Fix whitespace
doc: Disable indentation of XHTML output

Indenting the XHTML output can lead to incorrect rendering.  This only
affects the build via XSLT.
Assert(IsTransactionState()) in RelationIdGetRelation().

Commit 42c80c696e9c8323841180029cc62741c21bd356 added an
Assert(IsTransactionState()) in SearchCatCache(), to catch
any code that thought it could do a catcache lookup outside
transactions.  Extend the same idea to relcache lookups.
Alphabeticize list in OBJS definition in utils/adt Makefile.
In RelationClearRelation, postpone cache reload if !IsTransactionState().

We may process relcache flush requests during transaction startup or
shutdown.  In general it's not terribly safe to do catalog access at those
times, so the code's habit of trying to immediately revalidate unflushable
relcache entries is risky.  Although there are no field trouble reports
that are positively traceable to this, we have been able to demonstrate
failure of the assertions recently added in RelationIdGetRelation() and
SearchCatCache().  On the other hand, it seems safe to just postpone
revalidation of the cache entry until we're inside a valid transaction.
The one case where this is questionable is where we're exiting a
subtransaction and the outer transaction is holding the relcache entry open
--- but if we made any significant changes to the rel inside such a
subtransaction, we've got problems anyway.  There are mechanisms in place
to prevent that (to wit, locks for cross-session cases and
CheckTableNotInUse() for intra-session cases), so let's trust to those
mechanisms to keep us out of trouble.
Fix thinko in comment.

Amit Langote
Speed up "rare & frequent" type GIN queries.

If you have a GIN query like "rare & frequent", we currently fetch all the
items that match either rare or frequent, call the consistent function for
each item, and let the consistent function filter out items that only match
one of the terms. However, if we can deduce that "rare" must be present for
the overall qual to be true, we can scan all the rare items, and for each
rare item, skip over to the next frequent item with the same or greater TID.
That greatly speeds up "rare & frequent" type queries.

To implement that, introduce the concept of a tri-state consistent function,
where the 3rd value is MAYBE, indicating that we don't know if that term is
present. Operator classes only provide a boolean consistent function, so we
simulate the tri-state consistent function by calling the boolean function
several times, with the MAYBE arguments set to all combinations of TRUE and
FALSE. Testing all combinations is only feasible for a small number of MAYBE
arguments, but it is envisioned that we'll provide a way for operator
classes to provide a native tri-state consistent function, which can be much
more efficient. But that is not included in this patch.

We were already using that trick to for lossy pages, calling the consistent
function with the lossy entry set to TRUE and FALSE. Now that we have the
tri-state consistent function, use it for lossy pages too.

Alexander Korotkov, with fair amount of refactoring by me.
Initialize the entryRes array between each call to triConsistent.

The shimTriConstistentFn, which calls the opclass's consistent function with
all combinations of TRUE/FALSE for any MAYBE argument, modifies the entryRes
array passed by the caller. Change startScanKey to re-initialize it between
each call to accommodate that.

It's actually a bad habit by shimTriConsistentFn to modify its argument. But
the only caller that doesn't already re-initialize the entryRes array was
startScanKey, and it's easy for startScanKey to do so. Add a comment to
shimTriConsistentFn about that.

Note: this does not give a free pass to opclass-provided consistent
functions to modify the entryRes argument; shimTriConsistent assumes that
they don't, even though it does it itself.

While at it, refactor startScanKey to allocate the requiredEntries and
additionalEntries after it knows exactly how large they need to be. Saves a
little bit of memory, and looks nicer anyway.

Per complaint by Tom Lane, buildfarm and the pg_trgm regression test.