Claudio Freire <[email protected]> writes:
> On Mon, Oct 31, 2011 at 2:08 PM, Robert Haas <[email protected]> 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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