Re: varchar index joins not working?

Adam Gundy wrote:
> I doubt we could get stats stable enough for this. the number of groups
> will hopefully be much larger at some point.

The pg_stats table should be recording the n most-common values, so if
you have 1 million groups you track details of the 1000 most-common.
That gives you a maximum for how common any value not in the stats can be.

>> No, but let's see what's in pg_stats.
>
> no real help there. either it hits the group being read, and does a good
> plan, or it doesn't, and tries to seqscan (unless I disable it). even
> forcing stats to 1000 only bandaids the situation, given the number of
> groups will eventually exceed that..

Like I say, that's not the point of gathering the stats. If one group
represents 95% of your rows, then its group-id should be almost certain
to occur in the stats. Are you saying that's not happening with your data?

--
Richard Huxton
Archonet Ltd