In checkpointer and walwriter, avoid calling PostmasterIsAlive unless
WaitLatch has reported WL_POSTMASTER_DEATH.  This saves a kernel call per
iteration of the process's outer loop, which is not all that much, but a
cycle shaved is a cycle earned.  I had already removed the unconditional
PostmasterIsAlive calls in bgwriter and pgstat in previous patches, but
forgot that WL_POSTMASTER_DEATH is supposed to be treated as untrustworthy
(per comment in unix_latch.c); so adjust those two cases to match.

There are a few other places where the same idea might be applied, but only
after substantial code rearrangement, so I didn't bother.

Get rid of some more naming choices that only make sense if you know that
this code used to be in the bgwriter, as well as some stray comments
referencing the bgwriter.

Commit 6d90eaaa added a hibernation mode
to the bgwriter to reduce the server's idle-power consumption.  However,
its interaction with the detailed behavior of BgBufferSync's feedback
control loop wasn't very well thought out.  That control loop depends
primarily on the rate of buffer allocation, not the rate of buffer
dirtying, so the hibernation mode has to be designed to operate only when
no new buffer allocations are happening.  Also, the check for whether the
system is effectively idle was not quite right and would fail to detect
a constant low level of activity, thus allowing the bgwriter to go into
hibernation mode in a way that would let the cycle time vary quite a bit,
possibly further confusing the feedback loop.  To fix, move the wakeup
support from MarkBufferDirty and SetBufferCommitInfoNeedsSave into
StrategyGetBuffer, and prevent the bgwriter from entering hibernation mode
unless no buffer allocations have happened recently.

In addition, fix the delaying logic to remove the problem of possibly not
responding to signals promptly, which was basically caused by trying to use
the process latch's is_set flag for multiple purposes.  I can't prove it
but I'm suspicious that that hack was responsible for the intermittent
"postmaster does not shut down" failures we've been seeing in the buildfarm
lately.  In any case it did nothing to improve the readability or
robustness of the code.

In passing, express the hibernation sleep time as a multiplier on
BgWriterDelay, not a constant.  I'm not sure whether there's any value in
exposing the longer sleep time as an independently configurable setting,
but we can at least make it act like this for little extra code.

Every time since the current rule for postgres.bki was put in place
when we change the major version, people complain that their tests
fail in strange ways.  This is because the version number in
postgres.bki is not updated, because it has no dependency for that.
And you can't even force the rebuild manually if you don't happen to
know which file has the problem.  Fix that now before it will happen
again.

The only remaining problem with switching major versions, as far as
the regression tests are concerned, is that contrib needs to be
rebuilt.  But that's easily invoked, and in any case the failure modes
are more friendly if you forget that.

Create separate appendixes for contrib extensions and other server
plugins on the one hand, and utility programs on the other.  Recast
the documentation of the latter as refentries, so that man pages are
generated.

Users of asynchronous-commit mode expect there to be a guaranteed maximum
delay before an async commit's WAL records get flushed to disk.  The
original version of the walwriter hibernation patch broke that.  Add an
extra shared-memory flag to allow async commits to kick the walwriter out
of hibernation mode, without adding any noticeable overhead in cases where
no action is needed.

Latch-ify the stats collector, so that it does not need an arbitrary wakeup
cycle to check for postmaster death.  The incremental savings in idle power
is pretty marginal, since we only had it waking every two seconds; but I
believe that this patch may also improve the collector's performance under
load, by reducing the number of kernel calls made per message when messages
are arriving constantly (we now avoid a select/poll call except when we
need to sleep).  The change also reduces the time needed for a normal
database shutdown on platforms where signals don't interrupt select().

This patch modifies the walwriter process so that, when it has not found
anything useful to do for many consecutive wakeup cycles, it extends its
sleep time to reduce the server's idle power consumption.  It reverts to
normal as soon as it's done any successful flushes.  It's still true that
during any async commit, backends check for completed, unflushed pages of
WAL and signal the walwriter if there are any; so that in practice the
walwriter can get awakened and returned to normal operation sooner than the
sleep time might suggest.

Also, improve the checkpointer so that it uses a latch and a computed delay
time to not wake up at all except when it has something to do, replacing a
previous hardcoded 0.5 sec wakeup cycle.  This also is primarily useful for
reducing the server's power consumption when idle.

In passing, get rid of the dedicated latch for signaling the walwriter in
favor of using its procLatch, since that comports better with possible
generic signal handlers using that latch.  Also, fix a pre-existing bug
with failure to save/restore errno in walwriter's signal handlers.

Peter Geoghegan, somewhat simplified by Tom

Placeholders such as OPTION are typically kept in singular.

