| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "john cartmell" <john(dot)cartmell(at)mediaburst(dot)co(dot)uk> |
| Cc: | pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: ORDER BY ... LIMIT.. performance |
| Date: | 2002-12-05 22:00:09 |
| Message-ID: | 2707.1039125609@sss.pgh.pa.us |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-performance |
"john cartmell" <john(dot)cartmell(at)mediaburst(dot)co(dot)uk> writes:
> Without the LIMIT clause the query takes approximately 3-5 seconds to
> return.
> If total number of rows returned without the LIMIT clause is greater
> than 20 records, then the above query also takes th same amount of time.
> But if the the total number of rows is 20 or less then the time taken
> for the above query to return goes up to 20-30 seconds.
What does EXPLAIN (or better EXPLAIN ANALYZE) show for these various
cases? Evidently the planner is shifting to a different plan because
of the small LIMIT, but with no details it's hard to say anything
useful.
regards, tom lane
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Jochem van Dieten | 2002-12-05 22:05:57 | Re: Is a better way to have the same result of this query? |
| Previous Message | Vernon Wu | 2002-12-05 21:23:16 | Re: Is a better way to have the same result of this query? |