maria-developers team mailing list archive

[Sergey Petrunya <psergey@xxxxxxxxxxxx>]

Hello Igor,

On Thu, Jul 01, 2010 at 11:55:58PM -0700, Igor Babaev wrote:
> According to our agreement I introduced a new flag for MRR.
> I called it HA_MRR_MATERIALIZED_KEYS. This flag passed to any MMR
> interface function that takes mrr_mode as a parameter says:
> key values used in ranges are materialized in some buffers external to MRR.
> 

This patch only gives DS-MRR information that the keys are materialized.
However, DS-MRR needs to work on (key, range_id) pairs. The patch doesn't
allow to assoicate key with range_id (or vice versa), so DS-MRR will have to
keep (key_pointer, range_id) tuples.

If we consider 64-bit environment, then sizeof(key_value_pointer)==
sizeof(key_value), and this patch won't bring any benefit at all.

I was expecting that the patch will provide some means to associate
key_value_pointer with range_id, so that DS-MRR won't need to store both.

Can we discuss this on scrum meeting or Monday evening?

> === modified file 'sql/handler.h'
> --- sql/handler.h	2010-03-20 12:01:47 +0000
> +++ sql/handler.h	2010-07-01 20:00:35 +0000
> @@ -1212,6 +1212,12 @@ void get_sweep_read_cost(TABLE *table, h
>  */
>  #define HA_MRR_NO_NULL_ENDPOINTS 128
>  
> +/*
> +  The MRR user has materialized range keys somewhere in the user's buffer.
> +  This can be used for optimization of the procedure that sorts these keys
> +  since in this case key values don't have to be copied into the MRR buffer.
> +*/
> +#define HA_MRR_MATERIALIZED_KEYS 256
>  
>  
>  /*
> 
> === modified file 'sql/sql_join_cache.cc'
> --- sql/sql_join_cache.cc	2010-03-07 15:41:45 +0000
> +++ sql/sql_join_cache.cc	2010-07-01 19:59:55 +0000
> @@ -651,6 +651,9 @@ int JOIN_CACHE_BKA::init()
>  
>    use_emb_key= check_emb_key_usage();
>  
> +  if (use_emb_key)
> +    mrr_mode|= HA_MRR_MATERIALIZED_KEYS;
> +
>    create_remaining_fields(FALSE);
>  
>    set_constants();
> @@ -2617,6 +2620,8 @@ int JOIN_CACHE_BKA_UNIQUE::init()
>        data_fields_offset+= copy->length;
>    } 
>  
> +  mrr_mode|= HA_MRR_MATERIALIZED_KEYS;
> +
>    DBUG_RETURN(rc);
>  }
>  
> 

BR
 Sergey
-- 
Sergey Petrunia, Software Developer
Monty Program AB, http://askmonty.org
Blog: http://s.petrunia.net/blog