Misc GIN refactoring.

Merge the isEnoughSpace and placeToPage functions in the b-tree interface
into one function that tries to put a tuple on page, and returns false if
it doesn't fit.

Move createPostingTree function to gindatapage.c, and change its contract
so that it can be passed more items than fit on the root page. It's in a
better position than the callers to know how many items fit.

Move ginMergeItemPointers out of gindatapage.c, into a separate file.

These changes make no difference now, but reduce the footprint of Alexander
Korotkov's upcoming patch to pack item pointers more tightly.
Fix missing argument and function prototypes.

Not sure how I missed these in previous commit.
Keep heap open until new heap generated in RMV.

Early close became apparent when invalidation messages were
processed in a new location under CLOBBER_CACHE_ALWAYS builds, due
to additional locking.

Back-patch to 9.3
Support default arguments and named-argument notation for window functions.

These things didn't work because the planner omitted to do the necessary
preprocessing of a WindowFunc's argument list.  Add the few dozen lines
of code needed to handle that.

Although this sounds like a feature addition, it's really a bug fix because
the default-argument case was likely to crash previously, due to lack of
checking of the number of supplied arguments in the built-in window
functions.  It's not a security issue because there's no way for a
non-superuser to create a window function definition with defaults that
refers to a built-in C function, but nonetheless people might be annoyed
that it crashes rather than producing a useful error message.  So
back-patch as far as the patch applies easily, which turns out to be 9.2.
I'll put a band-aid in earlier versions as a separate patch.

(Note that these features still don't work for aggregates, and fixing that
case will be harder since we represent aggregate arg lists as target lists
not bare expression lists.  There's no crash risk though because CREATE
AGGREGATE doesn't accept defaults, and we reject named-argument notation
when parsing an aggregate call.)
Be more robust when strerror() doesn't give a useful result.

glibc, at least, is capable of returning "???" instead of anything useful
if it doesn't like the setting of LC_CTYPE.  If this happens, or in the
previously-known case of strerror() returning an empty string, try to
print the C macro name for the error code ("EACCES" etc).  Only if we
don't have the error code in our compiled-in list of popular error codes
(which covers most though not quite all of what's called out in the POSIX
spec) will we fall back to printing a numeric error code.  This should
simplify debugging.

Note that this functionality is currently only provided for %m in backend
ereport/elog messages.  That may be sufficient, since we don't fool with the
locale environment in frontend clients, but it's foreseeable that we might
want similar code in libpq for instance.

There was some talk of back-patching this, but let's see how the buildfarm
likes it first.  It seems likely that at least some of the POSIX-defined
error code symbols don't exist on all platforms.  I don't want to clutter
the entire list with #ifdefs, but we may need more than are here now.

MauMau, edited by me
Add #ifdef guards for some POSIX error symbols that Windows doesn't like.

Per buildfarm results.  It looks like the older the Windows version, the
more errno codes it hasn't got ...
Fix setting of right bound at GIN page split.

Broken by my refactoring.
Fix generation of MergeAppend plans for optimized min/max on expressions.

Before jamming a desired targetlist into a plan node, one really ought to
make sure the plan node can handle projections, and insert a buffering
Result plan node if not.  planagg.c forgot to do this, which is a hangover
from the days when it only dealt with IndexScan plan types.  MergeAppend
doesn't project though, not to mention that it gets unhappy if you remove
its possibly-resjunk sort columns.  The code accidentally failed to fail
for cases in which the min/max argument was a simple Var, because the new
targetlist would be equivalent to the original "flat" tlist anyway.
For any more complex case, it's been broken since 9.1 where we introduced
the ability to optimize min/max using MergeAppend, as reported by Raphael
Bauduin.  Fix by duplicating the logic from grouping_planner that decides
whether we need a Result node.

In 9.2 and 9.1, this requires back-porting the tlist_same_exprs() function
introduced in commit 4387cf956b9eb13aad569634e0c4df081d76e2e3, else we'd
uselessly add a Result node in cases that worked before.  It's rather
tempting to back-patch that whole commit so that we can avoid extra Result
nodes in mainline cases too; but I'll refrain, since that code hasn't
really seen all that much field testing yet.
Prevent display of dropped columns in row constraint violation messages.

