Re: Performance-improvement idea: shortcircuit unique-index checks

Bruce Momjian <pgman@candle.pha.pa.us> writes:
> Seems a better solution would be to put a 'deleted' bit in the index so
> we would have to visit those heap tuples only once for a committed
> status.  Similar to what we do with heap tuples so we don't have to
> visit pg_log repeatedly.

That's only a partial solution, since the index is still going to have
to visit the row's existing tuple (which is, by definition, not yet
committed dead).  My point is that the index scanning done for
uniqueness checks can be eliminated *entirely* for one pretty-common
case.

A deleted bit in index entries might be useful too, but I think it
attacks a different set of cases.
        regards, tom lane