| From: | Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> |
|---|---|
| To: | Vadim Mikheev <vadim(at)krs(dot)ru> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgreSQL(dot)org |
| Subject: | Re: [HACKERS] Idea for speeding up uncorrelated subqueries |
| Date: | 1999-08-06 02:35:32 |
| Message-ID: | 199908060235.WAA21544@candle.pha.pa.us |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
> Bruce Momjian wrote:
> >
> > Yes, the subqueries need work. We don't even do index lookups into the
> > inner plan, only sequential. Already on TODO. The multiple query
> ^^^^^^^^^^^^^^^
> What? Indices are used when appropriate.
Sorry, bad wording. My English should be better. :-)
I meant to say that joins from the outer plan to subplan are always
nested loops, not hash or mergejoins. If you have something like:
delete from tab where col in (select col2 from largetable)
it takes a long time, when it really should be quick. That is why
people are encouraged to use EXISTS.
--
Bruce Momjian | http://www.op.net/~candle
maillist(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Vadim Mikheev | 1999-08-06 03:04:38 | Re: [HACKERS] Idea for speeding up uncorrelated subqueries |
| Previous Message | Vadim Mikheev | 1999-08-06 02:12:10 | Re: [HACKERS] Idea for speeding up uncorrelated subqueries |