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.

mysql-test/r/trigger-compat.result

@@ -43,3 +43,101 @@ DROP TABLE t2;
 DROP USER mysqltest_dfn@localhost;
 DROP USER mysqltest_inv@localhost;
 DROP DATABASE mysqltest_db1;
+USE test;
+#
+# Bug#45235: 5.1 does not support 5.0-only syntax triggers in any way
+#
+DROP TABLE IF EXISTS t1, t2, t3;
+CREATE TABLE t1 ( a INT );
+CREATE TABLE t2 ( a INT );
+CREATE TABLE t3 ( a INT );
+INSERT INTO t1 VALUES (1), (2), (3);
+INSERT INTO t2 VALUES (1), (2), (3);
+INSERT INTO t3 VALUES (1), (2), (3);
+# We simulate importing a trigger from 5.0 by writing a .TRN file for
+# each trigger plus a .TRG file the way MySQL 5.0 would have done it, 
+# with syntax allowed in 5.0 only.
+#
+# Note that in 5.0 the following lines are missing from t1.TRG:
+#
+# client_cs_names='latin1'
+# connection_cl_names='latin1_swedish_ci'
+# db_cl_names='latin1_swedish_ci'
+# We will get parse errors for most DDL and DML statements when the table
+# has broken triggers. The parse error refers to the first broken 
+# trigger.
+CREATE TRIGGER tr16 AFTER UPDATE ON t1 FOR EACH ROW INSERT INTO t1 VALUES (1);
+ERROR 42000: Trigger 'tr13' has an error in its body: 'You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'a USING t1 a' at line 1'
+CREATE TRIGGER tr22 BEFORE INSERT ON t2 FOR EACH ROW DELETE FROM non_existing_table;
+ERROR 42000: Unknown trigger has an error in its body: 'You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'Not allowed syntax here, and trigger name cant be extracted either.' at line 1'
+SHOW TRIGGERS;
+Trigger	Event	Table	Statement	Timing	Created	sql_mode	Definer	character_set_client	collation_connection	Database Collation
+tr11	INSERT	t1	DELETE FROM t3	BEFORE	NULL		root@localhost	latin1	latin1_swedish_ci	latin1_swedish_ci
+tr12	INSERT	t1	DELETE FROM t3	AFTER	NULL		root@localhost	latin1	latin1_swedish_ci	latin1_swedish_ci
+tr14	DELETE	t1	DELETE FROM non_existing_table	AFTER	NULL		root@localhost	latin1	latin1_swedish_ci	latin1_swedish_ci
+Warnings:
+Warning	1603	Triggers for table `test`.`t1` have no creation context
+Warning	1603	Triggers for table `test`.`t2` have no creation context
+INSERT INTO t1 VALUES (1);
+ERROR 42000: Trigger 'tr13' has an error in its body: 'You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'a USING t1 a' at line 1'
+INSERT INTO t2 VALUES (1);
+ERROR 42000: Unknown trigger has an error in its body: 'You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'Not allowed syntax here, and trigger name cant be extracted either.' at line 1'
+DELETE FROM t1;
+ERROR 42000: Trigger 'tr13' has an error in its body: 'You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'a USING t1 a' at line 1'
+UPDATE t1 SET a = 1 WHERE a = 1;
+ERROR 42000: Trigger 'tr13' has an error in its body: 'You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'a USING t1 a' at line 1'
+SELECT * FROM t1;
+a
+1
+2
+3
+RENAME TABLE t1 TO t1_2;
+ERROR 42000: Trigger 'tr13' has an error in its body: 'You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'a USING t1 a' at line 1'
+SHOW TRIGGERS;
+Trigger	Event	Table	Statement	Timing	Created	sql_mode	Definer	character_set_client	collation_connection	Database Collation
+tr11	INSERT	t1	DELETE FROM t3	BEFORE	NULL		root@localhost	latin1	latin1_swedish_ci	latin1_swedish_ci
+tr12	INSERT	t1	DELETE FROM t3	AFTER	NULL		root@localhost	latin1	latin1_swedish_ci	latin1_swedish_ci
+tr14	DELETE	t1	DELETE FROM non_existing_table	AFTER	NULL		root@localhost	latin1	latin1_swedish_ci	latin1_swedish_ci
+Warnings:
+Warning	1603	Triggers for table `test`.`t1` have no creation context
+DROP TRIGGER tr11;
+Warnings:
+Warning	1603	Triggers for table `test`.`t1` have no creation context
+DROP TRIGGER tr12;
+DROP TRIGGER tr13;
+DROP TRIGGER tr14;
+DROP TRIGGER tr15;
+SHOW TRIGGERS;
+Trigger	Event	Table	Statement	Timing	Created	sql_mode	Definer	character_set_client	collation_connection	Database Collation
+# Make sure there is no trigger file left.
+# We write the same trigger files one more time to test DROP TABLE.
+DROP TABLE t1;
+Warnings:
+Warning	1603	Triggers for table `test`.`t1` have no creation context
+DROP TABLE t2;
+Warnings:
+Warning	1603	Triggers for table `test`.`t2` have no creation context
+DROP TABLE t3;
+# Make sure there is no trigger file left.
+CREATE TABLE t1 ( a INT );
+CREATE TABLE t2 ( a INT );
+INSERT INTO t1 VALUES (1), (2), (3);
+INSERT INTO t2 VALUES (1), (2), (3);
+# We write three trigger files. First trigger is syntaxically incorrect, next trigger is correct
+# and last trigger is broken.
+# Next we try to execute SHOW CREATE TRGGIR command for broken trigger and then try to drop one.
+FLUSH TABLE t1;
+SHOW CREATE TRIGGER tr12;
+Trigger	sql_mode	SQL Original Statement	character_set_client	collation_connection	Database Collation
+tr12		CREATE DEFINER=`root`@`localhost` TRIGGER tr12 BEFORE INSERT ON t1 FOR EACH ROW DELETE FROM t2	latin1	latin1_swedish_ci	latin1_swedish_ci
+Warnings:
+Warning	1603	Triggers for table `test`.`t1` have no creation context
+SHOW CREATE TRIGGER tr11;
+Trigger	sql_mode	SQL Original Statement	character_set_client	collation_connection	Database Collation
+tr11		CREATE DEFINER=`root`@`localhost` TRIGGER tr11 BEFORE DELETE ON t1 FOR EACH ROW DELETE FROM t1 a USING t1 a	latin1	latin1_swedish_ci	latin1_swedish_ci
+DROP TRIGGER tr12;
+Warnings:
+Warning	1603	Triggers for table `test`.`t1` have no creation context
+DROP TRIGGER tr11;
+DROP TABLE t1;
+DROP TABLE t2;

