Re: best way to query

Tom Lane wrote:
> Steve Clark <sclark@netwolves.com> writes:
>
>>Tom Lane wrote:
>>
>>>Also, whatever is the ORDER BY for?
>
>
>>without the order by it wants to do a seq scan of t_unit_event_log.
>>see below:
>>  explain select count(*) from t_event_ack_log where event_log_no not
>>in (select event_log_no from t_unit_event_log);
>>                                        QUERY PLAN
>>----------------------------------------------------------------------------------------
>>  Aggregate  (cost=12144872193.82..12144872193.82 rows=1 width=0)
>>    ->  Seq Scan on t_event_ack_log  (cost=0.00..12144871485.07
>>rows=283497 width=0)
>>          Filter: (NOT (subplan))
>>          SubPlan
>>            ->  Seq Scan on t_unit_event_log  (cost=0.00..40286.56
>>rows=1021156 width=4)
>>(5 rows)
>
>
> Hmm, the big problem with that isn't the seqscan but the lack of a
> Materialize step to buffer it; which says to me that you're running a
> pretty old Postgres version (8.0 or older).  You should think about an
> update if you're running into performance issues.
>
>             regards, tom lane
>
>

Hi Tom,

Actually this is

  show server_version;
  server_version
----------------
  8.2.5


On FreeBSD 6.2

And Daniel gave me a query that does the job in just a few seconds.


Thanks,
Steve