If you want something done right, I guess you have to do it yourself! Here's the answer to my question. It works great! Or so it seems to:
delete from pg_statistic s where exists ( select 1 from pg_class as c, pg_attribute as a where a.attrelid = c.relfilenode and s.starelid = c.relfilenode and s.staattnum = a.attnum and c.relname = 'maindb_astobject' and attname = 'survey_id' ); In the above SQL statement, "maindb_astobject" is the name of the table and "survey_id" is the name of the column. The statement deletes all the statistics for the specified column in the specified table. |>ouglas On Mon, Jun 1, 2009 at 2:20 PM, Douglas Alan <darkwate...@gmail.com> wrote: > I'd like to manually alter the statistics for a column, as for the column > in question the statistics are causing Postgres to do the wrong thing for my > purposes. (I.e., a Seq Scan, rather than an Index Scan.) If someone can > tell me how to achieve this, I would quite grateful. > > Thanks! > |>ouglas > > > P.S. Actually, for this particular problem, just deleting the statistics > would be fine. I've tried doing: > > alter table maindb_astobject alter column survey_id set statistics 0; > > And then analyzing the column, but when "statistics" for a column are set > to 0, Postgres seems to leave the current statistics in place, which is not > the right thing for me at all. I can successfully set "statistics" to 1, > but that turns out to be one statistic too many. > > I've tried settings the statistics via the table "pg_stats", but that turns > out to be a view, and Postgres won't allow to me to alter it. > > Perhaps I can achieve the end by altering the "pg_statistic" table instead, > but that table is more than a bit opaque to me. > > P.P.S The Seq Scan is 2-4 orders of magnitude slower than the Index Scan. >
