Need help with performance for very very huge tables...

Question

Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production.
My DB has many tables and out of which I am interested in getting data from product and sales.
select /*parallel 32*/count(1) from (
select /*parallel 32*/distinct prod_code from product pd, sales s
where pd.prod_opt_cd is NULL
and s.sales_id = pd.sales_id
and s.creation_dts between to_date ('2012-07-01','YYYY-MM-DD') and
to_date ('2012-07-31','YYYY-MM-DD')
More information -
Total Rows in sales table - 18001217
Total rows in product table - 411800392
creation_dts dont have index on it.
I started query in background but after 30 hours I saw the error saying -
ORA-01555: snapshot too old: rollback segment number 153 with name
Is there any other way to get above data in optimized way?

Answer 1

Formatting your query a bit (and removing the hints), it evaluates to:
SELECT COUNT(1)
FROM  (SELECT DISTINCT prod_code
       FROM   product pd
              INNER JOIN sales s
              ON s.sales_id = pd.sales_id 
       WHERE  pd.prod_opt_cd is NULL
       AND    s.creation_dts BETWEEN TO_DATE('2012-07-01','YYYY-MM-DD')
                                 AND TO_DATE('2012-07-31','YYYY-MM-DD')
      );This should be equivalent to
SELECT COUNT(DISTINCT prod_code)
FROM   product pd
       INNER JOIN sales s
       ON s.sales_id = pd.sales_id 
WHERE  pd.prod_opt_cd is NULL
AND    s.creation_dts BETWEEN TO_DATE('2012-07-01','YYYY-MM-DD')
                          AND TO_DATE('2012-07-31','YYYY-MM-DD');On the face of it, that's a ridiculously simple query If s.sales_id and pd.sales_id are both indexed, then I don't see why it would take a huge amount of time. Even having to perform a FTS on the sales table because creation_dts isn't indexed shouldn't make it a 30-hour query. If either of those two is not indexed, then it's a much uglier prospect in joining the two tables. However, if you often join the product and sales tables (which seems likely), then not having those fields indexed would be contraindicated.