mysql-test/r/trigger.result

@@ -2134,10 +2134,8 @@ CREATE TRIGGER trg1 BEFORE INSERT ON t2 FOR EACH ROW INSERT/*!INTO*/t1 VALUES (1
 # Used to crash
 SHOW TRIGGERS IN db1;
 Trigger	Event	Table	Statement	Timing	Created	sql_mode	Definer	character_set_client	collation_connection	Database Collation
-Warnings:
-Warning	1064	You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'VALUES (1)' at line 1
 INSERT INTO t2 VALUES (1);
-ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'VALUES (1)' at line 1
+ERROR 42000: Trigger 'trg1' has an error in its body: 'You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'VALUES (1)' at line 1'
 SELECT * FROM t1;
 b
 # Work around Bug#45235

mysql-test/t/trigger-compat.test

@@ -106,4 +106,178 @@ DROP TABLE t2;
 DROP USER mysqltest_dfn@localhost;
 DROP USER mysqltest_inv@localhost;
 DROP DATABASE mysqltest_db1;
+USE test;
 
+
+--echo #
+--echo # Bug#45235: 5.1 does not support 5.0-only syntax triggers in any way
+--echo #
+let $MYSQLD_DATADIR=`SELECT @@datadir`;
+
+--disable_warnings
+DROP TABLE IF EXISTS t1, t2, t3;
+--enable_warnings
+
+CREATE TABLE t1 ( a INT );
+CREATE TABLE t2 ( a INT );
+CREATE TABLE t3 ( a INT );
+INSERT INTO t1 VALUES (1), (2), (3);
+INSERT INTO t2 VALUES (1), (2), (3);
+INSERT INTO t3 VALUES (1), (2), (3);
+
+--echo # We simulate importing a trigger from 5.0 by writing a .TRN file for
+--echo # each trigger plus a .TRG file the way MySQL 5.0 would have done it, 
+--echo # with syntax allowed in 5.0 only.
+--echo #
+--echo # Note that in 5.0 the following lines are missing from t1.TRG:
+--echo #
+--echo # client_cs_names='latin1'
+--echo # connection_cl_names='latin1_swedish_ci'
+--echo # db_cl_names='latin1_swedish_ci'
+
+--write_file $MYSQLD_DATADIR/test/tr11.TRN
+TYPE=TRIGGERNAME
+trigger_table=t1
+EOF
+
+--write_file $MYSQLD_DATADIR/test/tr12.TRN
+TYPE=TRIGGERNAME
+trigger_table=t1
+EOF
+
+--write_file $MYSQLD_DATADIR/test/tr13.TRN
+TYPE=TRIGGERNAME
+trigger_table=t1
+EOF
+
+--write_file $MYSQLD_DATADIR/test/tr14.TRN
+TYPE=TRIGGERNAME
+trigger_table=t1
+EOF
+
+--write_file $MYSQLD_DATADIR/test/tr15.TRN
+TYPE=TRIGGERNAME
+trigger_table=t1
+EOF
+
+--write_file $MYSQLD_DATADIR/test/t1.TRG
+TYPE=TRIGGERS
+triggers='CREATE DEFINER=`root`@`localhost` TRIGGER tr11 BEFORE INSERT ON t1 FOR EACH ROW DELETE FROM t3' 'CREATE DEFINER=`root`@`localhost` TRIGGER tr12 AFTER INSERT ON t1 FOR EACH ROW DELETE FROM t3' 'CREATE DEFINER=`root`@`localhost` TRIGGER tr13 BEFORE DELETE ON t1 FOR EACH ROW DELETE FROM t1 a USING t1 a' 'CREATE DEFINER=`root`@`localhost` TRIGGER tr14 AFTER DELETE ON t1 FOR EACH ROW DELETE FROM non_existing_table' 'CREATE DEFINER=`root`@`localhost` TRIGGER tr15 BEFORE UPDATE ON t1 FOR EACH ROW DELETE FROM non_existing_table a USING non_existing_table a'
+sql_modes=0 0 0 0 0
+definers='root@localhost' 'root@localhost' 'root@localhost' 'root@localhost' 'root@localhost'
+EOF
+
+--write_file $MYSQLD_DATADIR/test/t2.TRG
+TYPE=TRIGGERS
+triggers='Not allowed syntax here, and trigger name cant be extracted either.'
+sql_modes=0
+definers='root@localhost'
+EOF
+
+--echo # We will get parse errors for most DDL and DML statements when the table
+--echo # has broken triggers. The parse error refers to the first broken 
+--echo # trigger.
