Re: Very big insert/join performance problem (bacula)

Marc Cousin wrote:
> This mail contains the asked plans :
> Plan 1
> around 1 million records to insert, seq_page_cost 1, random_page_cost 4

> -> Hash (cost=425486.72..425486.72 rows=16746972 width=92) (actual time=23184.196..23184.196 rows=16732049 loops=1)
> -> Seq Scan on path (cost=0.00..425486.72 rows=16746972 width=92) (actual time=0.004..7318.850 rows=16732049 loops=1)

> -> Hash (cost=1436976.15..1436976.15 rows=79104615 width=35) (actual time=210831.840..210831.840 rows=79094418 loops=1)
> -> Seq Scan on filename (cost=0.00..1436976.15 rows=79104615 width=35) (actual time=46.324..148887.662 rows=79094418 loops=1)

This doesn't address the cost driving plan question, but I think it's a
bit puzzling that a seq scan of 17M 92-byte rows completes in 7 secs,
while a seqscan of 79M 35-byte rows takes 149secs. It's about 4:1 row
ratio, less than 2:1 byte ratio, but a 20:1 time ratio. Perhaps there's
some terrible bloat on filename that's not present on path? If that seq
scan time on filename were proportionate to path this plan would
complete about two minutes faster (making it only 6 times slower instead
of 9 :).

--
-Devin