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Re: [PATCH] Add last_executed timestamp to pg_stat_statements - Mailing list pgsql-hackers

From Christoph Berg
Subject Re: [PATCH] Add last_executed timestamp to pg_stat_statements
Date
Msg-id aYXH4hkFc_2xOa8t@msg.df7cb.de
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In response to Re[4]: [PATCH] Add last_executed timestamp to pg_stat_statements  ("Pavlo Golub" <pavlo.golub@cybertec.at>)
Responses Re[2]: [PATCH] Add last_executed timestamp to pg_stat_statements
Re: [PATCH] Add last_executed timestamp to pg_stat_statements
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Re: Pavlo Golub
> > I still wonder if "stats_last_updated" is a good name here. What about
> > "last_execution_start", since that is exactly what this timestamp is.
> 
> Yeah, sounds better really. Thanks

I still believe that storing execution start time is the wrong thing
to do as it will miss all long-running statements. Consider this
timeline:

09:55 get all stats changed since 09:50
      -> doesn't see the statement because it hasn't started yet
09:57 start long-running statement
10:00 get all stats changed since 09:55
      -> doesn't see the statement because it's still running
10:02 long-running statement terminates, storing 09:57 as timestamp
10:05 get all stats changed since 10:00
      -> doesn't see the statement because it's too old

Christoph

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