| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> |
| Cc: | Vadim Mikheev <vadim(at)krs(dot)ru>, pgsql-hackers(at)postgreSQL(dot)org |
| Subject: | Re: [HACKERS] Idea for speeding up uncorrelated subqueries |
| Date: | 1999-08-05 16:10:45 |
| Message-ID: | 4838.933869445@sss.pgh.pa.us |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> writes:
>> Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> writes:
>>>> Yes, the subqueries need work. We don't even do index lookups into the
>>>> inner plan, only sequential. Already on TODO.
>>
>> Huh? I don't follow that at all...
> Suppose you have a subquery that returns 1000 rows. There is no code so
> lookups of the inner table are indexed:
> select *
> from tab
> where col in (select col2 from tab2)
> In this case, a sequential scan of the subquery results are required.
Well, yes, the subquery is a sequential scan. I guess what you are
envisioning is rewriting this into some kind of nested-loop join?
For simple cases that might be possible...
regards, tom lane
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Bruce Momjian | 1999-08-05 16:17:50 | Re: [HACKERS] Idea for speeding up uncorrelated subqueries |
| Previous Message | Bruce Momjian | 1999-08-05 15:48:06 | Re: [HACKERS] Idea for speeding up uncorrelated subqueries |