Re: Composite keys - Mailing list pgsql-performance

From Claudio Freire
Subject Re: Composite keys
Date
Msg-id CAGTBQpb1E7jQBn1S-yBCMo2w=V+iQRed-sDqNTj=cKPnYRicRg@mail.gmail.com
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In response to Re: Composite keys  (Robert Haas <robertmhaas@gmail.com>)
Responses Re: Composite keys  (Robert Haas <robertmhaas@gmail.com>)
Re: Composite keys  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-performance
On Mon, Oct 31, 2011 at 2:08 PM, Robert Haas <robertmhaas@gmail.com> wrote:
>> Multicolumn indices on (c1, c2, ..., cn) can only be used on where
>> clauses involving c1..ck with k<n.
>
> I don't think that's true.  I believe it can be used for a query that
> only touches, say, c2.  It's just extremely inefficient.

Does postgres generate those kinds of plans?
I do not think so. I've never seen it happening.

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