| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Dave Smith <dave(dot)smith(at)candata(dot)com> |
| Cc: | Martijn van Oosterhout <kleptog(at)svana(dot)org>, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Using IN with subselect |
| Date: | 2004-11-25 17:57:01 |
| Message-ID: | 796.1101405421@sss.pgh.pa.us |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-general |
Dave Smith <dave(dot)smith(at)candata(dot)com> writes:
> Well here is explain. I would guess that it is executed each time ..
> function any different?
> HashAggregate (cost=288.32..288.32 rows=1 width=32)
> -> Hash IN Join (cost=288.18..288.31 rows=1 width=32)
> -> Subquery Scan journal_all (cost=282.36..282.45 rows=2 width=64)
> -> Hash (cost=5.83..5.83 rows=1 width=13)
> -> Index Scan using glmast_index3 on glmast (cost=0.00..5.83 rows=1 width=13)
No ... this plan says to scan glmast once, load the selected rows into
an in-memory hash table, then scan journal_all once and probe the hash
table for matches. It looks like a pretty decent choice of plan to me.
regards, tom lane
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Tom Lane | 2004-11-25 18:02:21 | Re: How can I change a cast from explicit only to implicit? |
| Previous Message | Martijn van Oosterhout | 2004-11-25 17:25:46 | Re: Using IN with subselect |