Put an index on time_stamp (I assume there is one on id_signal already)
On 10/15/2012 12:44 PM, Pedro Jiménez wrote:
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....
Any help?
Regards.
