Re: Why the optimizer is not choosing the best plan?
- From: Sami Seerangan <dba.orcl@xxxxxxxxx>
- To: Antonio Belloni <toni_belloni@xxxxxxxxxxxx>
- Date: Wed, 20 Oct 2004 16:39:40 -0400
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@xxxxxxxxxxxx> 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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