Claudio Freire <klaussfre...@gmail.com> writes:
> On Mon, Oct 31, 2011 at 2:08 PM, Robert Haas <robertmh...@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?

Sure it does.  It doesn't usually think they're efficient enough,
because they require full-index scans.  But sometimes that's the
best you can do.

                        regards, tom lane

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