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Re: Why the optimizer is not choosing the best plan?

From: Sami Seerangan <dba.orcl_at_gmail.com>
Date: Wed, 20 Oct 2004 16:39:40 -0400
Message-ID: <f09dd62804102013395d49606d@mail.gmail.com>


I have the values like below, but still it is going for NL_JOIN.

SQL> show parameter hash  

NAME                                 TYPE    VALUE
------------------------------------ ------- ------------------------------
hash_area_size                       integer 2000000
hash_join_enabled                    boolean TRUE
hash_multiblock_io_count             integer 0
SQL> show parameter join  
NAME                                 TYPE    VALUE
------------------------------------ ------- ------------------------------
always_anti_join                     string  HASH
always_semi_join                     string  HASH
hash_join_enabled                    boolean TRUE
SQL> On Wed, 20 Oct 2004 17:18:38 -0300 (ART), Antonio Belloni <toni_belloni_at_yahoo.com.br> wrote:
> Hi,
>
> If you want that Oracle consider hash joins , you
> should set the following parameters in the init.ora:
>
> HASH_JOIN_ENABLED = TRUE
> HASH_AREA_SIZE = n , where n is the amount of memory
> allocated for hash joins.
>
> Also , consider setting the following parameters:
> ALWAYS_SEMI_JOIN = HASH
> ALWAYS_ANTI_JOIN = HASH
>
> So , semi and anti join operations will be using hash
> join.
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Received on Wed Oct 20 2004 - 15:35:38 CDT

Original text of this message

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