Fixed bug#11753738 (formely known as bug#45235) - 5.1 DOES NOT SUPPORT 5.0-ONLY
SYNTAX TRIGGERS IN ANY WAY Table with triggers which were using deprecated (5.0-only) syntax became unavailable for any DML and DDL after upgrade to 5.1 version of server. Attempt to execute any statement on such a table resulted in parsing error reported. Since this included DROP TRIGGER and DROP TABLE statements (actually, the latter was allowed but was not functioning properly for such tables) it was impossible to fix the problem without manual operations on .TRG and .TRN files in data directory. The problem was that failure to parse trigger body (due to 5.0-only syntax) when opening trigger file for a table prevented the table from being open. This made all operations on the table impossible (except DROP TABLE which due to peculiarity in its implementation dropped the table but left trigger files around). This patch solves this problem by silencing error which occurs when we parse trigger body during table open. Error message is preserved for the future use and table is marked as having a broken trigger. We also try to analyze parse tree to recover trigger name, which will be needed in order to drop the broken trigger. DML statements which invoke triggers on the table marked as having broken trigger are prohibited and emit saved error message. The same happens for DDL which change triggers except DROP TRIGGER and DROP TABLE which try their best to do what was requested. Table becomes no longer marked as having broken trigger when last such trigger is dropped. mysql-test/r/trigger-compat.result: Add results for test case for bug#45235 mysql-test/t/trigger-compat.test: Add test case for bug#45235. sql/sp_head.cc: Added protection against MEM_ROOT double restoring to sp_head::restore_thd_mem_root() method. Since this method can be sometimes called twice during parsing of stored routine (the first time during normal flow of parsing, and the second time when a syntax error is detected) we need to shortcut execution of the method to avoid damaging MEM_ROOT by the second consecutive call to this method. sql/sql_trigger.cc: Added error handler Deprecated_trigger_syntax_handler to catch non-OOM errors during parsing of trigger body. Added handling of parse errors into method Table_triggers_list::check_n_load(). sql/sql_trigger.h: Added new members to handle broken triggers and error messages.
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