Re: Could somebody EXPLAIN? :-) - Mailing list pgsql-general

From Tom Lane
Subject Re: Could somebody EXPLAIN? :-)
Date
Msg-id 16739.977415755@sss.pgh.pa.us
Whole thread Raw
In response to Could somebody EXPLAIN? :-)  (fabrizio.ermini@sysdat.it)
List pgsql-general
fabrizio.ermini@sysdat.it writes:
> All this figures confuse me. Which one should i use for
> comparison?

The reading of your stopwatch ;-)

The first line's "cost" value is the system's attempt to estimate total
runtime, but it would be foolish to take this as gospel.  Especially so
with a pre-7.0 release, as I see you are using.  There's a number of
problems with cost estimation in old releases, the biggest one for this
example being that SubPlan costs don't get factored into the outer
plan's cost.

            regards, tom lane

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