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https://issues.apache.org/jira/browse/DERBY-4988?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Mamta A. Satoor updated DERBY-4988:
-----------------------------------
Fix Version/s: 10.8.0.0
Committed the changes to trunk with following commit comments
DERBY-4988 ALTER TABLE DROP COLUMN should make use of information in
SYSTRIGGERS to detect column used through REFERENCING clause to find trigger
dependencies
Derby at the time of ALTER TABLE DROP COLUMN looks for trigger dependencies by
looking for column being dropped in trigger column list but that is not enough.
SQL standard requires that column should not be part of explicit trigger column
list or a triggered action column set.
starting Derby 10.7, we have started keeping track of trigger action columns
which are referenced through the REFERENCING clause. This commit will make use
of that additional info to make a step forward towards meeting the SQL
standards. It still does not recognize the trigger action columns that are not
part of REFERENCING clause. That work can go separately.
I have added upgrade test to make sure that the compatibility does not break
between Derby releases prior to 10.7 and forward.
> ALTER TABLE DROP COLUMN should make use of information in SYSTRIGGERS to
> detect column used through REFERENCING clause to find trigger dependencies
> ---------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: DERBY-4988
> URL: https://issues.apache.org/jira/browse/DERBY-4988
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.7.1.1
> Reporter: Mamta A. Satoor
> Assignee: Mamta A. Satoor
> Fix For: 10.8.0.0
>
>
> At the time of ALTER TABLE DROP COLUMN, Derby checks if the column being
> dropped in a trigger column and if so, then it will not drop the column if it
> is being done in RESTRICT mode or it will drop the trigger while dropping the
> column in CASCADE mode. This does not implement SQL standard to it's
> entirety.
> **************************************
> SQL standard says following about ALTER TABLE DROP COLUMN RESTRICT and
> trigger dependency in CREATE TRIGGER section
> If RESTRICT is specified, then C shall not be referenced in any of the
> following
> d) Either an explicit trigger column list or a triggered action column set of
> any trigger descriptor.
> (The triggered action column set included in the trigger descriptor is the
> set of all distinct, fully qualified names of columns contained in the
> <triggered action>.)
> **************************************
> What is missing from Derby implementation from SQL standard point of view is
> detected triggered action column set.
> Starting 10.7(with DERBY-1482), Derby started keeping track of trigger action
> columns which are referenced through REFERENCING clause. This information can
> be used to improve the behavior of ALTER TABLE DROP COLUMN in 10.7 and
> higher. This will not cover all the trigger action columns since columns
> referenced without the REFERENCING clause are not tracked anywhere at this
> point. More work will need to be done to implement SQL standard completely.
> But we can take a step forward by using the information available in 10.7 and
> higher to detect trigger action columns which are referenced through
> REFERENCING clause
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