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From "Tony Brusseau (JIRA)" <j...@apache.org>
Subject [jira] Created: (DERBY-4422) Extremely slow subqueries when subquerying on strings
Date Fri, 23 Oct 2009 17:38:59 GMT
Extremely slow subqueries when subquerying on strings
-----------------------------------------------------

                 Key: DERBY-4422
                 URL: https://issues.apache.org/jira/browse/DERBY-4422
             Project: Derby
          Issue Type: Bug
    Affects Versions: 10.5.3.0
         Environment: Suse Unix 10.3.
            Reporter: Tony Brusseau


SELECT DISTINCT C.INTERNAL_ID 
FROM OC_CONCEPTS C
WHERE
   (C.INTERNAL_ID IN (SELECT DISTINCT OCS.CONCEPT_ID FROM OC_CONCEPT_STRINGS OCS WHERE OCS.CONCEPT_ID=1))

Both queries above are trivial and they are both acting on fully indexed primary key columns.
This query runs just fine. 

However, when I make the small modification of searching on an indexed text column in the
sub query, it takes over 6 seconds to run, even though both queries independently take <
1ms run.

SELECT DISTINCT C.INTERNAL_ID 
FROM OC_CONCEPTS C
WHERE
   (C.INTERNAL_ID IN (SELECT DISTINCT OCS.CONCEPT_ID FROM OC_CONCEPT_STRINGS OCS WHERE OCS.NL_LC
= 'dash'))


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