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.

1 files changed, 34 insertions, 1 deletions

diff --git a/sql/sql_trigger.h b/sql/sql_trigger.h
index f6754a75284..c077d9567f8 100644
--- a/sql/sql_trigger.h
+++ b/sql/sql_trigger.h
@@ -62,6 +62,27 @@ class Table_triggers_list: public Sql_alloc
   */
   GRANT_INFO        subject_table_grants[TRG_EVENT_MAX][TRG_ACTION_MAX];
 
+  /**
+     This flag indicates that one of the triggers was not parsed successfully,
+     and as a precaution the object has entered a state where all trigger
+     access results in errors until all such triggers are dropped. It is not
+     safe to add triggers since we don't know if the broken trigger has the
+     same name or event type. Nor is it safe to invoke any trigger for the
+     aforementioned reasons. The only safe operations are drop_trigger and
+     drop_all_triggers.
+
+     @see Table_triggers_list::set_parse_error
+   */
+  bool m_has_unparseable_trigger;
+
+  /**
+    This error will be displayed when the user tries to manipulate or invoke
+    triggers on a table that has broken triggers. It will get set only once
+    per statement and thus will contain the first parse error encountered in
+    the trigger file.
+   */
+  char m_parse_error_message[MYSQL_ERRMSG_SIZE];
+
 public:
   /**
     Field responsible for storing triggers definitions in file.
@@ -84,7 +105,7 @@ public:
   /* End of character ser context. */
 
   Table_triggers_list(TABLE *table_arg):
-    record1_field(0), trigger_table(table_arg)
+  record1_field(0), trigger_table(table_arg), m_has_unparseable_trigger(false)
   {
     bzero((char *)bodies, sizeof(bodies));
     bzero((char *)trigger_fields, sizeof(trigger_fields));
@@ -140,6 +161,8 @@ public:
 
   void mark_fields_used(trg_event_type event);
 
+  void set_parse_error_message(char *error_message);
+
   friend class Item_trigger_field;
   friend int sp_cache_routines_and_add_tables_for_triggers(THD *thd, LEX *lex,
                                                             TABLE_LIST *table);
@@ -155,6 +178,16 @@ private:
                                      const char *new_db_name,
                                      LEX_STRING *old_table_name,
                                      LEX_STRING *new_table_name);
+
+  bool check_for_broken_triggers() 
+  {
+    if (m_has_unparseable_trigger)
+    {
+      my_message(ER_PARSE_ERROR, m_parse_error_message, MYF(0));
+      return true;
+    }
+    return false;
+  }
 };
 
 extern const LEX_STRING trg_action_time_type_names[];