This adds the variable COMP_KEYWORD_CASE, which controls in what case
keywords are completed.  This is partially to let users configure the
change from commit 69f4f1c3, but it
also offers more behaviors than were available before.

Because they use their own compilation rule, they don't use the
dependency tracking logic from Makefile.global.  To make sure that
dependency tracking works anyway for the *_srv.o files, depend on
their *.o siblings as well, which do have proper dependencies.  It's a
hack that might fail someday if there is a *_srv.o without a
corresponding *.o, but it works for now (and those would probably go
into src/backend/port/ anyway).

Josh Kupershmidt

These should not be needed anymore, at least after the recent port
removals.  So let's see whether we can do without them.

According to the Autoconf documentation, there should be a make rule

pg_config.h: stamp-h

so that with the right setup around this, a change in pg_config.h.in
will trigger a rebuild of everything that depends on pg_config.h.  But
this doesn't always work, sometimes you need to run make twice to get
everything up to date after a change of pg_config.h.in.

The fix is to write the rule as

pg_config.h: stamp-h ;

instead (with an empty command instead of no command).  This is what
Automake-generated makefiles effectively do, so it seems safe to be on
this side.

It's not actually clear why this is (apparently) more correct.  It's
been posted to
<http://lists.gnu.org/archive/html/help-make/2012-04/msg00058.html>
without response so far.

"Unexpected EOF on client connection" without an open transaction
is mostly noise, so turn it into DEBUG1. With an open transaction it's
still indicating a problem, so keep those as ERROR, and change the message
to indicate that it happened in a transaction.

version-specific files, not the server version.

Commit 62c7bd31 had assorted problems, most
visibly that it broke PREPARE TRANSACTION in the presence of session-level
advisory locks (which should be ignored by PREPARE), as per a recent
complaint from Stephen Rees.  More abstractly, the patch made the
LockMethodData.transactional flag not merely useless but outright
dangerous, because in point of fact that flag no longer tells you anything
at all about whether a lock is held transactionally.  This fix therefore
removes that flag altogether.  We now rely entirely on the convention
already in use in lock.c that transactional lock holds must be owned by
some ResourceOwner, while session holds are never so owned.  Setting the
locallock struct's owner link to NULL thus denotes a session hold, and
there is no redundant marker for that.

PREPARE TRANSACTION now works again when there are session-level advisory
locks, and it is also able to transfer transactional advisory locks to the
prepared transaction, but for implementation reasons it throws an error if
we hold both types of lock on a single lockable object.  Perhaps it will be
worth improving that someday.

Assorted other minor cleanup and documentation editing, as well.

Back-patch to 9.1, except that in the 9.1 branch I did not remove the
LockMethodData.transactional flag for fear of causing an ABI break for
any external code that might be examining those structs.

The default for the choice attribute of the <arg> element is "opt",
which would normally put the argument inside brackets.  But the DSSSL
stylesheets contain a hack that treats <arg> directly inside <group>
specially, so that <group><arg>-x</arg><arg>-y</arg></group> comes out
as [ -x | -y ] rather than [ [-x] | [-y] ], which it would technically
be.  But when building man pages, this doesn't work, and so the
command synopses on the man pages contain lots of extra brackets.

By putting choice="opt" or choice="plain" explicitly on every <arg>
and <group> element, we avoid any toolchain dependencies like that,
and it also makes it clearer in the source code what is meant.

In passing, make some small corrections in the documentation about
which arguments are really optional or not.

Postgres 9.2, and perhaps no existing users either.

Add test cases for inline handler of plython2u (when using that
language name), and for result object element assignment.  There is
now at least one test case for every top-level functionality, except
plpy.Fatal (annoying to use in regression tests) and result object
slice retrieval and slice assignment (which are somewhat broken).

Allocate PLyResultObject.tupdesc in TopMemoryContext, because its
lifetime is the lifetime of the Python object and it shouldn't be
freed by some other memory context, such as one controlled by SPI.  We
trust that the Python object will clean up its own memory.

Before, this would crash the included regression test case by trying
to use memory that was already freed.

reported by Asif Naeem, analysis by Tom Lane

At the time we check whether the tuple is dead to all running
transactions, we've already verified that it isn't visible to our
scan, setting hint bits if appropriate.  So there's no need to
recheck CLOG for the all-dead test we do just a moment later.
So, add HeapTupleIsSurelyDead() to test the appropriate condition
under the assumption that all relevant hit bits are already set.

Review by Tom Lane.

Thom Brown

Found these with grep -r "for for ".

Both terms still appear in a few places, but I thought it best to leave
those alone in context.