Bug#30747 Create table with identical constraint names behaves incorrectly

MySQL provides what appears to be a non standard extension to the
FOREIGN KEY syntax which let users name (label/tag) a foreign key
to more easily identify a specific foreign key if any problems show
up later during the query parsing or execution. But the foreign key
name was not being properly set to the right key, possible leaving
the foreign key with no name.

mysql-test/include/mix1.inc

@@ -1096,4 +1096,38 @@ select @b:=f2 from t1;
 select if(@a=@b,"ok","wrong");
 drop table t1;
 
+#
+# Bug#30747 Create table with identical constraint names behaves incorrectly
+#
+
+if ($test_foreign_keys)
+{
+  CREATE TABLE t1 (a INT NOT NULL, b INT NOT NULL, PRIMARY KEY (a,b)) engine=innodb;
+  --error ER_WRONG_FK_DEF
+  CREATE TABLE t2 (c INT NOT NULL, d INT NOT NULL, PRIMARY KEY (c,d),
+                  CONSTRAINT c2 FOREIGN KEY f2 (c) REFERENCES t1 (a,b) ON UPDATE NO ACTION) engine=innodb;
+  --error ER_WRONG_FK_DEF
+  CREATE TABLE t2 (c INT NOT NULL, d INT NOT NULL, PRIMARY KEY (c,d),
+                  CONSTRAINT c2 FOREIGN KEY (c) REFERENCES t1 (a,b) ON UPDATE NO ACTION) engine=innodb;
+  CREATE TABLE t2 (c INT NOT NULL, d INT NOT NULL, PRIMARY KEY (c,d),
+                  CONSTRAINT c1 FOREIGN KEY c2 (c) REFERENCES t1 (a) ON DELETE NO ACTION,
+                  CONSTRAINT c2 FOREIGN KEY (c) REFERENCES t1 (a) ON UPDATE NO ACTION) engine=innodb;
+  ALTER TABLE t2 DROP FOREIGN KEY c2;
+  DROP TABLE t2;
+  --error ER_WRONG_FK_DEF
+  CREATE TABLE t2 (c INT NOT NULL, d INT NOT NULL, PRIMARY KEY (c,d),
+                  FOREIGN KEY (c) REFERENCES t1 (a,k) ON UPDATE NO ACTION) engine=innodb;
+  --error ER_WRONG_FK_DEF
+  CREATE TABLE t2 (c INT NOT NULL, d INT NOT NULL, PRIMARY KEY (c,d),
+                  FOREIGN KEY f1 (c) REFERENCES t1 (a,k) ON UPDATE NO ACTION) engine=innodb;
+  CREATE TABLE t2 (c INT NOT NULL, d INT NOT NULL, PRIMARY KEY (c,d),
+                  CONSTRAINT c1 FOREIGN KEY f1 (c) REFERENCES t1 (a) ON DELETE NO ACTION,
+                  CONSTRAINT c2 FOREIGN KEY (c) REFERENCES t1 (a) ON UPDATE NO ACTION,
+                  FOREIGN KEY f3 (c) REFERENCES t1 (a) ON UPDATE NO ACTION,
+                  FOREIGN KEY (c) REFERENCES t1 (a) ON UPDATE NO ACTION) engine=innodb;
+  SHOW CREATE TABLE t2;
+  DROP TABLE t2;
+  DROP TABLE t1;
+}
+
 --echo End of 5.1 tests

mysql-test/r/innodb_mysql.result

@@ -1273,4 +1273,40 @@ select if(@a=@b,"ok","wrong");
 if(@a=@b,"ok","wrong")
 ok
 drop table t1;
+CREATE TABLE t1 (a INT NOT NULL, b INT NOT NULL, PRIMARY KEY (a,b)) engine=innodb;
+CREATE TABLE t2 (c INT NOT NULL, d INT NOT NULL, PRIMARY KEY (c,d),
+CONSTRAINT c2 FOREIGN KEY f2 (c) REFERENCES t1 (a,b) ON UPDATE NO ACTION) engine=innodb;
+ERROR 42000: Incorrect foreign key definition for 'f2': Key reference and table reference don't match
+CREATE TABLE t2 (c INT NOT NULL, d INT NOT NULL, PRIMARY KEY (c,d),
+CONSTRAINT c2 FOREIGN KEY (c) REFERENCES t1 (a,b) ON UPDATE NO ACTION) engine=innodb;
+ERROR 42000: Incorrect foreign key definition for 'c2': Key reference and table reference don't match
+CREATE TABLE t2 (c INT NOT NULL, d INT NOT NULL, PRIMARY KEY (c,d),
+CONSTRAINT c1 FOREIGN KEY c2 (c) REFERENCES t1 (a) ON DELETE NO ACTION,
+CONSTRAINT c2 FOREIGN KEY (c) REFERENCES t1 (a) ON UPDATE NO ACTION) engine=innodb;
+ALTER TABLE t2 DROP FOREIGN KEY c2;
+DROP TABLE t2;
+CREATE TABLE t2 (c INT NOT NULL, d INT NOT NULL, PRIMARY KEY (c,d),
+FOREIGN KEY (c) REFERENCES t1 (a,k) ON UPDATE NO ACTION) engine=innodb;
+ERROR 42000: Incorrect foreign key definition for 'foreign key without name': Key reference and table reference don't match
+CREATE TABLE t2 (c INT NOT NULL, d INT NOT NULL, PRIMARY KEY (c,d),
+FOREIGN KEY f1 (c) REFERENCES t1 (a,k) ON UPDATE NO ACTION) engine=innodb;
+ERROR 42000: Incorrect foreign key definition for 'f1': Key reference and table reference don't match
+CREATE TABLE t2 (c INT NOT NULL, d INT NOT NULL, PRIMARY KEY (c,d),
+CONSTRAINT c1 FOREIGN KEY f1 (c) REFERENCES t1 (a) ON DELETE NO ACTION,
+CONSTRAINT c2 FOREIGN KEY (c) REFERENCES t1 (a) ON UPDATE NO ACTION,
+FOREIGN KEY f3 (c) REFERENCES t1 (a) ON UPDATE NO ACTION,
+FOREIGN KEY (c) REFERENCES t1 (a) ON UPDATE NO ACTION) engine=innodb;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `c` int(11) NOT NULL,
+  `d` int(11) NOT NULL,
+  PRIMARY KEY (`c`,`d`),
+  CONSTRAINT `c1` FOREIGN KEY (`c`) REFERENCES `t1` (`a`) ON DELETE NO ACTION,
+  CONSTRAINT `c2` FOREIGN KEY (`c`) REFERENCES `t1` (`a`) ON UPDATE NO ACTION,
+  CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`c`) REFERENCES `t1` (`a`) ON UPDATE NO ACTION,
+  CONSTRAINT `t2_ibfk_2` FOREIGN KEY (`c`) REFERENCES `t1` (`a`) ON UPDATE NO ACTION
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+DROP TABLE t2;
+DROP TABLE t1;
 End of 5.1 tests

sql/sql_yacc.yy

@@ -4656,8 +4656,9 @@ key_def:
         | opt_constraint FOREIGN KEY_SYM opt_ident '(' key_list ')' references
           {
             LEX *lex=Lex;
-            const char *key_name= $4 ? $4 : $1;
-            Key *key= new Foreign_key(key_name, lex->col_list,
+            const char *key_name= $1 ? $1 : $4;
+            const char *fkey_name = $4 ? $4 : key_name;
+            Key *key= new Foreign_key(fkey_name, lex->col_list,
                                       $8,
                                       lex->ref_list,
                                       lex->fk_delete_opt,