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Date: Fri, 23 Oct 2009 22:43:59 +0000 (UTC)
From: "Tony Brusseau (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
Subject: [jira] Commented: (DERBY-4422) Extremely slow subqueries when
 subquerying on strings
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    [ https://issues.apache.org/jira/browse/DERBY-4422?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12769505#action_12769505 ] 

Tony Brusseau commented on DERBY-4422:
--------------------------------------

 Step 1: I don't think this is a compilation issue since I originally noticed the problem when executing prepared statements.


> 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
>         Attachments: tmp2.sql
>
>
> 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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