"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