Arshavir Grigorian <ag@m-cam.com> writes:
> I have a query that when run on similar tables in 2 different databases
> either uses the index on the column (primary key) in the where clause or
> does a full table scan. The structure of the tables is the same, except
> that the table where the index does not get used has an extra million
> rows (22mil vs 23mil).
I'd say you initialized the second database in a non-C locale. The
planner is clearly well aware that the seqscan is going to be expensive,
so the explanation has to be that it does not have a usable index available.
regards, tom lane