Hi Craig Thanks for the answer. I also thought about this. You mean something like this? SELECT reltuples FROM pg_class WHERE relname = 'mytable'; 182820 (rows) That seams reasonably fast compared to count(*). But I'm hesitating to use ANALYZE for two reasons: 1. It's very slow: it repeadly takes 59000 ms on my machine. 2. There's an autovacuum background process which already does the job, doesn't it? Yours, Stefan 2011/5/29 Craig Ringer <craig@xxxxxxxxxxxxxxxxxxxxx>: > On 05/29/2011 05:45 AM, Stefan Keller wrote: >> >> Hi, >> >> That's my solution candidate: >> >> CREATE OR REPLACE FUNCTION isnotempty() RETURNS boolean AS ' >> Â SELECT (count(*) = 1) >> Â FROM (SELECT osm_id FROM planet_osm_point LIMIT 1 OFFSET 100000) tmp >> ' LANGUAGE SQL; > > LIMIT and OFFSET are often no more efficient than count(*). You're still > likely to need a full table scan. > > Here's how I'd do it: I'd ANALYZE the table, then check the table statistics > to see that they looked to be within reasonable bounds. That way you not > only check the import, but in the process you ensure the statistics used by > the query planner are up to date. Since ANALYZE only tests a sampling of > records it does pretty much what you want, something that it's not so easy > to do in SQL. > > -- > Craig Ringer > -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
