| From: | "Timothy H(dot) Keitt" <keitt(at)nceas(dot)ucsb(dot)edu> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Andrew McMillan <Andrew(at)catalyst(dot)net(dot)nz>, Nathan Barnett <nbarnett(at)cellularphones(dot)com>, "'Stephan Szabo'" <sszabo(at)kick(dot)com>, pgsql-general(at)postgreSQL(dot)org |
| Subject: | Re: Statistical Analysis |
| Date: | 2000-07-25 01:46:12 |
| Message-ID: | 397CF164.7034DBEF@nceas.ucsb.edu |
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| Thread: | |
| Lists: | pgsql-general |
Tom Lane wrote:
>
> Note that this isn't necessarily going to fix your performance problem,
> since a scan of the whole input table is still going to be required.
> But if the expensive processing was somewhere downstream of that basic
> scan, it should help.
>
The only way that I know of to do this fast is to insert the items in
random order. I've done this (in C++, not postgres) using a map
(b-tree) data structure: insert key-value pairs with the key being a
random number; then pop entries off the tail of the map as needed.
Tim
--
Timothy H. Keitt
National Center for Ecological Analysis and Synthesis
735 State Street, Suite 300, Santa Barbara, CA 93101
Phone: 805-892-2519, FAX: 805-892-2510
http://www.nceas.ucsb.edu/~keitt/
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