Re: FIRST_ROWS (is is a good idea)

From: Svend Jensen <svend.jensen_at_it.dk>
Date: Mon, 02 Sep 2002 18:44:29 +0100
Message-ID: <3D73A37D.3020308@it.dk>

Epicentre team A wrote:

> Hello,
>
> Which are the dangers of FIRST_ROWS, what possible problems on my
> datawarehouse ?
> Oracle Version = 8.1.7.0
>
> Thanks
> Oraclion
>

FIRST_ROWS favors index lookup and nested loop,

as that generally produces the first row quick.

ALL_ROWS favor hash/sort/merge joins and full/index scans, if hash_join_enabled=true in init.ora.
Note that you must have a decent hash_area_size (memory usage for every session!). Default is twice sort_area_size. A bit small maybe? Received on Mon Sep 02 2002 - 12:44:29 CDT