Re: Way to avoid expensive Recheck Cond in index lookup? - Mailing list pgsql-general

"Matt Magoffin" <postgresql.org@msqr.us> writes:
> The problem for me is, the Recheck Cond is then on the xpath() function
> used by the function-based index. My understanding is that then the
> database must actually call the xpath() function again on all matches from
> the index lookup.

This is mistaken.  It only happens if there are so many hits that the
bitmap becomes lossy (which you can control to some extent anyway by
adjusting work_mem).

            regards, tom lane