Re: BUG #6232: hstore operator ? no longer uses indexes

"Pierre Ducroquet" <p.psql@pinaraf.info> writes:
> [ the "hstore ? text" operator no longer matches an hstore GIST index ]

Hmm ... this doesn't seem to be specific to either hstore or GIST; it's
a collation problem.  The index is marked as having no collation, which
is reasonable since hstore is a collation-less type.  However, the ?
OpExpr gets marked as having "default" collation because it has one
collatable input, namely the text constant.  And then,
match_clause_to_indexcol decides the clause doesn't match the index.

Not sure what to do about this.  Is it okay to suppose that collation
can be ignored when matching to a collation-less index?  If not, what's
the correct rule?  I don't like the idea of concluding that hstore has
to be forcibly assigned a collation just because it has some operators
that accept text ...

            regards, tom lane