Only warn when connecting to a newer server, since connecting to older
servers works pretty well nowadays.  Also update the documentation a
little about current psql/server compatibility expectations.

This was removed in commit cd004067,
we're not quite sure why, but there have been reports of crashes due
to AS Perl being built with it when we are not, and it certainly
seems like the right thing to do. There is still some uncertainty
as to why it sometimes fails and sometimes doesn't.

Original patch from Owais Khani, substantially reworked and
extended by Andrew Dunstan.

The LATERAL implementation is now basically complete, and I still don't
see a cost-effective way to make an exact qual scope cross-check in the
presence of LATERAL.  However, I did add a PlannerInfo.hasLateralRTEs flag
along the way, so it's easy to make the check only when not hasLateralRTEs.
That seems to still be useful, and it beats having no check at all.

I had thought this case worked already, but perhaps I didn't re-test it
after adding extract_lateral_references() ...

checking an old running server.

We previously supposed that any given platform would supply both or neither
of these functions, so that one configure test would be sufficient.  It now
appears that at least on AIX this is not the case ... which is likely an
AIX bug, but nonetheless we need to cope with it.  So use separate tests.
Per bug #6758; thanks to Andrew Hastie for doing the followup testing
needed to confirm what was happening.

Backpatch to 9.1, where we began using these functions.

This is mostly cosmetic, but it does eliminate a speculative portability
issue.  The previous coding ignored the fact that sum_grow could easily
overflow (in fact, it could be summing multiple IEEE float infinities).
On a platform where that didn't guarantee to produce a positive result,
the code would misbehave.  In any case, it was less than readable.

Peter Eisentraut

Josh Kupershmidt

session, now that pg_terminate_backend() uses it.

Josh Kupershmidt

--enable-shared is about Plyton's configure, not ours.

queries on parent tables, per suggestion from Josh Berkus.

This reduces unnecessary exposure of other headers through htup.h, which
is very widely included by many files.

I have chosen to move the function prototypes to the new file as well,
because that means htup.h no longer needs to include tupdesc.h.  In
itself this doesn't have much effect in indirect inclusion of tupdesc.h
throughout the tree, because it's also required by execnodes.h; but it's
something to explore in the future, and it seemed best to do the htup.h
change now while I'm busy with it.

port.  The last use was QNX, per Peter Eisentraut.

Jeff Janes

autovacuum activity.

Per report from Marc Mamin

Given a query such as

SELECT * FROM foo JOIN LATERAL (SELECT foo.var1) ss(x) ON ss.x = foo.var2

the existence of the join clause "ss.x = foo.var2" encourages indxpath.c to
build a parameterized path for foo using any index available for foo.var2.
This is completely useless activity, though, since foo has got to be on the
outside not the inside of any nestloop join with ss.  It's reasonably
inexpensive to add tests that prevent creation of such paths, so let's do
that.

The existing documentation in Linux Memory Overcommit seemed to
assume that PostgreSQL itself could never be the problem, or at
least it didn't tell you what to do about it.

Per discussion with Craig Ringer and Kevin Grittner.

Report and analysis by Matthias.

Per note from Peter Eisentraut.

As suggested by Etsuro Fujita, but with somewhat different wording.

Every time the best-tuple-found-so-far changes, we need to reset all
the penalty values in which_grow[] to the penalties for the new best
tuple.  The old code failed to do this, resulting in inferior index
quality.

The original patch from Alexander Korotkov was just two lines; I took
the liberty of fleshing that out by adding a bunch of comments that I
hope will make this logic easier for others to understand than it was
for me.

push_child_plan/pop_child_plan didn't bother to adjust the "ancestors"
list of parent plan nodes when descending to a child plan node.  I think
this was okay when it was written, but it's not okay in the presence of
LATERAL references, since a subplan node could easily be returning a
LATERAL value back up to the same nestloop node that provides the value.
Per changed regression test results, the omission led to failure to
interpret Param nodes that have perfectly good interpretations.

Jeff Davis, somewhat edited by me

Python can be built to have two separate include directories: one for
platform-independent files and one for platform-specific files.  So
far, this has apparently never mattered for a PL/Python build.  But
with the new multi-arch Python packages in Debian and Ubuntu, this is
becoming the standard configuration on these platforms, so we must
check these directories separately to be able to build there.

Also add a bit of reporting in configure to be able to see better what
is going on with this.

In the initial cut at LATERAL, I kept the rule that cheapest_total_path
was always unparameterized, which meant it had to be NULL if the relation
has no unparameterized paths.  It turns out to work much more nicely if
we always have *some* path nominated as cheapest-total for each relation.
In particular, let's still say it's the cheapest unparameterized path if
there is one; if not, take the cheapest-total-cost path among those of
the minimum available parameterization.  (The first rule is actually
a special case of the second.)

This allows reversion of some temporary lobotomizations I'd put in place.
In particular, the planner can now consider hash and merge joins for
joins below a parameter-supplying nestloop, even if there aren't any
unparameterized paths available.  This should bring planning of
LATERAL-containing queries to the same level as queries not using that
feature.

Along the way, simplify management of parameterized paths in add_path()
and friends.  In the original coding for parameterized paths in 9.2,
I tried to minimize the logic changes in add_path(), so it just treated
parameterization as yet another dimension of comparison for paths.
We later made it ignore pathkeys (sort ordering) of parameterized paths,
on the grounds that ordering isn't a useful property for the path on the
inside of a nestloop, so we might as well get rid of useless parameterized
paths as quickly as possible.  But we didn't take that reasoning as far as
we should have.  Startup cost isn't a useful property inside a nestloop
either, so add_path() ought to discount startup cost of parameterized paths
as well.  Having done that, the secondary sorting I'd implemented (in
add_parameterized_path) is no longer needed --- any parameterized path that
survives add_path() at all is worth considering at higher levels.  So this
should be a bit faster as well as simpler.

reporting in contains invalid data.

This includes two micro-optimizations to the tight inner loop in descending
the SP-GiST tree: 1. avoid an extra function call to index_getprocinfo when
calling user-defined choose function, and 2. avoid a useless palloc+pfree
when node labels are not used.

Evidently I failed to test a compile after my earlier header shuffling.

The heapam XLog functions are used by other modules, not all of which
are interested in the rest of the heapam API.  With this, we let them
get just the XLog stuff in which they are interested and not pollute
them with unrelated includes.

Also, since heapam.h no longer requires xlog.h, many files that do
include heapam.h no longer get xlog.h automatically, including a few
headers.  This is useful because heapam.h is getting pulled in by
execnodes.h, which is in turn included by a lot of files.

Instead, place a forward struct declaration for struct catclist in
syscache.h.  This reduces header proliferation somewhat.

This lets files that are mere users of ResourceOwner not automatically
include the headers for stuff that is managed by the resowner mechanism.

Per Peter Geoghegan.