Alvaro Herrera <alvherre@commandprompt.com> writes:
> Hmm, I'm placing bets on the bpchar weirdness. I'd try getting rid of
> that and using plain varchar for all the columns.
That's certainly what's inhibiting it from considering an indexscan
on the larger table. I'm not as convinced as the OP that a nestloop
indexscan is really going to win compared to the hash plan, but if
the comparison value is varchar then an index on a bpchar column
is simply not useful --- at least not unless you stick an explicit
cast into the query, so that the comparison will have bpchar rather
than varchar semantics.
regards, tom lane