Wrong Results from Query Rewrite

Hi,

Oracle 10.2.0.4 on Solaris 9

We have noticed wrong results occuring during query rewrite involving table 1 and table 2. Each of these tables have a MV. This problem is noticed only when a sub query is employed for the IN operator. Here is sample query:

Query 1 -

SQL>SELECT COUNT(1) FROM tab1
WHERE END_EFF_DATE=TO_DATE('31-DEC-9999','DD-MON-YYYY')  
  AND RECIP_ID IN (SELECT RECIP_ID FROM tab2
                   WHERE END_EFF_DATE=TO_DATE('31-DEC-9999','DD-MON-YYYY')  
                     AND RELATIONSHIP_IND IN ('04','05')
                  ); 
COUNT(1)

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3015026

The result is different (and correct) when the distinct is used in the sub query as below -