2009/2/15 Michal Politowski <mpol+pg@xxxxxxx>: > I'm using PostgreSQL 8.3. > Is it normal that plans using a scan on a partial unique index > estimate that much more than one row is returned? > > Eg. I see: > -> Bitmap Index Scan on tmp_idx_oss_archive_object_id_current (cost=0.00..3.12 rows=4189 width=0) > where the tmp_idx_oss_archive_object_id_current index is a partial unique index. > > The estimated row count would be correct for the whole table but obviously not for > the part covered by the unique index. > > This happens to be a problem in this case because then the planner > prefers a sequence scan on a table joined to this one and a hash join to an index scan > and a nested loop join. Which takes hundreds of milliseconds instead of > one, so setting enable_hashjoin to false increases performance immensely. Have you run analyze since creating the unique partial index? -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
