From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Bill Moran <wmoran(at)collaborativefusion(dot)com> |
Cc: | tarcizioab(at)c3sl(dot)ufpr(dot)br, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Difference between "Explain analyze" and "\timing" |
Date: | 2008-07-31 01:06:38 |
Message-ID: | 26508.1217466398@sss.pgh.pa.us |
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Lists: | pgsql-performance |
Bill Moran <wmoran(at)collaborativefusion(dot)com> writes:
> tarcizioab(at)c3sl(dot)ufpr(dot)br wrote:
>> The commands "\timing" and "EXPLAIN ANALYZE" return values related to the
>> time of execution of the instruction. These values are "Time:" and "Total
>> runtime:" respectively. What is the difference between these values, and
>> the specific use of each command in queries?
> The time reported by explain will be the time it took the server to
> execute the query.
> The time reported by \timing is the time it takes the client (psql) to
> get the result. This will be the time the server took, plus any network
> delays and time required to process the query and result on the client
> side.
Also realize that explain analyze only reports the time to *execute*
the query. Not counted are the time to parse and plan the query
beforehand and prepare the explain output afterwards. But psql's number
is the whole round-trip time and so includes all that stuff.
If any of this seems confusing, you might find it worth reading
this overview of the Postgres system structure:
http://www.postgresql.org/docs/8.3/static/overview.html
regards, tom lane
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