Michael Brusser <michael@synchronicity.com> writes:
> Using "DEFAULT_STATISTICS_TARGET = 100" made db use index for
> field = 'abc', but field = 'xyz' still results in the table scan.
What's the actual distribution of values in these columns? Are you
searching for values that are particularly common or uncommon?
> Also 'rows' number reported in the plan is way off.
That would seem to be the crux of the problem, but you'd better be more
specific than "way off".
regards, tom lane