John A Meinel <john@arbash-meinel.com> writes:
> Joel Fradkin wrote:
>> Postgres was on the second run
>> Total query runtime: 17109 ms.
>> Data retrieval runtime: 72188 ms.
>> 331640 rows retrieved.
> How were you measuring "data retrieval time"?
I suspect he's using pgadmin. We've seen reports before suggesting that
pgadmin can be amazingly slow, eg here
http://archives.postgresql.org/pgsql-performance/2004-10/msg00427.php
where the *actual* data retrieval time as shown by EXPLAIN ANALYZE
was under three seconds, but pgadmin claimed the query runtime was 22
sec and data retrieval runtime was 72 sec.
I wouldn't be too surprised if that time was being spent formatting
the data into a table for display inside pgadmin. It is a GUI after
all, not a tool for pushing vast volumes of data around.
It'd be interesting to check the runtimes for the same query with
LIMIT 3000, ie, see if a tenth as much data takes a tenth as much
processing time or not. The backend code should be pretty darn
linear in this regard, but maybe pgadmin isn't.
regards, tom lane
