"Tom Lane" <tgl@sss.pgh.pa.us> writes:
> "Gregor Roessle" <g.roessle@osram.de> writes:
>> The Server hangs when executing a query like this:
>
>> select * from messwerte where pknr = 28315178 and isproducing = 't' order by
>> timestamp desc limit 1;
>
> I seriously doubt that it's hung. Takes a long time, maybe so. Is it
> trying to use an indexscan on timestamp to substitute for a sort step?
Surely it wouldn't make 32ms become long enough to qualify as "hung".
Unless perhaps it's otherwise using an index on pknr and/or isproducing and
with the "ORDER BY timestamp desc LIMIT 1" it's using a different large index.
I think we have to see
EXPLAIN ANALYZE select * from messwerte where pknr = 28315178 and isproducing = 't' order by timestamp;
EXPLAIN ANALYZE select * from messwerte where pknr = 28315178 and isproducing = 't' limit 1;
EXPLAIN select * from messwerte where pknr = 28315178 and isproducing = 't' order by timestamp limit 1;
--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
Ask me about EnterpriseDB's On-Demand Production Tuning