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From "Satheesh Bandaram (JIRA)" <derby-...@db.apache.org>
Subject [jira] Created: (DERBY-772) Handle pushing IN predicates into UNIONs. This would allow use of index if present improving performance.
Date Sat, 17 Dec 2005 22:02:34 GMT
Handle pushing IN predicates into UNIONs. This would allow use of index if present improving
performance.
---------------------------------------------------------------------------------------------------------

         Key: DERBY-772
         URL: http://issues.apache.org/jira/browse/DERBY-772
     Project: Derby
        Type: Sub-task
  Components: SQL  
    Versions: 10.0.2.0, 10.1.2.1, 10.2.0.0    
 Environment: generic
    Reporter: Satheesh Bandaram
     Fix For: 10.2.0.0, 10.1.2.2


While fix for DERBY-649 allows pushing binary predicates into SELECT statements that are underneath
a UNOIN, it would also be good to allow IN operations to be pushed. Derby can rewrite IN operations
in a way to allow use of index, if present.

Derby currently rewrites: REF IN (1, 2, 3) to REF >=1 and REF <=3 and hence would allow
use of index on REF, if present. Pushing this predicate into Union would allow use of index
on REF for queries like:

Select * from 
     (SELECT REF, NAME from T1 UNION ALL SELECT REF, NAME from t2)
where REF IN (1,2,3)

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