Re: Always_semi_join

hash always requires a full table scan. So you use hash's when you need to return large amounts of data from each and/or there are large differences in sizes of the two tables.

you can set always_semi_join with alter session and from EXECUTE IMMEDIATE.

chage it as needed.
>
> From: "Ramon E. Estevez" <restevez_at_blh.com.do>
> Date: 2003/05/20 Tue AM 11:06:41 EDT
> To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> Subject: Always_semi_join
>
> Hi List,
>
> I change the parameter ALWAYS_SEMI_JOIN to HASH in a DB and ran a report
> and last forever,
> In another DB, without the parameter, ran in 12 seconds. This was the
> only process that was
> Affected with the parameter.
>
> Why a FTS if I am using a index in the where clause, will the DB ALWAYS
> use that method.
>
> Kind of confused.
>
> TIA
>
> **---
> BD WITH ALWAYS_SEMI_JOIN=STANDARD
> **---
> QUERY_PLAN
> ------------------------------------------------------------------------
> --
> SORT ORDER BY
> FILTER
> NESTED LOOPS
> NESTED LOOPS
> TABLE ACCESS BY INDEX ROWID TPLA_ACCRUAL
> INDEX RANGE SCAN CP01CAP_ACC
> TABLE ACCESS BY INDEX ROWID TPLA_CUENTA
> INDEX UNIQUE SCAN CP01PLA_PDA
> TABLE ACCESS BY INDEX ROWID TCLI_PERSONA
> INDEX UNIQUE SCAN CP01CLI_CLI
> FILTER
> INDEX RANGE SCAN CP01CAP_ACC
>
> 12 rows selected.
>
> ************************************************
> **---
> BD WITH ALWAYS_SEMI_JOIN=HASH
> **---
> QUERY_PLAN
> ------------------------------------------------------------------------
> ---
> SORT ORDER BY
> MERGE JOIN CARTESIAN
> HASH JOIN
> TABLE ACCESS BY LOCAL INDEX ROWID TPLA_ACCRUAL
> INDEX RANGE SCAN CP01CAP_ACC
> HASH JOIN
> TABLE ACCESS FULL TPLA_CUENTA
> TABLE ACCESS FULL TCLI_PERSONA
> SORT JOIN
> INDEX RANGE SCAN CP01CAP_ACC
>
> 10 rows selected.
>
>
>
> Ramon E. Estevez
> restevez_at_blh.com.do
> 809-535-8994
>
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: Ramon E. Estevez
> INET: restevez_at_blh.com.do
>
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