On Wed, Oct 17, 2012 at 6:14 AM, Pedro Jiménez Pérez <p.jime...@ismsolar.com > wrote:
> select var_value from ism_floatvalues where id_signal = 29660 order by > time_stamp desc limit 1; > > This is what EXPLAIN returns (can't make EXPLAIN ANALYZE because it > "never" ends): > > "Limit (cost=0.00..258.58 rows=1 width=16)" > " -> Index Scan Backward using ism_floatvalues_index_time_stamp on > ism_floatvalues (cost=0.00..8912076.82 rows=34466 width=16)" > " Filter: (id_signal = 29660)" > > This is EXPLAIN ANALYZE without "limit 1": Add (or modify the existing) an index on id_signal, time_stamp desc, and you're done. It must be a case of descending time stamps not hitting the filter condition (id_signal) soon enough.