ExecBuildSlotValueDescription() printed "null" for each dropped column in
a row being complained of by ExecConstraints().  This has some sanity in
terms of the underlying implementation, but is of course pretty surprising
to users.  To fix, we must pass the target relation's descriptor to
ExecBuildSlotValueDescription(), because the slot descriptor it had been
using doesn't get labeled with attisdropped markers.

Per bug #8408 from Maxim Boguk.  Back-patch to 9.2 where the feature of
printing row values in NOT NULL and CHECK constraint violation messages
was introduced.

Michael Paquier and Tom Lane
Silence benign warnings from clang version 3.0-6ubuntu3.
Make LOCK_PRINT & PROCLOCK_PRINT expand to ((void) 0) when not in use.

This avoids warnings from more-anal-than-average compilers, and might
prevent hidden syntax problems in the future.

Andres Freund
Fix subtly-wrong volatility checking in BeginCopyFrom().

contain_volatile_functions() is best applied to the output of
expression_planner(), not its input, so that insertion of function
default arguments and constant-folding have been done.  (See comments
at CheckMutability, for instance.)  It's perhaps unlikely that anyone
will notice a difference in practice, but still we should do it properly.

In passing, change variable type from Node* to Expr* to reduce the net
number of casts needed.

Noted while perusing uses of contain_volatile_functions().
Make contain_volatile_functions/contain_mutable_functions look into SubLinks.

This change prevents us from doing inappropriate subquery flattening in
cases such as dangerous functions hidden inside a sub-SELECT in the
targetlist of another sub-SELECT.  That could result in unexpected behavior
due to multiple evaluations of a volatile function, as in a recent
complaint from Etienne Dube.  It's been questionable from the very
beginning whether these functions should look into subqueries (as noted in
their comments), and this case seems to provide proof that they should.

Because the new code only descends into SubLinks, not SubPlans or
InitPlans, the change only affects the planner's behavior during
prepjointree processing and not later on --- for example, you can still get
it to use a volatile function in an indexqual if you wrap the function in
(SELECT ...).  That's a historical behavior, for sure, but it's reasonable
given that the executor's evaluation rules for subplans don't depend on
whether there are volatile functions inside them.  In any case, we need to
constrain the behavioral change as narrowly as we can to make this
reasonable to back-patch.
Add the notion of REPLICA IDENTITY for a table.

Pending patches for logical replication will use this to determine
which columns of a tuple ought to be considered as its candidate key.

Andres Freund, with minor, mostly cosmetic adjustments by me
Fix pg_isolation_regress to work outside its build directory.

This makes it possible to, for example, use the isolation tester to
test a contrib module.

Andres Freund
doc: Clarify under what circumstances pg_dump needs superuser access.

Inspired by, but different from, a patch from Ivan Lezhnjov IV
Fix race condition in GIN posting tree page deletion.

If a page is deleted, and reused for something else, just as a search is
following a rightlink to it from its left sibling, the search would continue
scanning whatever the new contents of the page are. That could lead to
incorrect query results, or even something more curious if the page is
reused for a different kind of a page.

To fix, modify the search algorithm to lock the next page before releasing
the previous one, and refrain from deleting pages from the leftmost branch
of the tree.

Add a new Concurrency section to the README, explaining why this works.
There is a lot more one could say about concurrency in GIN, but that's for
another patch.

Backpatch to all supported versions.
Fix ECPG compiler warning.

Commit 9b4d52f2095be96ca238ce41f6963ec56376491f failed to notice
that pg_regress_ecpg needed updating.

This patch was independently submitted by both David Rowley
and Andres Freund.
Fix whitespace issues found by git diff --check, add gitattributes

Set per file type attributes in .gitattributes to fine-tune whitespace
checks.  With the associated cleanups, the tree is now clean for git
Don't abort pg_basebackup when receiving empty WAL block

This is a similar fix as c6ec8793aa59d1842082e14b4b4aae7d4bd883fd
9.2. This should never happen in 9.3 and newer since the special case
cannot happen there, but this patch synchronizes up the code so there
is no confusion on why they're different. An empty block is as harmless
in 9.3 as it was in 9.2, and can safely be ignored.