1 files changed, 96 insertions, 44 deletions

diff --git a/sql/sql_trigger.cc b/sql/sql_trigger.cc
index 49edf1a7d8b..8ca72eab8bf 100644
--- a/sql/sql_trigger.cc
+++ b/sql/sql_trigger.cc
@@ -107,7 +107,9 @@ const LEX_STRING trg_event_type_names[]=
 };
 
 
-static TABLE_LIST *add_table_for_trigger(THD *thd, sp_name *trig);
+static int
+add_table_for_trigger(THD *thd, sp_name *trig, bool if_exists,
+                      TABLE_LIST ** table);
 
 class Handle_old_incorrect_sql_modes_hook: public Unknown_key_hook
 {
@@ -156,6 +158,13 @@ private:
 */
 bool mysql_create_or_drop_trigger(THD *thd, TABLE_LIST *tables, bool create)
 {
+  /*
+    FIXME: The code below takes too many different paths depending on the
+    'create' flag, so that the justification for a single function
+    'mysql_create_or_drop_trigger', compared to two separate functions
+    'mysql_create_trigger' and 'mysql_drop_trigger' is not apparent.
+    This is a good candidate for a minor refactoring.
+  */
   TABLE *table;
   bool result= TRUE;
   String stmt_query;
@@ -181,10 +190,6 @@ bool mysql_create_or_drop_trigger(THD *thd, TABLE_LIST *tables, bool create)
     DBUG_RETURN(TRUE);
   }
 
-  if (!create &&
-      !(tables= add_table_for_trigger(thd, thd->lex->spname)))
-    DBUG_RETURN(TRUE);
-
   /*
     We don't allow creating triggers on tables in the 'mysql' schema
   */
@@ -194,30 +199,13 @@ bool mysql_create_or_drop_trigger(THD *thd, TABLE_LIST *tables, bool create)
     DBUG_RETURN(TRUE);
   }
 
-  /* We should have only one table in table list. */
-  DBUG_ASSERT(tables->next_global == 0);
-
-  /*
-    Check that the user has TRIGGER privilege on the subject table.
-  */
-  {
-    bool err_status;
-    TABLE_LIST **save_query_tables_own_last= thd->lex->query_tables_own_last;
-    thd->lex->query_tables_own_last= 0;
-
-    err_status= check_table_access(thd, TRIGGER_ACL, tables, 0);
-
-    thd->lex->query_tables_own_last= save_query_tables_own_last;
-
-    if (err_status)
-      DBUG_RETURN(TRUE);
-  }
-
   /*
     There is no DETERMINISTIC clause for triggers, so can't check it.
     But a trigger can in theory be used to do nasty things (if it supported
-    DROP for example) so we do the check for privileges. Triggers have the
-    same nature as functions regarding binlogging: their body is implicitely
+    DROP for example) so we do the check for privileges. For now there is
+    already a stronger test right above; but when this stronger test will
+    be removed, the test below will hold. Because triggers have the same
+    nature as functions regarding binlogging: their body is implicitly
     binlogged, so they share the same danger, so trust_function_creators
     applies to them too.
   */
@@ -228,24 +216,68 @@ bool mysql_create_or_drop_trigger(THD *thd, TABLE_LIST *tables, bool create)
     DBUG_RETURN(TRUE);
   }
 
-  /* We do not allow creation of triggers on temporary tables. */
-  if (create && find_temporary_table(thd, tables))
-  {
-    my_error(ER_TRG_ON_VIEW_OR_TEMP_TABLE, MYF(0), tables->alias);
-    DBUG_RETURN(TRUE);
-  }
-
   /*
     We don't want perform our operations while global read lock is held
-    so we have to wait until its end and then prevent it from occuring
+    so we have to wait until its end and then prevent it from occurring
     again until we are done. (Acquiring LOCK_open is not enough because
-    global read lock is held without helding LOCK_open).
+    global read lock is held without holding LOCK_open).
   */
   if (wait_if_global_read_lock(thd, 0, 1))
     DBUG_RETURN(TRUE);
 
   VOID(pthread_mutex_lock(&LOCK_open));
 
