On Wed, Oct 10, 2012 at 7:33 PM, Jeff Janes <jeff.janes@gmail.com> wrote:
>> Well, the real question is whether, while traversing the index, if some
>> of the pages are going to be removed from the cache by other process
>> cache usage. effective_cache_size is not figuring the cache will remain
>> between queries.
>
> Does anyone see effective_cache_size make a difference anyway? If so,
> in what circumstances?
In my case, if I set it too high, I get impossibly suboptimal plans
when an index scan over millions of rows hits the disk way too often
way too randomly. The difference is minutes for a seqscan vs hours for
the index scan. In fact, I prefer setting it too low than too high.