2012/10/15 Pedro Jiménez <p.jime...@ismsolar.com>: > Hello, > I'm trying to do a simple SQL query over Postgresl 9.0 running on Ubuntu. > > I have a large table (over 100 million records) with three fields, id_signal > (bigint), time_stamp (timestamp) and var_value (float). > > My query looks like this: > > select var_value from ism_floatvalues where id_signal = 29660 order by > time_stamp desc limit 1; > > So I want to select the last value from a determinated ID (is_signal). > > This query runs FOREVER, while if I delete "limit 1" it runs instantly....
did you ANALYZE your tables? Can you send EXPLAIN ANALYZE result of both queries? Regards Pavel Stehule > > Any help? > > Regards. > > > > > -- > Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-performance -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
