Re: One of the example queries that 'could' is identical to one that 'could not'.

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От Tom Lane
Тема Re: One of the example queries that 'could' is identical to one that 'could not'.
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Msg-id 1881495.1639930503@sss.pgh.pa.us
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Ответ на One of the example queries that 'could' is identical to one that 'could not'.  (PG Doc comments form <noreply@postgresql.org>)
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PG Doc comments form <noreply@postgresql.org> writes:
> 11.9.2 lists ```SELECT x FROM tab WHERE x = 'key' AND z < 42;``` as both
> examples of 'could' and 'could not' use index-only scans.

No, look again: one of the queries uses the indexed column y,
and the other uses the non-indexed column z.

            regards, tom lane

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