=?koi8-r?B?/cXLyc4g8dLP08zB1w==?= <ladayaroslav@xxxxxxxxx> writes: > I've noticed strange row count estimations in BETWEEN predicate: > EXPLAIN > SELECT * > FROM t1 > WHERE f1 = 42; > -->> Bitmap Heap Scan on t1 (cost=203.07..28792.94 rows=10662 width=24) <skipped> > EXPLAIN > SELECT * > FROM t1 > WHERE f1 BETWEEN 42 AND 42; > -->> Index Scan using table1_field1_idx on t1 (cost=0.44..8.46 rows=1 width=24) <skipped> > Why row count estimations for two logically equivalent queries are so > different? PG doesn't try to estimate inequalities exactly, because it usually doesn't make enough of a difference to matter. Currently we don't even bother to distinguish say ">" from ">=" for estimation purposes, though certainly we would need to in order to deal with zero-width ranges with any great amount of precision. regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
