Re: Timing of 'SELECT 1'

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От Bruce Momjian
Тема Re: Timing of 'SELECT 1'
Дата
Msg-id 200403101642.i2AGgwQ16126@candle.pha.pa.us
обсуждение исходный текст
Ответ на Re: Timing of 'SELECT 1'  ("Merlin Moncure" <merlin.moncure@rcsonline.com>)
Ответы Re: Timing of 'SELECT 1'  (Andreas Pflug <pgadmin@pse-consulting.de>)
Список pgsql-hackers
Merlin Moncure wrote:
> Bruce Momjian wrote:
> > I am timing small queries, and found that a PREPARE/EXECUTE of "SELECT
> > 1" takes about 1.2ms on my machine.  A normal SELECT doesn't take much
> > longer, so I am wondering why a simpler query isn't faster.
> > 
> > Looking at log_executor_stats, I see the following.  Execute shows
> > nothing taking much time, mostly < .2ms, but the total seems high.  I
> > wonder if one of our standard query start/stop functions is taking too
> > long and can be optimized.
> 
> There seems to be a 'PostgreSQL ping' time of about 1-2 ms in best case
> conditions which limits the amount of queries you can fire off in 1
> second, no matter how simple.  In certain rare cases this is something
> of a bottleneck.  In my personal case it would be nice to see that time
> lower because converted COBOL applications tend to generate a lot of
> 'simple' queries.

Yes, most of that might be network time.  I am using log_duration, which
I think just tests backend time, not network transfer time, but I might
be wrong.  I want to look into this as it seems no one knows the answer.

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
359-1001+  If your life is a hard drive,     |  13 Roberts Road +  Christ can be your backup.        |  Newtown Square,
Pennsylvania19073
 


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