Stefan Keller wrote > So, if I'm understanding you correctly, we're talking solely about > following clause in the query you gave initially: > > WHERE doc.date_last_updated >= date(now() - '171:00:00'::interval) > which initially was > WHERE documenttype = 4 > and now is being replaced by a temporary (I'd say derived) column > WHERE updated > ? > > In any case - I have to go - but run http://explain.depesz.com/ and > give a weblink to the explain plans of your queries. Here's the query plan for the original query I struggled with: WHERE doc.date_last_updated >= date(now() - '171:00:00'::interval) The original slow query with date() <http://explain.depesz.com/d/WEy/SFfcd5esMuuI9wrLmQrZU33ma371uW2Nlh1PmeI9ZDRiAJ4wjv> Then, just out of curiosity, I replaced the WHERE condition with another one: WHERE doc.documenttype = 4. documenttype is an unindexed integer column. It's fast. Here's the query plan: date() condition replaced with documenttype = 4 <http://explain.depesz.com/d/kHG/u1dvsDyJPBK92xnKwNT3YkQsNW6WfG9aHmWAzVSOgmXikL3hiW> Then, as David suggested, I tried to precompute the doc.date_last_updated >= date(now() - '171:00:00'::interval). I created a new boolean temp_eval column on the DOCUMENT table and updated the rows like this: update "DOCUMENT" set temp_eval = date_last_updated >= date(now() - '171:00:00'::interval); Then I analyzed the table and modified the query to only have WHERE temp_eval = TRUE. I expected this to be fast, but it took 41 minutes to complete. Here's the query plan: Precomputed column <http://explain.depesz.com/d/2aFw/GLqQ8CMGDZOYx5134M8eallFluervKXDfOdnaz4nZTMXYNacji> -- View this message in context: http://postgresql.nabble.com/Query-1-000-000-slowdown-after-adding-datetime-comparison-tp5864045p5864164.html Sent from the PostgreSQL - performance mailing list archive at Nabble.com. -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
