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http://issues.apache.org/jira/browse/DERBY-551?page=comments#action_12419777 ]
Daniel John Debrunner commented on DERBY-551:
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I think there are a couple of issues with the approach to checking for
procedures that modify data in a before trigger.
1) The field modifiesSqlData is parser wide, not specific to a single routine.
This may cause issues when the call statement is like:
CALL MYPROC(MYFUNC(), MYOTHERFUNC(2));
This may work, but may be making false assumptions about the ordering of
evaluating nodes.
Also I don't see the field being reset at any time.
2) There is an existing mechanism for checking which routines are allowed, I
would have expected this code to use the same functionality.
After looking into it, I see that it is a runtime check, not a compile time
check.
The existing runtime check is to support the fact that SQL statements executed
in a Java method are not known when the routine is created (in SQL) since they
are executed using dynamic JDBC. So if a routine is declared as READS SQL DATA
then when it is executed by Derby its level of 'SQL allowed' is set in the
statement context . Then any JDBC statements executed by the Java method are
checked against the current level. This includes routines, so a procedure that
is declared READS SQL DATA will throw an exception at runtime if its Java
method attempts to prepare an INSERT SQL statement, or a CALL statement that
executes another SQL procedure that is declared MODIFIES SQL DATA.
See StatementContext.setSQLAllowed(short, boolean);
So we could use the existing mechanism, which means a before trigger with a
CALL procedure that is declared MODIFIES SQL DATA statement would succeed but
would fail at runtime when fired.
> Allow invoking java stored procedures from inside a trigger. Make CALL a
> valid statement in the trigger body.
> -------------------------------------------------------------------------------------------------------------
>
> Key: DERBY-551
> URL: http://issues.apache.org/jira/browse/DERBY-551
> Project: Derby
> Type: New Feature
> Components: SQL
> Versions: 10.1.1.0
> Environment: All platforms
> Reporter: Satheesh Bandaram
> Assignee: Deepa Remesh
> Fix For: 10.2.0.0
> Attachments: ProcedureInTrigger_Tests_v1.html, derby-551-draft1.diff,
> derby-551-draft1.status
>
> Derby currently doesn't allow CALL statement to be used in a trigger body. It
> would be great to allow java stored procedure invocation inside a trigger.
> Since Derby doesn't have SQL procedure language, triggers can only execute a
> single SQL statement. If we allow stored procedures in triggers, it would be
> possible to write a trigger that involves more than just one SQL statement.
> Functions are currently allowed, but they are read-only.
> I believe it is fairly easy to support this enhancement. Need good amount of
> testing though.
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