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From "A B (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-3456) Allow removing not null from collumns particpating in unique constraint.
Date Wed, 27 Feb 2008 18:41:51 GMT

    [ https://issues.apache.org/jira/browse/DERBY-3456?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12573017#action_12573017

A B commented on DERBY-3456:

When creating the backing index for a constraint, Derby currently attempts to share conglomerates
if there is an existing conglomerate such that:

  1. the set of columns and their order in the constraint-backing index is the same
    as that of an existing index AND

  2. the ordering attributes are the same AND

  3. both the already-existing index and the constraint-backing index being created
    are non-unique OR the already existing index is unique

If all three of these conditions are true then Derby will use a single physical conglomerate
to support the already-existing index and the new constraint-backing index.

So my question is: when unique constraints over nullable columns are introduced, will this
criteria (found in CreateIndexConstantAction.java; search for "shareExisting") need to be
updated?  In particular, I'm wondering if #3 is still good enough, or will additional logic
for nullable unique constraints need to be added?

> Allow removing not null from collumns particpating in unique constraint.
> ------------------------------------------------------------------------
>                 Key: DERBY-3456
>                 URL: https://issues.apache.org/jira/browse/DERBY-3456
>             Project: Derby
>          Issue Type: Sub-task
>          Components: SQL, Store
>    Affects Versions:
>         Environment: all
>            Reporter: Anurag Shekhar
>            Assignee: Anurag Shekhar
>         Attachments: derby-3456v1.diff, upgradetests.diff

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