On Tue, Jul 10, 2018 at 03:57:52PM +0000, PG Doc comments form wrote: > The following documentation comment has been logged on the website: > > Page: > https://www.postgresql.org/docs/10/static/multivariate-statistics-examples.html > Description: > > Hi All, > > I'm a little confused by the documentation here: > https://www.postgresql.org/docs/10/static/multivariate-statistics-examples.html. > > > In particular, the selectivity of the second query doesn't seem to match up > with what is expected in the notes. I feel like I may be missing something? > > > (I am referring to the output of this explain command: EXPLAIN (ANALYZE, > TIMING OFF) SELECT * FROM t WHERE a = 1 AND b = 1;)
Uh, the first query shows an _estimate_ of rows=1, which does not match the actual rows=100: Seq Scan on t (cost=0.00..195.00 rows=1 width=8) (actual rows=100 loops=1) The second query has it right: Seq Scan on t (cost=0.00..195.00 rows=100 width=8) (actual rows=100 loops=1) -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + As you are, so once was I. As I am, so you will be. + + Ancient Roman grave inscription +