of that is somewhat
debatable, perhaps, but for now the simplest fix is to make sure the
required context is valid.  Failure to do this typically led to a
null-pointer-dereference core dump, though it's possible that in more
complex cases a function could be executed with the wrong snapshot
leading to very subtle misbehavior.

Per report from Leif Jensen.  It's been broken for a long time, so
back-patch to all active branches.
Avoid buffer bloat in libpq when server is consistently faster than client.

If the server sends a long stream of data, and the server + network are
consistently fast enough to force the recv() loop in pqReadData() to
iterate until libpq's input buffer is full, then upon processing the last
incomplete message in each bufferload we'd usually double the buffer size,
due to supposing that we didn't have enough room in the buffer to finish
collecting that message.  After filling the newly-enlarged buffer, the
cycle repeats, eventually resulting in an out-of-memory situation (which
would be reported misleadingly as "lost synchronization with server").
Of course, we should not enlarge the buffer unless we still need room
after discarding already-processed messages.

This bug dates back quite a long time: pqParseInput3 has had the behavior
since perhaps 2003, getCopyDataMessage at least since commit 70066eb1a1ad
in 2008.  Probably the reason it's not been isolated before is that in
common environments the recv() loop would always be faster than the server
(if on the same machine) or faster than the network (if not); or at least
it wouldn't be slower consistently enough to let the buffer ramp up to a
problematic size.  The reported cases involve Windows, which perhaps has
different timing behavior than other platforms.

Per bug #7914 from Shin-ichi Morita, though this is different from his
proposed solution.  Back-patch to all supported branches.
Protect against torn pages when deleting GIN list pages.

To-be-deleted list pages contain no useful information, as they are being
deleted, but we must still protect the writes from being torn by a crash
after a partial write. To do that, re-initialize the pages on WAL replay.

Jeff Janes caught this with a test program to test partial writes.
Backpatch to all supported versions.
Un-break ecpg test suite under --disable-integer-datetimes.

Commit 4318daecc959886d001a6e79c6ea853e8b1dfb4b broke it.  The change in
sub-second precision at extreme dates is normal.  The inconsistent
truncation vs. rounding is essentially a bug, albeit a longstanding one.
Back-patch to 8.4, like the causative commit.
Document permissions needed for pg_database_size and pg_tablespace_size.

Back in 8.3, we installed permissions checks in these functions (see
commits 8bc225e7990a and cc26599b7206).  But we forgot to document that
anywhere in the user-facing docs; it did get mentioned in the 8.3 release
notes, but nobody's looking at that any more.  Per gripe from Suya Huang.
Accept tcl 8.6 in configure's probe for tclsh.

Usually the search would find plain "tclsh" without any trouble,
but some installations might only have the version-numbered flavor
of that program.

No compatibility problems have been reported with 8.6, so we might
as well back-patch this to all active branches.

Christoph Berg
Initialize padding bytes in btree_gist varbit support.

The code expands a varbit gist leaf key to a node key by copying the bit
data twice in a varlen datum, as both the lower and upper key. The lower key
was expanded to INTALIGN size, but the padding bytes were not initialized.
That's a problem because when the lower/upper keys are compared, the padding
bytes are used compared too, when the values are otherwise equal. That could
lead to incorrect query results.

REINDEX is advised for any btree_gist indexes on bit or bit varying data
type, to fix any garbage padding bytes on disk.

Per Valgrind, reported by Andres Freund. Backpatch to all supported
versions.
In initdb, ensure stdout/stderr buffering behavior is what we expect.

Since this program may print to either stdout or stderr, the relative
ordering of its messages depends on the buffering behavior of those files.
Force stdout to be line-buffered and stderr to be unbuffered, ensuring
that the behavior will match standard Unix interactive behavior, even
when stdout and stderr are rerouted to a file.

Per complaint from Tomas Vondra.  The particular case he pointed out is
new in HEAD, but issues of the same sort could arise in any branch with
other error messages, so back-patch to all branches.

I'm unsure whether we might not want to do this in other client programs
as well.  For the moment, just fix initdb.
Fix race condition in preparing a transaction for two-phase commit.

To lock a prepared transaction's shared memory entry, we used to mark it
with the XID of the backend. When the XID was no longer active according
to the proc array, the entry was implicitly considered as not locked
anymore. However, when preparing a transaction, the backend's proc array
entry was cleared before transfering the locks (and some other state) to
the prepared transaction's dummy PGPROC entry, so there was a window where
another backend could finish the transaction before it was in fact fully
prepared.

To fix, rewrite the locking mechanism of global transaction entries. Instead
of an XID, just have simple locked-or-not flag in each entry (we store the
locking backend's backend id rather than a simple boolean, but that's just
for debugging purposes). The backend is responsible for explicitly unlocking
the entry, and to make sure that that happens, install a callback to unlock
it on abort or process exit.

Backpatch to all supported versions.
Handle duplicate XIDs in txid_snapshot.

The proc array can contain duplicate XIDs, when a transaction is just being
prepared for two-phase commit. To cope, remove any duplicates in
txid_current_snapshot(). Also ignore duplicates in the input functions, so
that if e.g. you have an old pg_dump file that already contains duplicates,
it will be accepted.

Report and fix by Jan Wieck. Backpatch to all supported versions.