Re: How to force PostgreSQL using an index

"Daniel Caune" <daniel.caune@ubisoft.com> writes:
> SELECT <some-columns>
>   FROM GSLOG_EVENT
>   WHERE EVENT_NAME = 'player-status-update'
>     AND EVENT_DATE_CREATED >= <start-time>
>     AND EVENT_DATE_CREATED < <end-time>

> I have an index on EVENT_DATE_CREATED that does it job.  But I though
> that I can help my favourite PostgreSQL if I create a composite index on
> EVENT_DATE_CREATED and EVENT_NAME (in that order as EVENT_DATE_CREATED
> is more dense that EVENT_NAME).

Wrong ... should be EVENT_NAME first.  Think about the sort order of the
data to see why --- your query represents a contiguous subset of the
index if EVENT_NAME is first, but not if EVENT_DATE_CREATED is first.
        regards, tom lane