> > IMHO this is somewhat non-optimal. In the absence of information
> > to the contrary, PostgreSQL should default to using an index if
> > it might be appropriate, not ignore it.
>
> This is an interesting idea. So you are saying that if a
> column has no
> vacuum analyze statistics, assume it is unique? Or are you talking
> about a table that has never been vacuumed? Then we assume it is a
> large table. Interesting. It would help some queries, but
> hurt others.
It would help where it counts, since if the table is small it won't matter
that much
wheather we use the index or not. For small tables we are talking about
subsecond
differences, whereas for large tables we are talking about minutes or hours.
> We have gone around and around on what the default stats should be.
> Tom Lane can comment on this better than I can.
I think Tom has done a good job, it is this special query that seems to
fail.
Andreas
