Robert Haas <[email protected]> writes:
> On Tue, Jul 23, 2013 at 12:28 PM, Tom Lane <[email protected]> wrote:
>> As far as get_actual_variable_range() is concerned, an MVCC snapshot
>> would probably be the thing to use anyway;
> That surprises me, though. I really thought the point was to cost the
> index scan, and surely that will be slowed down even by entries we
> can't see.
No, the usage (or the main usage anyway) is for selectivity estimation,
ie how many rows will the query fetch.
regards, tom lane
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