+--error ER_PARSE_ERROR
+CREATE TRIGGER tr16 AFTER UPDATE ON t1 FOR EACH ROW INSERT INTO t1 VALUES (1);
+--error ER_PARSE_ERROR
+CREATE TRIGGER tr22 BEFORE INSERT ON t2 FOR EACH ROW DELETE FROM non_existing_table;
+SHOW TRIGGERS;
+--error ER_PARSE_ERROR
+INSERT INTO t1 VALUES (1);
+--error ER_PARSE_ERROR
+INSERT INTO t2 VALUES (1);
+--error ER_PARSE_ERROR
+DELETE FROM t1;
+--error ER_PARSE_ERROR
+UPDATE t1 SET a = 1 WHERE a = 1;
+SELECT * FROM t1;
+--error ER_PARSE_ERROR
+RENAME TABLE t1 TO t1_2;
+SHOW TRIGGERS;
+
+DROP TRIGGER tr11;
+DROP TRIGGER tr12;
+DROP TRIGGER tr13;
+DROP TRIGGER tr14;
+DROP TRIGGER tr15;
+
+SHOW TRIGGERS;
+
+--echo # Make sure there is no trigger file left.
+--list_files $MYSQLD_DATADIR/test/ tr*
+
+--echo # We write the same trigger files one more time to test DROP TABLE.
+--write_file $MYSQLD_DATADIR/test/tr11.TRN
+TYPE=TRIGGERNAME
+trigger_table=t1
+EOF
+
+--write_file $MYSQLD_DATADIR/test/tr12.TRN
+TYPE=TRIGGERNAME
+trigger_table=t1
+EOF
+
+--write_file $MYSQLD_DATADIR/test/tr13.TRN
+TYPE=TRIGGERNAME
+trigger_table=t1
+EOF
+
+--write_file $MYSQLD_DATADIR/test/tr14.TRN
+TYPE=TRIGGERNAME
+trigger_table=t1
+EOF
+
+--write_file $MYSQLD_DATADIR/test/tr15.TRN
+TYPE=TRIGGERNAME
+trigger_table=t1
+EOF
+
+--write_file $MYSQLD_DATADIR/test/t1.TRG
+TYPE=TRIGGERS
+triggers='CREATE DEFINER=`root`@`localhost` TRIGGER tr11 BEFORE INSERT ON t1 FOR EACH ROW DELETE FROM t3' 'CREATE DEFINER=`root`@`localhost` TRIGGER tr12 AFTER INSERT ON t1 FOR EACH ROW DELETE FROM t3' 'CREATE DEFINER=`root`@`localhost` TRIGGER tr13 BEFORE DELETE ON t1 FOR EACH ROW DELETE FROM t1 a USING t1 a' 'CREATE DEFINER=`root`@`localhost` TRIGGER tr14 AFTER DELETE ON t1 FOR EACH ROW DELETE FROM non_existing_table' 'CREATE DEFINER=`root`@`localhost` TRIGGER tr15 BEFORE UPDATE ON t1 FOR EACH ROW DELETE FROM non_existing_table a USING non_existing_table a'
+sql_modes=0 0 0 0 0
+definers='root@localhost' 'root@localhost' 'root@localhost' 'root@localhost' 'root@localhost'
+EOF
+
+DROP TABLE t1;
+DROP TABLE t2;
+DROP TABLE t3;
+
+--echo # Make sure there is no trigger file left.
+
+--list_files $MYSQLD_DATADIR/test/ tr*
+
+CREATE TABLE t1 ( a INT );
+CREATE TABLE t2 ( a INT );
+INSERT INTO t1 VALUES (1), (2), (3);
+INSERT INTO t2 VALUES (1), (2), (3);
+
+--echo # We write three trigger files. First trigger is syntaxically incorrect, next trigger is correct
+--echo # and last trigger is broken.
+--echo # Next we try to execute SHOW CREATE TRGGIR command for broken trigger and then try to drop one.
+--write_file $MYSQLD_DATADIR/test/tr11.TRN
+TYPE=TRIGGERNAME
+trigger_table=t1
+EOF
+
+--write_file $MYSQLD_DATADIR/test/tr12.TRN
+TYPE=TRIGGERNAME
+trigger_table=t1
+EOF
+
+--write_file $MYSQLD_DATADIR/test/t1.TRG
+TYPE=TRIGGERS
+triggers='CREATE the wrongest trigger_in_the_world' 'CREATE DEFINER=`root`@`localhost` TRIGGER tr11 BEFORE DELETE ON t1 FOR EACH ROW DELETE FROM t1 a USING t1 a' 'CREATE DEFINER=`root`@`localhost` TRIGGER tr12 BEFORE INSERT ON t1 FOR EACH ROW DELETE FROM t2'
+sql_modes=0 0 0
+definers='root@localhost' 'root@localhost' 'root@localhost'
+EOF
+
+FLUSH TABLE t1;
+
+SHOW CREATE TRIGGER tr12;
+SHOW CREATE TRIGGER tr11;
+DROP TRIGGER tr12;
+DROP TRIGGER tr11;
+
+DROP TABLE t1;
+DROP TABLE t2;

