[Bizgres-general] Problem with EXPLAIN Plan

[Jie Zhang]

Milen,

Can you let me know which version of bizgres you are running -- bizgres0.9
or the cvs tip? The implementation on the cvs tip should be much faster.

Thanks,
Jie

On 6/15/06 3:53 PM, "Mark Kirkwood" <mkirkwood at greenplum.com> wrote:

> Milen Kulev wrote:
>> 
>> Another Problem is the pretty high BITMAP index creation times. Details:
>> 
>>  bizdb=# CREATE INDEX  idx_countries_id_bmp_ ON fact using bitmap
>> (country_id)  ;
>> CREATE INDEX
>> Time: 67401.643 ms
>> bizdb=# CREATE INDEX  idx_times_id_bmp_ ON fact using bitmap (time_id)  ;
>> CREATE INDEX
>> Time: 96333.344 ms
>> bizdb=# CREATE INDEX  idx_products_id_bmp_ ON fact using bitmap (product_id)
>> ;
>> CREATE INDEX
>> Time: 814897.540 ms
>> bizdb=# CREATE INDEX  idx_customers_id_bmp_ ON fact using bitmap
>> (customer_id)  ;
>> CREATE INDEX
>> Time: 239735.302 ms
>> 
>>   
> 
> (I was a bit quick with the 'send' key....)
> 
> It is probably interesting to find out the # of distinct values for the
> various indexed columns,
> as in general a higher # of distinct values will make the bitmap index
> take longer to create.
> 
> At a glance (and checking the on disk sizes of the bitmap index
> relation), I would guess:
> 
> - country_id has a low # of distinct values
> - product_id has a high # of distinct values
> 
> In terms of speeding this up, try increasing the maintenance_work_mem
> postgresql.conf parameter!
> 
> Cheers
> 
> Mark
> 
> 
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