In particular, make hstore @> '' succeed for all hstores, likewise
hstore ?& '{}'.  Previously the results were inconsistent and could
depend on whether you were using a GiST index, GIN index, or seqscan.

Move the actual functionality into a separate function that's
easier to call internally, and change the SQL-callable function
to be a wrapper calling this.

Also create a pg_abort_backup() function, only callable internally,
that does only the most vital parts of pg_stop_backup(), making it
safe(r) to call from error handlers.

This bug was exercised by contrib/intarray/bench, as noted by Tom Lane.

No need for the empty-prefix-match kluge to force a full scan anymore.

This applies the fix for bug #5784 to remaining places where we wish
to reject nulls in user-supplied arrays.  In all these places, there's
no reason not to allow a null bitmap to be present, so long as none of
the current elements are actually null.

I did not change some other places where we are looking at system catalog
entries or aggregate transition values, as the presence of a null bitmap
in such an array would be suspicious.

Result of bad testing of my last commit.

This file is now needed by pgAdmin builds, which started
failing since it was missing in the installer builds.

Add support for reading back information about the symbolic
links we've created with pgsymlink(), which are actually
Junction Points. Just like pgsymlink() can only create directory
symlinks, pgreadlink() can only read directory symlinks.

The array containment operators now behave per mathematical expectation
for empty arrays (ie, an empty array is contained in anything).
Both these operators and the query_int operators now work as expected in
GiST and GIN index searches, rather than having corner cases where the
index searches gave different answers.

Also, fix unexpected failures where the operators would claim that an array
contained nulls, when in fact there was no longer any null present (similar
to bug #5784).  The restriction to not have nulls is still there, as
removing it would take a lot of added code complexity and probably slow
things down significantly.

Also, remove the arbitrary restriction to 1-D arrays; unlike the other
restriction, this was buying us nothing performance-wise.

Assorted cosmetic improvements and marginal performance improvements, too.

This will support fixing contrib/intarray (and probably other places)
so that they don't have to fail on arrays that contain a null bitmap
but no live null entries.

The only reason this wasn't crashing while testing the core anyarray
operators was that it was disabled for those cases because of passing the
wrong type information to get_opfamily_proc :-(.  So fix that too, and make
it insist on finding the support proc --- in hindsight, silently doing
nothing is not as sane a coping mechanism as all that.

The only use we have had for amindexnulls is in determining whether an
index is safe to cluster on; but since the addition of the amclusterable
flag, that usage is pretty redundant.

In passing, clean up assorted sloppiness from the last patch that touched
pg_am.h: Natts_pg_am was wrong, and ambuildempty was not documented.

The original coding could combine duplicate entries only when they
originated from the same qual condition.  In particular it could not
combine cases where multiple qual conditions all give rise to full-index
scan requests, which is an expensive case well worth optimizing.  Refactor
so that duplicates are recognized across all the quals.

up relations, but rather order old/new relations and use the same array
index value for both.  This should speed up pg_upgrade for databases
with many relations.

that we restore by oid;  they can be handled like regular tables when
creating the file mapping structure.

Josh Kupershmidt

The underlying C code still needs work, but this at least gets its
current regression test passing again.

in pg_largeobject_metadata).

because the old and new values are identical.

which is stored in pg_largeobject_metadata.

No backpatch to 9.0 because you can't migrate from 9.0 to 9.0 with the
same catversion (because of tablespace conflict), and a pre-9.0
migration to 9.0 has not large object permissions to migrate.

Toast tables have identical pg_class.oid and pg_class.relfilenode, but
for clarity it is good to preserve the pg_class.oid.

Update comments regarding what is preserved, and do some
variable/function renaming for clarity.

Add more "internal" arguments so that these pg_proc entries reflect the
current preferred API.  This is purely a cosmetic change, since GIN doesn't
actually consult the pg_proc entry when calling a support function.
Accordingly, no catversion bump.

Per my recent proposal(s).  Null key datums can now be returned by
extractValue and extractQuery functions, and will be stored in the index.
Also, placeholder entries are made for indexable items that are NULL or
contain no keys according to extractValue.  This means that the index is
now always complete, having at least one entry for every indexed heap TID,
and so we can get rid of the prohibition on full-index scans.  A full-index
scan is implemented much the same way as partial-match scans were already:
we build a bitmap representing all the TIDs found in the index, and then
drive the results off that.

Also, introduce a concept of a "search mode" that can be requested by
extractQuery when the operator requires matching to empty items (this is
just as cheap as matching to a single key) or requires a full index scan
(which is not so cheap, but it sure beats failing or giving wrong answers).
The behavior remains backward compatible for opclasses that don't return
any null keys or request a non-default search mode.

Using these features, we can now make the GIN index opclass for anyarray
behave in a way that matches the actual anyarray operators for &&, <@, @>,
and = ... which it failed to do before in assorted corner cases.

This commit fixes the core GIN code and ginarrayprocs.c, updates the
documentation, and adds some simple regression test cases for the new
behaviors using the array operators.  The tsearch and contrib GIN opclass
support functions still need to be looked over and probably fixed.

Another thing I intend to fix separately is that this is pretty inefficient
for cases where more than one scan condition needs a full-index search:
we'll run duplicate GinScanEntrys, each one of which builds a large bitmap.
There is some existing logic to merge duplicate GinScanEntrys but it needs
refactoring to make it work for entries belonging to different scan keys.

Note that most of gin.h has been split out into a new file gin_private.h,
so that gin.h doesn't export anything that's not supposed to be used by GIN
opclasses or the rest of the backend.  I did quite a bit of other code
beautification work as well, mostly fixing comments and choosing more
appropriate names for things.

Itagaki Takahiro, edited by me.

Jehan-Guillaume de Rorthais, with some additional wordsmithing by me.

Itagaki Takahiro and Simon Riggs.

functions.

The previous example didn't make it clear whether array_upper returned
the last element or the index of the last element.

lo_insert.