sql/sp_head.cc

@@ -2354,6 +2354,21 @@ void
 sp_head::restore_thd_mem_root(THD *thd)
 {
   DBUG_ENTER("sp_head::restore_thd_mem_root");
+
+  /*
+   In some cases our parser detects a syntax error and calls
+   LEX::cleanup_lex_after_parse_error() method only after
+   finishing parsing the whole routine. In such a situation
+   sp_head::restore_thd_mem_root() will be called twice - the
+   first time as part of normal parsing process and the second
+   time by cleanup_lex_after_parse_error().
+   To avoid ruining active arena/mem_root state in this case we
+   skip restoration of old arena/mem_root if this method has been
+   already called for this routine.
+  */
+  if (!m_thd)
+    DBUG_VOID_RETURN;
+
   Item *flist= free_list;	// The old list
   set_query_arena(thd);         // Get new free_list and mem_root
   state= INITIALIZED_FOR_SP;

sql/sql_parse.cc

@@ -7972,10 +7972,14 @@ bool parse_sql(THD *thd,
 
   bool mysql_parse_status= MYSQLparse(thd) != 0;
 
-  /* Check that if MYSQLparse() failed, thd->is_error() is set. */
+  /*
+    Check that if MYSQLparse() failed, thd->is_error() is set (unless
+    we have an error handler installed, which might have silenced error).
+  */
 
