[
http://issues.apache.org/jira/browse/DERBY-1652?page=comments#action_12430906 ]
Yip Ng commented on DERBY-1652:
-------------------------------
Here is the release note for this jira:
Release Note for DERBY-1652
-------------------------------------------
PROBLEM
In some cases, an after update trigger does not get fired upon itself when
its trigger action contains
an update statement on the trigger's subject table.
SYMPTOMS
(1) When defining a trigger for the first time for a table, e.g.:
CREATE TABLE "TEST" ("TESTID" INTEGER NOT NULL GENERATED ALWAYS AS
IDENTITY (START WITH 1, INCREMENT BY 1),
"INFO" INTEGER NOT NULL,
"TIMESTAMP" TIMESTAMP NOT NULL DEFAULT
'1980-01-01-00.00.00.000000');
CREATE TRIGGER UPDATE_TEST
AFTER UPDATE ON TEST
REFERENCING OLD AS OLD
FOR EACH ROW MODE DB2SQL
UPDATE TEST SET TIMESTAMP = CURRENT_TIMESTAMP WHERE TESTID =
OLD.TESTID;
INSERT INTO TEST (INFO) VALUES (1), (2), (3);
UPDATE TEST SET INFO = 1 WHERE TESTID = 2;
The above update statement executes successfully which it is incorrect.
The system should have issued
SQLSTATE 54038 since it self-triggers to its maximum depth of 16.
(2) With the above example, when an user upgrades to a higher version and
issues the same update statement:
UPDATE TEST SET INFO = 1 WHERE TESTID = 2;
ERROR 54038: Maximum depth of nested triggers was exceeded.
The SQLSTATE 54038 is issued in this case because after database
upgrade, the trigger action will be
invalidated by the system and will force a recompilation of the trigger
when it is fired. The system
generates the correct execution plan this time and since the trigger
behavior have changed, this might
cause applications to break unexpectedly.
CAUSE
Derby's did not generate the correct execution plan for self-trigger
invocation when such a trigger is declared
for the first time on the subject table; hence, resulting in the stated
problem above. The affected version is
Derby 10.0 and 10.1.
SOLUTION
A fix to resolve the above Derby symptom is available in 10.1 and 10.2.
WORKAROUND
If self-trigger invocation was not intended by the application, the
application can select which column(s) on the
update statement can cause the trigger to fire in the cREATE TRIGGER
statement. i.e.:
CREATE TRIGGER update_test
AFTER UPDATE OF INFO ON test
REFERENCING OLD AS old
FOR EACH ROW MODE DB2SQL
UPDATE test SET timestamp=current_timestamp WHERE testid=old.testid;
In the above statement, the trigger will only fire when an update is made to
the "info" column instead of any column(s).
> Update trigger updating the same rows as the original update does not throw
> an exception ERROR 54038: "Maximum depth of nested triggers was exceeded" as
> it should
> -------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: DERBY-1652
> URL: http://issues.apache.org/jira/browse/DERBY-1652
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.0.2.0, 10.2.1.0, 10.1.3.1
> Reporter: Kathey Marsden
> Assigned To: Yip Ng
> Fix For: 10.2.1.0, 10.1.3.2
>
> Attachments: derby1652-10.1.3-diff.txt, derby1652-10.1.3-stat.txt,
> derby1652-trunk-diff01.txt, derby1652-trunk-stat01.txt
>
>
> Execution of an update trigger that updates the same row as the original
> update will recurse forever and exceed the maximum nesting level of 16 so
> should throw the exception:
> ERROR 54038: "Maximum depth of nested triggers was exceeded"
> However, it does not always throw the exception. For example:
> CREATE TABLE "TEST" (
>
> "TESTID" INTEGER NOT NULL GENERATED ALWAYS AS IDENTITY (START
> WITH 1,
> INCREMENT BY 1),
>
> "INFO" INTEGER NOT NULL,
>
> "TIMESTAMP" TIMESTAMP NOT NULL DEFAULT
> '1980-01-01-00.00.00.000000'
> );
>
> CREATE TRIGGER UPDATE_TEST
> AFTER UPDATE ON TEST
> REFERENCING OLD AS OLD
> FOR EACH ROW MODE DB2SQL
> UPDATE TEST SET TIMESTAMP = CURRENT_TIMESTAMP WHERE
> TESTID = OLD.TESTID;
> INSERT INTO TEST (INFO) VALUES
> (1),
> (2),
> (3);
> UPDATE TEST SET INFO = 1 WHERE TESTID = 2;
> Does not throw an exception:
> However, If the derby jars are updated to a new version, the correct
> exception is thrown.
> Replace derby jars with new version
> Execute the following in ij:
> UPDATE TEST SET INFO = 1 WHERE TESTID = 2;
> ERROR 54038: Maximum depth of nested triggers was exceeded.
> Note: This issue stemmed from the Invalid issue, DERBY-1603, because a user
> hit the exception after upgrade and thought the exception after upgrade, not
> the lack of exception before upgrade was the problem. This may be a common
> user error, so we need a release note to help mitigate the issue. I will
> add one shortly after confirming the correct trigger syntax.
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