It has nothing to do with autocommit and everything to do with batching them together.
For instance, if you run ten update queries in autocommit mode I would expect it to take exactly the same time as:
Begin
Exec Query1
Commit
…
Begin
Exec Query10
Commit
From: pgsql-general-owner@postgresql.org [mailto:pgsql-general-owner@postgresql.org] On Behalf Of Szymon Guz Sent: Thursday, April 07, 2011 2:00 PM To: pgsql-general@postgresql.org Subject: [GENERAL] why autocommit mode is slow?
Hi,
this is maybe a stupid question, but I don't know how to explain to my coworkers why performing many inserts in autocommit mode is so much slower than making all of them in one transaction.