Re: Very slow left outer join

On May 29, 2007, at 19:16 , Tyrrill, Ed wrote:

> -----
> Hash Join (cost=361299.50..1054312.92 rows=34805 width=8) (actual
> time=1446.861..368723.597 rows=2789 loops=1)
> Hash Cond: ("outer".record_id = "inner".record_id)
> -> Seq Scan on backupobjects (cost=0.00..429929.79 rows=13136779
> width=8) (actual time=5.165..359168.216 rows=13136779 loops=1)
> -> Hash (cost=360207.21..360207.21 rows=436915 width=8) (actual
> time=820.979..820.979 rows=2789 loops=1)
> -> Bitmap Heap Scan on backup_location
> (cost=3831.20..360207.21 rows=436915 width=8) (actual
> time=797.463..818.269 rows=2789 loops=1)
> Recheck Cond: (backup_id = 1071)
> -> Bitmap Index Scan on backup_location_bid
> (cost=0.00..3831.20 rows=436915 width=0) (actual time=59.592..59.592
> rows=2789 loops=1)

Off the cuff, when was the last time you vacuumed or ran ANALYZE?
Your row estimates look off by a couple orders of magnitude. With up-
to-date statistics the planner might do a better job.

As for any other improvements, I'll leave that to those that know
more than I. :)

Michael Glaesemann
grzm seespotcode net