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https://issues.apache.org/jira/browse/DERBY-5294?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13057688#comment-13057688
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Knut Anders Hatlen commented on DERBY-5294:
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I'm not sure changing compress table this way is worth the extra complexity.
The extra work done by compress table isn't something that's generally useful
during compression, is it? And there still is a manual step needed to get old
databases to pick up the fix for DERBY-1482. Whether that extra step is
dropping/recreating the trigger or compressing the table doesn't make much
difference, so the reduced code complexity by sticking to the drop/recreate
approach sounds more attractive to me. Even if dropping/recreating the trigger
means a little more typing in ij for those who need the workaround, I'd prefer
to let them take that extra burden as a one-time job, rather than us having to
maintain a complex piece of code for all future releases.
> Enhance compress table to drop and recreate the triggers. This will enable
> pre-10.9 triggers (after hard upgrade to 10.9) to read only the required
> columns from the trigger table.
> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: DERBY-5294
> URL: https://issues.apache.org/jira/browse/DERBY-5294
> Project: Derby
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 10.9.0.0
> Reporter: Mamta A. Satoor
> Attachments: DERBY5289_alltriggers_06282011_diff.txt,
> DERBY5289_alltriggers_06282011_stat.txt
>
>
> Triggers created prior to 10.9 release will continue to read all the columns
> from trigger table even after database has been upgraded to 10.9 and higher.
> Which in another words means that such triggers will not benefit from work
> done for DERBY-1482.
> With DERBY-1482 (which went in 10.9 codeline), triggers will read only the
> columns needed by the triggering sql and firing triggers. But this applies
> only to triggers created in 10.9 and higher. Any triggers created prior to
> 10.9 will not be able to take advantage of DERBY-1482 because those triggers
> do not keep the information about the trigger action columns. Currently, the
> users will have to drop and recreate the triggers which use the REFERENCING
> CLAUSE and were created prior to 10.9 to take advantage of DERBY-1482.
> The alternative to manual drop and recreate of such triggers can be explored
> as part of this jira. Couple options are
> 1)UPDATE sql should detect that the trigger does not have information about
> the trigger action columns and hence it should make the trigger collect that
> information.
> 2)At the time of upgrade, when we mark all the SPSes invalid, detect the
> triggers which do not have the information about the trigger action columns
> and make those triggers collect that information.
> 3)Enhance ALTER TABLE COMPRESS to detect the triggers which do not have the
> information about the trigger action columns and make those triggers collect
> that information. With this option, users will still have to manually do
> ALTER TABLE COMPRESS to fix the triggers but atleast they won't have to get
> the original trigger definitions and drop and recreate the triggers using
> those original trigger definitions.
> 10.9 currently does not have central place where the trigger will go and
> collect the information about trigger action columns. We do have code in
> ALTER TABLE DROP COLUMN to collect the trigger action column info but it will
> probably better to have such a code in TriggerDescriptor so it can be used by
> the approach taken to fix this jira.
> Note that without the fix for this jira, the triggers created prior to 10.9
> will work just fine after upgrade to 10.9 and higher but they will not be
> able to prevent reading of columns that are not necessary for the triggering
> sql and firing triggers
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