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From Anurag shekhar <Anurag.Shek...@Sun.COM>
Subject Re: [jira] Commented: (DERBY-3330) provide support for unique constraint over nullable columns
Date Wed, 27 Feb 2008 20:40:17 GMT
Unique constraint on non nullable fields still act like a unique index 
(because there is no null value) but internally they are backed by non 
unique indexes with uniqueWhenNotNull attribute.
anurag

Mike Matrigali wrote:
> I thought from functional spec and ongoing discussion that behavior of 
> unique constraint on non-nullable columns would be unchanged.  So this
> constraint should still be backed by a unique index.
>
> Anurag Shekhar (JIRA) wrote:
>>     [ 
>> https://issues.apache.org/jira/browse/DERBY-3330?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12573032#action_12573032

>> ]
>> Anurag Shekhar commented on DERBY-3330:
>> ---------------------------------------
>>
>> dml019 test group by clause of unique constraint. When unique 
>> constraint was backed by unique index, distinct scan  was used but 
>> after making it non unique constraint this was not the case so the 
>> results are not ordered.
>> I have checked the test suite from nist web site and it mandates only 
>> number of rows and not their sequence.
>>> provide support for unique constraint over nullable columns
>>> -----------------------------------------------------------
>>>
>>>                 Key: DERBY-3330
>>>                 URL: https://issues.apache.org/jira/browse/DERBY-3330
>>>             Project: Derby
>>>          Issue Type: New Feature
>>>          Components: Store
>>>    Affects Versions: 10.4.0.0
>>>         Environment: all
>>>            Reporter: Anurag Shekhar
>>>            Assignee: Anurag Shekhar
>>>         Attachments: BTreeController.diff, derby-3330-testcase.diff, 
>>> derby-3330.diff, derby-3330v2.diff, derby-3330v3.diff, 
>>> derby-3330v4.diff, derby-3330v5.diff, derby-3330v6.diff, 
>>> derby-3330v7.diff, derby-3330v8.diff, derby-3330v9.diff, 
>>> FunctionalSpec_DERBY-3330-V2.html, FunctionalSpec_DERBY-3330.html, 
>>> UniqueConstraint_Implementation.html, 
>>> UniqueConstraint_Implementation_V2.html, 
>>> UniqueConstraint_Implementation_V3.html
>>>
>>>
>>> Allow unique constraint over nullable field. Right now derby support 
>>> unique constraint only over not null columns.
>>
>


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