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From "Anurag Shekhar (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-3330) provide support for unique constraint over nullable columns
Date Tue, 29 Jan 2008 11:19:34 GMT

    [ https://issues.apache.org/jira/browse/DERBY-3330?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12563473#action_12563473
] 

Anurag Shekhar commented on DERBY-3330:
---------------------------------------

Thanks Mike for pointing out issues related to locking and also about the way 
I have handled deleted row.

I went through the code you have have asked me to look for reference and also the doIns code.
This is what I think I should be doing.

Step 1. Find the slot where new row can be inserted.
Step 2. Get the left row (without checking for deleted row) if there is a match try to 
hold a lock. If lock is obtained without releasing the latch no other transaction is 
working on it and it should be a deleted row. return error if its not. 
If latch was released tree has under gone some changes and start with step 1.

Step3. Repeat step 2 for right row.

I am checking out B2IRowLocking3.searchLeftAndLockPreviousKey and will be
 posting about locking scheme and effect of isolation level shortly.

> 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: derby-3330-testcase.diff, derby-3330.diff, derby-3330v2.diff, derby-3330v3.diff,
derby-3330v4.diff, FunctionalSpec_DERBY-3330-V2.html, FunctionalSpec_DERBY-3330.html
>
>
> Allow unique constraint over nullable field. Right now derby support unique constraint
only over not null columns.

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