optimize mysql count query

Question

Is there a way to optimize this further or should I just be satisfied that it takes 9 seconds to count 11M rows ?

devuser@xcmst > mysql --user=user --pass         


        

Answer 1

If the historical data is not volatile, create a summary table. There are various approaches, the one to choose will depend on how your table is updated, and how often.

For example, assuming old data is rarely/never changed, but recent data is, create a monthly summary table, populated for the previous month at the end of each month (eg insert January's count at the end of February). Once you have your summary table, you can add up the full months and the part months at the beginning and end of the range:

select count(*) 
from record_updates 
where date_updated >= '2009-10-11 15:33:22' and date_updated < '2009-11-01';

select count(*) 
from record_updates 
where date_updated >= '2010-12-00';

select sum(row_count) 
from record_updates_summary 
where date_updated >= '2009-11-01' and date_updated < '2010-12-00';

I've left it split out above for clarity but you can do this in one query:

select ( select count(*)
         from record_updates 
         where date_updated >= '2010-12-00'
               or ( date_updated>='2009-10-11 15:33:22' 
                    and date_updated < '2009-11-01' ) ) +
       ( select count(*) 
         from record_updates 
         where date_updated >= '2010-12-00' );

You can adapt this approach for make the summary table based on whole weeks or whole days.