| From: | Alvaro Herrera <alvherre(at)dcc(dot)uchile(dot)cl> |
|---|---|
| To: | "Jim C(dot) Nasby" <decibel(at)decibel(dot)org> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Wes <wespvp(at)syntegra(dot)com>, Postgresql-General <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: How are foreign key constraints built? |
| Date: | 2005-01-23 21:45:36 |
| Message-ID: | 20050123214536.GG19315@dcc.uchile.cl |
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| Thread: | |
| Lists: | pgsql-general |
On Sun, Jan 23, 2005 at 03:19:10PM -0600, Jim C. Nasby wrote:
> > People have this weird notion that an index-based plan is always faster
> > than anything else. If you like you can try the operation with "set
> > enable_seqscan = off", but I bet it will take longer.
>
> Well, every other database I've used can do index covering, which means
> index scans *are* faster.
... on those database systems. Indexes are different in Postgres in
general: they don't have visibility info (other systems don't need it,
tuples are always visible), and in some databases you have clustered
indexes, where the index is also the heap.
--
Alvaro Herrera (<alvherre[(at)]dcc(dot)uchile(dot)cl>)
"We are who we choose to be", sang the goldfinch
when the sun is high (Sandman)
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