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https://issues.apache.org/jira/browse/DERBY-5294?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13057968#comment-13057968
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Kristian Waagan commented on DERBY-5294:
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I'm not sure we have consensus yet. This far I see the following suggestions on
the table:
a) do work in compress
b) do work in upgrade, requires getting access to the lcc (connecting)
c) add a specific system procedure
d) manual drop/create triggers
My reason for suggesting c) was the same reason that Mike used to justify
adding the trigger recreation to compress table - it's heavy weight. Given that
d) would work for users who find compress table too heavy weight, I'm fine with
scrapping option c) (it does add more code to maintain, and it probably won't
be used much).
That leaves option a) and b), and without having studied this in detail, I lean
towards b) because it seems like the natural place to do it. It would be
interesting to see how much work is required to get that working.
If b) turns out to be too much work, or is otherwise infeasible, we can always
return to to option a) - we already have the code outlined (thanks Mamta). In
that case I'd make sure we update the documentation such that users know what
happens when they run compress table, and maybe make it even clearer how
running compress table affects a running system.
As a side note, are there any drawbacks/risks to "fixing triggers"
unconditionally in compress table?
> 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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