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Date: Mon, 1 Mar 2010 11:16:05 +0000 (UTC)
From: "Knut Anders Hatlen (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
Subject: [jira] Commented: (DERBY-4538) If the CREATE TRIGGER does not have
 the REFERENCING clause, then there is no need to keep before and after
 values for the triggering table
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    [ https://issues.apache.org/jira/browse/DERBY-4538?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12839645#action_12839645 ] 

Knut Anders Hatlen commented on DERBY-4538:
-------------------------------------------

v2 looks like a good incremental improvement. +1 to commit.

(Nit: The declarations of needToIncludeAllColumns end with two semi-colons.)

> If the CREATE TRIGGER does not have the REFERENCING clause, then there is no need to keep before and after values for the triggering table
> ------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: DERBY-4538
>                 URL: https://issues.apache.org/jira/browse/DERBY-4538
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions: 10.6.0.0
>            Reporter: Mamta A. Satoor
>            Assignee: Mamta A. Satoor
>            Priority: Minor
>         Attachments: DERBY4538_NoReferencingClause_diff_v1.txt, DERBY4538_NoReferencingClause_diff_v2.txt, DERBY4538_NoReferencingClause_stat_v1.txt, DERBY4538_NoReferencingClause_stat_v2.txt
>
>
> In order for the trigger action to have access to before and after values of the triggering table, the CREATE TRIGGER should use the REFERENCING clause. Without the REFERENCING clause, old and new values of triggering table can't be accessed by the trigger action. Based on this, we can improve Derby memory utilization by not keeping old and new values if REFERENCING clause is missing. It will be good to see if the code already does this optimization and if not, then introducing this optimization will definitely be very useful when the triggering table could have LOB columns.

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