Re: How to force PostgreSQL using an index

> -----Message d'origine-----
> De : Tom Lane [mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us]
> Envoyé : mercredi, février 15, 2006 17:47
> À : Daniel Caune
> Cc : Andrew Sullivan; pgsql-sql(at)postgresql(dot)org
> Objet : Re: [SQL] How to force PostgreSQL using an index
>
> "Daniel Caune" <daniel(dot)caune(at)ubisoft(dot)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

Yes, you're right!