PG Doc comments form <nore...@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
