Re: Seqscan rather than Index

Greg Stark <gsstark(at)mit(dot)edu> writes:
> Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
>> I think the one effect that's not being modeled is amortization of index
>> fetches across successive queries.

> And across multiple fetches in a single query, such as with a nested loop.

Right, that's effectively the same problem. You could imagine making a
special-purpose solution for nestloop queries but I think the issue is
more general than that.

> It seems like the effective_cache_size parameter should be having some
> influence here.

But it doesn't :-(. e_c_s is currently only used to estimate
amortization of repeated heap-page fetches within a single indexscan.

regards, tom lane