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https://issues.apache.org/jira/browse/DERBY-5121?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13007356#comment-13007356
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Mamta A. Satoor commented on DERBY-5121:
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This patch will disable the selective column reading for row level triggers
which was introduced by DERBY-1482. As a result of this, Derby will be required
to read all the columns from the trigger table. The generated trigger action
sql's columns will refer to the columns using theie actual column positions in
the trigger table. I have disabled the selective colunm reading by simply
assuming in the create trigger code that we are dealing with pre-10.7
database(as if we are in soft upgrade mode from pre-10.7). During the
soft-upgrade mode with 10.7 and higher releases, we do not do column reading
optimization because the system tables in pre-10.7 are not equipped to keep
additional information about trigger action columns.
This code change was done in DataDictionaryImpl.getTriggerActionString and
looks as follows
boolean in10_7_orHigherVersion = false;
In addition to the above change, I also had to catch the column missing error
in this same method. This can happen if ALTER TABLE DROP COLUMN is dropping a
column from the trigger table and that column is getting referenced in the
trigger action sql. This scenario currently in the 10.7 and 10.8 codelines get
caught when we find that the column being dropped is getting used in trigger
action's referenced column list and if so, then we go ahead and drop that
trigger if we are doing alter table drop column cascade or we throw an error
for trigger dependency if the alter table drop column restrict is being
performed. But since with this patch, we do not keep the trigger action's
referenced column list anymore, we can't catch the drop column's dependency in
the trigger action's referenced column list. Because of this, I have to see if
the trigger action column is not found, then I should throw a column not found
exception. The catch of that exception will drop the trigger is we are dealing
with alter table drop column cascade or it will throw a trigger dependency
exception if we are dealing with alter table drop column restrict.
In addition to the above 2 changes, I had to make following change in
TriggerDescriptor.getActionSPS. The if condition used to be
if((!actionSPS.isValid() ||
(actionSPS.getPreparedStatement() == null)) &&
isRow &&
referencedColsInTriggerAction != null)
But now with this patch, we don't maintain the information in list
referencedColsInTriggerAction and because of that, the above if would always be
false. We want to catch triggers that are using REFERENCING clause and because
of this, the new if condition will look as follows
if((!actionSPS.isValid() ||
(actionSPS.getPreparedStatement() == null)) &&
isRow && (referencingOld || referencingNew))
In addition to the above three changes, I have added new test to incorporate
Rick's reproducible case.
I have not changed the comments in the code yet because I hope to work on the
fix that I proposed earlier in the jira. Once I have that fix in, I can go
ahead and change the comments to match that fix.
derbyall and junit suite ran fine with my changes. If no one has any comments,
I can go ahead and checkin this fix Wednesday evening.
> Data corruption when executing an UPDATE trigger
> ------------------------------------------------
>
> Key: DERBY-5121
> URL: https://issues.apache.org/jira/browse/DERBY-5121
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.7.1.1, 10.8.0.0
> Reporter: Rick Hillegas
> Assignee: Mamta A. Satoor
> Labels: derby_triage10_8
> Attachments: DummyProc.java, triggerBug.sql, triggerBug.sql,
> triggeredBug2.sql, triggeredCorruption.sql
>
>
> When executing an UPDATE trigger, the following error is raised. I will
> attach a test case:
> ERROR XCL12: An attempt was made to put a data value of type
> 'org.apache.derby.impl.jdbc.EmbedClob' into a data value of type 'INTEGER'.
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