Backport of Bug#36649 to mysql-next-mr
------------------------------------------------------------ revno: 2630.39.3 revision-id: davi.arnaut@sun.com-20081210215359-i876m4zgc2d6rzs3 parent: kostja@sun.com-20081208222938-9es7wl61moli71ht committer: Davi Arnaut <Davi.Arnaut@Sun.COM> branch nick: 36649-6.0 timestamp: Wed 2008-12-10 19:53:59 -0200 message: Bug#36649: Condition area is not properly cleaned up after stored routine invocation The problem is that the diagnostics area of a trigger is not isolated from the area of the statement that caused the trigger invocation. In MySQL terms, it means that warnings generated during the execution of the trigger are not removed from the "warning area" at the end of the execution. Before this fix, the rules for MySQL message list life cycle (see manual entry for SHOW WARNINGS) did not apply to statements inside stored programs: - The manual says that the list of messages is cleared by a statement that uses a table (any table). However, such statement, if run inside a stored program did not clear the message list. - The manual says that the list is cleared by a statement that generates a new error or a warning, but this was not the case with stored program statements either and is changed to be the case as well. In other words, after this fix, a statement has the same effect on the message list regardless of whether it's executed inside a stored program/sub-statement or not. This introduces an incompatible change: - before this fix, a, e.g. statement inside a trigger could never clear the global warning list - after this fix, a trigger that generates a warning or uses a table, clears the global warning list - however, when we leave a trigger or a function, the caller's warning information is restored (see more on this below). This change is not backward compatible as it is intended to make MySQL behavior similar to the SQL standard behavior: A stored function or trigger will get its own "warning area" (or, in standard terminology, diagnostics area). At the beginning of the stored function or trigger, all messages from the caller area will be copied to the area of the trigger. During execution, the message list will be cleared according to the MySQL rules described on the manual (SHOW WARNINGS entry). At the end of the function/trigger, the "warning area" will be destroyed along with all warnings it contains, except that if the last statement of the function/trigger generated messages, these are copied into the "warning area" of the caller. Consequently, statements that use a table or generate a warning *will* clear warnings inside the trigger, but that will have no effect to the warning list of the calling (outer) statement.
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