   DBUG_ASSERT(!mysql_parse_status ||
-              (mysql_parse_status && thd->is_error()));
+              (mysql_parse_status && thd->is_error()) ||
+              (mysql_parse_status && thd->get_internal_handler()));
 
   /* Reset parser state. */
 

sql/sql_trigger.cc

@@ -19,6 +19,7 @@
 #include "sp_head.h"
 #include "sql_trigger.h"
 #include "parse_file.h"
+#include <mysys_err.h>
 
 /*************************************************************************/
 
@@ -292,6 +293,52 @@ private:
 };
 
 
+/**
+  An error handler that catches all non-OOM errors which can occur during
+  parsing of trigger body. Such errors are ignored and corresponding error
+  message is used to construct a more verbose error message which contains
+  name of problematic trigger. This error message is later emitted when
+  one tries to perform DML or some of DDL on this table.
+  Also, if possible, grabs name of the trigger being parsed so it can be
+  used to correctly drop problematic trigger.
+*/
+class Deprecated_trigger_syntax_handler : public Internal_error_handler 
+{
+private:
+
+  char m_message[MYSQL_ERRMSG_SIZE];
+  LEX_STRING *m_trigger_name;
+
+public:
+
+  Deprecated_trigger_syntax_handler() : m_trigger_name(NULL) {}
+
+  virtual bool handle_error(uint sql_errno, const char *message,
+                            MYSQL_ERROR::enum_warning_level level, THD *thd)
+  {
+    if (sql_errno != EE_OUTOFMEMORY &&
+        sql_errno != ER_OUT_OF_RESOURCES)
+    {
+      if(thd->lex->spname)
+        m_trigger_name= &thd->lex->spname->m_name;
+      if (m_trigger_name)
+        my_snprintf(m_message, sizeof(m_message),
+                    "Trigger '%s' has an error in its body: '%s'",
+                    m_trigger_name->str, message);
+      else
+        my_snprintf(m_message, sizeof(m_message),
+                    "Unknown trigger has an error in its body: '%s'",
+                    message);
+      return true;
+    }
+    return false;
+  }
+
+  LEX_STRING *get_trigger_name() { return m_trigger_name; }
+  char *get_error_message() { return m_message; }
+};
+
+
 /**
   Create or drop trigger for table.
 
@@ -575,6 +622,8 @@ bool Table_triggers_list::create_trigger(THD *thd, TABLE_LIST *tables,
   LEX_STRING *trg_connection_cl_name;
   LEX_STRING *trg_db_cl_name;
 
+  if (check_for_broken_triggers())
+    return true;
 
   /* Trigger must be in the same schema as target table. */
   if (my_strcasecmp(table_alias_charset, table->s->db.str,
@@ -848,7 +897,7 @@ static bool rm_trigger_file(char *path, const char *db,
   @param path         char buffer of size FN_REFLEN to be used
                       for constructing path to .TRN file.
   @param db           trigger's database name
-  @param table_name   trigger's name
+  @param trigger_name trigger's name
 
   @retval
     False   success
@@ -1312,12 +1361,11 @@ bool Table_triggers_list::check_n_load(THD *thd, const char *db,
         lex_start(thd);
         thd->spcont= NULL;
 
-        if (parse_sql(thd, & parser_state, creation_ctx))
-        {
-          /* Currently sphead is always deleted in case of a parse error */
-          DBUG_ASSERT(lex.sphead == 0);
-          goto err_with_lex_cleanup;
-        }
+        Deprecated_trigger_syntax_handler error_handler;
+        thd->push_internal_handler(&error_handler);
+        bool parse_error= parse_sql(thd, & parser_state, creation_ctx);
+        thd->pop_internal_handler();
+
         /*
           Not strictly necessary to invoke this method here, since we know
           that we've parsed CREATE TRIGGER and not an
@@ -1328,6 +1376,52 @@ bool Table_triggers_list::check_n_load(THD *thd, const char *db,
         */
         lex.set_trg_event_type_for_tables();
 
