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From "Mike Matrigali (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DERBY-3330) provide support for unique constraint over nullable columns
Date Fri, 22 Feb 2008 18:23:23 GMT

     [ https://issues.apache.org/jira/browse/DERBY-3330?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Mike Matrigali updated DERBY-3330:
----------------------------------


comment on implementation details:
While creating the unique constraint null checking is now conditional (only for the older
version of Data Dictionary). In case of older version Data Dictionary the backing index created
is an unique index. 

In order to not cause performance degredation for existing unique constraints I would have
expected the constraint creation code to use the old unique index for non-null columns and
use the new index for null columns.   The unique
index is going to perform somewhat better as it will have less checking to do (for instance
on insert it will not have to
check if nulls are in the key and do extra searching).  Also it will make it likely that only
new applications that use the new
feature will see any new problems introduced by the new index.  Existing applications will
continue to use the old
code.

> 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, FunctionalSpec_DERBY-3330-V2.html, FunctionalSpec_DERBY-3330.html,
UniqueConstraint_Implementation.html
>
>
> Allow unique constraint over nullable field. Right now derby support unique constraint
only over not null columns.

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