Bug #21392: multi-table delete with alias table name fails with

            1003: Incorrect table name
in multi-table DELETE the set of tables to delete from actually 
references then tables in the other list, e.g:
DELETE alias_of_t1 FROM t1 alias_of_t1 WHERE ....
is a valid statement.
So we must turn off table name syntactical validity check for alias_of_t1 
because it's not a table name (even if it looks like one).
In order to do that we add a special flag (TL_OPTION_ALIAS) to 
disable the name checking for the aliases in multi-table DELETE.

mysql-test/r/delete.result

@@ -172,3 +172,7 @@ a
 0
 2
 DROP TABLE t1;
+create table t1 (a int);
+delete `4.t1` from t1 as `4.t1` where `4.t1`.a = 5;
+delete FROM `4.t1` USING t1 as `4.t1` where `4.t1`.a = 5;
+drop table t1;

mysql-test/t/delete.test

@@ -153,4 +153,14 @@ DELETE FROM t1 WHERE t1.a > 0 ORDER BY t1.a LIMIT 1;
 SELECT * FROM t1;
 DROP TABLE t1;
 
+#
+# Bug #21392: multi-table delete with alias table name fails with 
+# 1003: Incorrect table name
+#
+
+create table t1 (a int);
+delete `4.t1` from t1 as `4.t1` where `4.t1`.a = 5;
+delete FROM `4.t1` USING t1 as `4.t1` where `4.t1`.a = 5;
+drop table t1;
+
 # End of 4.1 tests

sql/mysql_priv.h

@@ -305,6 +305,7 @@ void debug_sync_point(const char* lock_name, uint lock_timeout);
 #define TL_OPTION_UPDATING	1
 #define TL_OPTION_FORCE_INDEX	2
 #define TL_OPTION_IGNORE_LEAVES 4
+#define TL_OPTION_ALIAS         8
 
 /* Some portable defines */
 

sql/sql_parse.cc

@@ -4863,6 +4863,7 @@ bool add_to_list(THD *thd, SQL_LIST &list,Item *item,bool asc)
     table_options	A set of the following bits:
 			TL_OPTION_UPDATING	Table will be updated
 			TL_OPTION_FORCE_INDEX	Force usage of index
+			TL_OPTION_ALIAS	        an alias in multi table DELETE
     lock_type		How table should be locked
     use_index		List of indexed used in USE INDEX
     ignore_index	List of indexed used in IGNORE INDEX
@@ -4888,7 +4889,8 @@ TABLE_LIST *st_select_lex::add_table_to_list(THD *thd,
   if (!table)
     DBUG_RETURN(0);				// End of memory
   alias_str= alias ? alias->str : table->table.str;
-  if (check_table_name(table->table.str,table->table.length) ||
+  if (!test(table_options & TL_OPTION_ALIAS) &&
+       check_table_name(table->table.str,table->table.length) ||
       table->db.str && check_db_name(table->db.str))
   {
     net_printf(thd, ER_WRONG_TABLE_NAME, table->table.str);

sql/sql_yacc.yy

@@ -4345,14 +4345,17 @@ table_wild_one:
 	ident opt_wild opt_table_alias
 	{
 	  if (!Select->add_table_to_list(YYTHD, new Table_ident($1), $3,
-					 TL_OPTION_UPDATING, Lex->lock_option))
+					 TL_OPTION_UPDATING | 
+                                         TL_OPTION_ALIAS, Lex->lock_option))
 	    YYABORT;
         }
 	| ident '.' ident opt_wild opt_table_alias
 	  {
 	    if (!Select->add_table_to_list(YYTHD,
 					   new Table_ident(YYTHD, $1, $3, 0),
-					   $5, TL_OPTION_UPDATING,
+					   $5, 
+                                           TL_OPTION_UPDATING | 
+                                           TL_OPTION_ALIAS,
 					   Lex->lock_option))
 	      YYABORT;
 	  }