+  if (!create)
+  {
+    bool if_exists= thd->lex->drop_if_exists;
+
+    if (add_table_for_trigger(thd, thd->lex->spname, if_exists, & tables))
+      goto end;
+
+    if (!tables)
+    {
+      DBUG_ASSERT(if_exists);
+      /*
+        Since the trigger does not exist, there is no associated table,
+        and therefore :
+        - no TRIGGER privileges to check,
+        - no trigger to drop,
+        - no table to lock/modify,
+        so the drop statement is successful.
+      */
+      result= FALSE;
+      /* Still, we need to log the query ... */
+      stmt_query.append(thd->query, thd->query_length);
+      goto end;
+    }
+  }
+
+  /*
+    Check that the user has TRIGGER privilege on the subject table.
+  */
+  {
+    bool err_status;
+    TABLE_LIST **save_query_tables_own_last= thd->lex->query_tables_own_last;
+    thd->lex->query_tables_own_last= 0;
+
+    err_status= check_table_access(thd, TRIGGER_ACL, tables, 0);
+
+    thd->lex->query_tables_own_last= save_query_tables_own_last;
+
+    if (err_status)
+      goto end;
+  }
+
+  /* We should have only one table in table list. */
+  DBUG_ASSERT(tables->next_global == 0);
+
+  /* We do not allow creation of triggers on temporary tables. */
+  if (create && find_temporary_table(thd, tables->db, tables->table_name))
+  {
+    my_error(ER_TRG_ON_VIEW_OR_TEMP_TABLE, MYF(0), tables->alias);
+    goto end;
+  }
+
   if (lock_table_names(thd, tables))
     goto end;
 
@@ -1141,13 +1173,17 @@ bool Table_triggers_list::get_trigger_info(THD *thd, trg_event_type event,
     mysql_table_for_trigger()
       thd    - current thread context
       trig   - identifier for trigger
+      if_exists - treat a not existing trigger as a warning if TRUE
+      table - pointer to TABLE_LIST object for the table trigger (output)
 
   RETURN VALUE
-    0 - error
-    # - pointer to TABLE_LIST object for the table
+    0 Success
+    1 Error
 */
 
-static TABLE_LIST *add_table_for_trigger(THD *thd, sp_name *trig)
+static int
+add_table_for_trigger(THD *thd, sp_name *trig, bool if_exists,
+                      TABLE_LIST **table)
 {
   LEX *lex= thd->lex;
   char path_buff[FN_REFLEN];
@@ -1158,6 +1194,7 @@ static TABLE_LIST *add_table_for_trigger(THD *thd, sp_name *trig)
                                           path_buff, &trigname.trigger_table);
   
   DBUG_ENTER("add_table_for_trigger");
+  DBUG_ASSERT(table != NULL);
 
   path.length= build_table_filename(path_buff, FN_REFLEN-1,
                                     trig->m_db.str, trig->m_name.str,
@@ -1166,30 +1203,45 @@ static TABLE_LIST *add_table_for_trigger(THD *thd, sp_name *trig)
 
   if (access(path_buff, F_OK))
   {
+    if (if_exists)
+    {
+      push_warning_printf(thd,
+                         MYSQL_ERROR::WARN_LEVEL_NOTE,
+                         ER_TRG_DOES_NOT_EXIST,
+                         ER(ER_TRG_DOES_NOT_EXIST));
+      *table= NULL;
+      DBUG_RETURN(0);
+    }
+
     my_error(ER_TRG_DOES_NOT_EXIST, MYF(0));
-    DBUG_RETURN(0);
+    DBUG_RETURN(1);
   }
 
   if (!(parser= sql_parse_prepare(&path, thd->mem_root, 1)))
-    DBUG_RETURN(0);
+    DBUG_RETURN(1);
 
   if (!is_equal(&trigname_file_type, parser->type()))
   {
     my_error(ER_WRONG_OBJECT, MYF(0), trig->m_name.str, trigname_file_ext+1,
              "TRIGGERNAME");
-    DBUG_RETURN(0);
+    DBUG_RETURN(1);
   }
 
   if (parser->parse((gptr)&trigname, thd->mem_root,
                     trigname_file_parameters, 1,
                     &trigger_table_hook))
-    DBUG_RETURN(0);
+    DBUG_RETURN(1);
 
   /* We need to reset statement table list to be PS/SP friendly. */
   lex->query_tables= 0;
   lex->query_tables_last= &lex->query_tables;
-  DBUG_RETURN(sp_add_to_query_tables(thd, lex, trig->m_db.str,
-                                     trigname.trigger_table.str, TL_IGNORE));
+  *table= sp_add_to_query_tables(thd, lex, trig->m_db.str,
+                                 trigname.trigger_table.str, TL_IGNORE);
+
+  if (! *table)
+    DBUG_RETURN(1);
+
+  DBUG_RETURN(0);
 }