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From "Bryan Pendleton (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-1489) Provide ALTER TABLE DROP COLUMN functionality
Date Fri, 25 Aug 2006 14:39:23 GMT
    [ http://issues.apache.org/jira/browse/DERBY-1489?page=comments#action_12430520 ] 
            
Bryan Pendleton commented on DERBY-1489:
----------------------------------------

The issue with views which are dependent on the column being dropped seems to involve
the handling of the prepareToInvalidate() and makeInvalid() methods in the
org.apache.derby.iapi.sql.dictionary.ViewDescriptor class.

As a first experiment, I tried adding case statements for DependencyManager.DROP_COLUMN
into both methods:
 in prepareToInvalidate, break
 in makeInvalid, call dropViewWork

This partially fixes the problem: now ALTER TABLE DROP COLUMN drops any view which
is dependent on that column.

However, with this change, the view is dropped regardless of whether I say CASCADE or RESTRICT.

I notice that ViewDescriptor has handling for REVOKE_PRIVILEGE and REVOKE_PRIVILEGE_RESTRICT,
and I wonder: should I create a DependencyManager.DROP_COLUMN_RESTRICT and mimic
the handling of REVOKE_PRIVILEGE?


> Provide ALTER TABLE DROP COLUMN functionality
> ---------------------------------------------
>
>                 Key: DERBY-1489
>                 URL: http://issues.apache.org/jira/browse/DERBY-1489
>             Project: Derby
>          Issue Type: New Feature
>          Components: Documentation, SQL
>    Affects Versions: 10.0.2.0, 10.0.2.1, 10.1.1.0, 10.2.1.0, 10.1.2.1, 10.1.3.0, 10.1.3.1
>            Reporter: Bryan Pendleton
>         Assigned To: Bryan Pendleton
>         Attachments: dropColumn_2.diff
>
>
> Provide a way to drop a column from an existing table. Possible syntax would be:
>   ALTER TABLE tablename DROP COLUMN columnname CASCADE / RESTRICT;
> Feature should properly handle columns which are used in constraints, views, triggers,
indexes, etc.

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