Hello Herald,
the queried table is used for communication between server application and
web user interface.
When application detects an event it writes it down in table.
The web client checks every 10 second if something new is written in the
table.
Usually nothing new is written but the client has to check it.
I don't fetch all rows, usually just the last one written.
The speed of the query is not a problem but the strange thing is the
processor load with postmaster when the query is executed.
I dont now how to reduce processor load.
Should I change some other settings beside shared_buffers like work_mem?
Or maybe such processor load is OK?
Regards,
Maja
> Hello Maja,
>
>> EXPLAIN ANALYSE SELECT * FROM system_alarm WHERE id_camera='3' AND
>> confirmed='false' AND dismissed='false' ORDER BY date DESC, time DESC
>> LIMIT 1;
>>
>> (the table is indexed by id_camera, has around 1 milion rows, and this
>> query returns around 700000 rows and is executed (EXPLAIN ANALYSE) in
>> around 4800 ms, and this table is queried a lot although not so often
>> queried modified)
>
> 700.000 of 1.000.000 rows is around 70% ... that are nearly all rows.
> As much as I read you, this table is not often modified. What reason
> is there for quering all that data again and again instead of keeping
> it in memory (should it be really needed) ?
>
>
> Harald
>
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