Re: Sequential scan instead of index scan

Ioannis Anagnostopoulos <ioannis(at)anatec(dot)com> writes:
> I think this is a pretty good plan and quite quick given the
> size of the table (88Million rows at present). However in real
> life the parameter where I search for msg_id is not an array of
> 3 ids but of 300.000 or more. It is then that the query forgets
> the plan and goes to sequential scan. Is there any way around?

If you've got that many, any(array[....]) is a bad choice. I'd try
putting the IDs into a VALUES(...) list, or even a temporary table, and
then writing the query as a join. It is a serious mistake to think that
a seqscan is evil when you're dealing with joining that many rows, btw.
What you should probably be looking for is a hash join plan.

regards, tom lane