timing != log duration

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Hello

I am wondering why the time reported by \timing in psql is not the same
as the time reported by duration in the log file when log_duration or
log_min_duration_statement are on?. I can not find any information about
this in the documentation.

e.g.
- -----------------------------------
ver=# SELECT * from version ;
Time: 0.450 ms

2012-03-20 16:10:16 CET 29119 LOG: duration: 0.313 ms statement:
SELECT * from version ;
- -----------------------------------

ver=# PREPARE foo AS SELECT * from version ;
PREPARE
Time: 0.188 ms

ver=# EXECUTE foo;
Time: 0.434 ms

ver=# DEALLOCATE foo;
DEALLOCATE
Time: 0.115 ms

2012-03-20 16:12:21 CET 29119 LOG: duration: 0.127 ms statement:
PREPARE foo AS SELECT * from version ;
2012-03-20 16:12:37 CET 29119 LOG: duration: 0.303 ms statement:
EXECUTE foo;
2012-03-20 16:13:24 CET 29119 LOG: duration: 0.055 ms statement:
DEALLOCATE foo;
- -----------------------------------

Thanks in advance
regards,
- --
Rafael Martinez Guerrero
Center for Information Technology
University of Oslo, Norway

PGP Public Key: http://folk.uio.no/rafael/
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