+        if (parse_error)
+        {
+          if (!triggers->m_has_unparseable_trigger)
+            triggers->set_parse_error_message(error_handler.get_error_message());
+          /* Currently sphead is always set to NULL in case of a parse error */
+          DBUG_ASSERT(lex.sphead == 0);
+          if (error_handler.get_trigger_name())
+          {
+            LEX_STRING *trigger_name;
+            const LEX_STRING *orig_trigger_name= error_handler.get_trigger_name();
+
+            if (!(trigger_name= alloc_lex_string(&table->mem_root)) ||
+                !(trigger_name->str= strmake_root(&table->mem_root,
+                                                  orig_trigger_name->str,
+                                                  orig_trigger_name->length)))
+              goto err_with_lex_cleanup;
+
+            trigger_name->length= orig_trigger_name->length;
+
+            if (triggers->names_list.push_back(trigger_name,
+                                               &table->mem_root))
+              goto err_with_lex_cleanup;
+          }
+          else
+          {
+            /* 
+               The Table_triggers_list is not constructed as a list of
+               trigger objects as one would expect, but rather of lists of
+               properties of equal length. Thus, even if we don't get the
+               trigger name, we still fill all in all the lists with
+               placeholders as we might otherwise create a skew in the
+               lists. Obviously, this has to be refactored.
+            */
+            LEX_STRING *empty= alloc_lex_string(&table->mem_root);
+            if (!empty)
+              goto err_with_lex_cleanup;
+
+            empty->str= const_cast<char*>("");
+            empty->length= 0;
+            if (triggers->names_list.push_back(empty, &table->mem_root))
+              goto err_with_lex_cleanup;
+          }
+          lex_end(&lex);
+          continue;
+        }
+
         lex.sphead->set_info(0, 0, &lex.sp_chistics, (ulong) *trg_sql_mode);
 
         int event= lex.trg_chistics.event;
@@ -1394,9 +1488,8 @@ bool Table_triggers_list::check_n_load(THD *thd, const char *db,
         char fname[NAME_LEN + 1];
         DBUG_ASSERT((!my_strcasecmp(table_alias_charset, lex.query_tables->db, db) ||
                      (check_n_cut_mysql50_prefix(db, fname, sizeof(fname)) &&
-                      !my_strcasecmp(table_alias_charset, lex.query_tables->db, fname))) &&
-                    (!my_strcasecmp(table_alias_charset, lex.query_tables->table_name,
-                                    table_name) ||
+                      !my_strcasecmp(table_alias_charset, lex.query_tables->db, fname))));
+        DBUG_ASSERT((!my_strcasecmp(table_alias_charset, lex.query_tables->table_name, table_name) ||
                      (check_n_cut_mysql50_prefix(table_name, fname, sizeof(fname)) &&
                       !my_strcasecmp(table_alias_charset, lex.query_tables->table_name, fname))));
 #endif
@@ -1680,6 +1773,13 @@ bool Table_triggers_list::drop_all_triggers(THD *thd, char *db, char *name)
 
     while ((trigger= it_name++))
     {
+      /*
+        Trigger, which body we failed to parse during call
+        Table_triggers_list::check_n_load(), might be missing name.
+        Such triggers have zero-length name and are skipped here.
+      */
+      if (trigger->length == 0)
+        continue;
       if (rm_trigname_file(path, db, trigger->str))
       {
         /*
@@ -1903,6 +2003,11 @@ bool Table_triggers_list::change_table_name(THD *thd, const char *db,
   }
   if (table.triggers)
   {
+    if (table.triggers->check_for_broken_triggers())
+    {
+      result= 1;
+      goto end;
+    }
     LEX_STRING old_table_name= { (char *) old_table, strlen(old_table) };
     LEX_STRING new_table_name= { (char *) new_table, strlen(new_table) };
     /*
@@ -1991,6 +2096,9 @@ bool Table_triggers_list::process_triggers(THD *thd,
   sp_head *sp_trigger= bodies[event][time_type];
   SELECT_LEX *save_current_select;
 
+  if (check_for_broken_triggers())
+    return true;
+
   if (sp_trigger == NULL)
     return FALSE;
 
@@ -2069,6 +2177,22 @@ void Table_triggers_list::mark_fields_used(trg_event_type event)
 }
 
 
+/**
+   Signals to the Table_triggers_list that a parse error has occured when
+   reading a trigger from file. This makes the Table_triggers_list enter an
+   error state flagged by m_has_unparseable_trigger == true. The error message
+   will be used whenever a statement invoking or manipulating triggers is
+   issued against the Table_triggers_list's table.
+
+   @param error_message The error message thrown by the parser.
+ */
+void Table_triggers_list::set_parse_error_message(char *error_message)
+{
+  m_has_unparseable_trigger= true;
+  strcpy(m_parse_error_message, error_message);
+}
+
+
 /**
   Trigger BUG#14090 compatibility hook.
 

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[];