better fix for bug#3749 - do not consider already removed keys in key removal process

mysql-test/r/innodb.result:
  tests for bug#3749
mysql-test/t/innodb.test:
  tests for bug#3749

mysql-test/r/innodb.result

@@ -1540,4 +1540,27 @@ t2	CREATE TABLE `t2` (
 drop table t2;
 create table t2 (id int(11) not null, id2 int(11) not null, constraint t1_id_fk foreign key (id2,id) references t1 (id)) engine = innodb;
 ERROR HY000: Can't create table './test/t2.frm' (errno: 150)
-drop table t1;
+create table t2 (a int auto_increment primary key, b int, index(b), foreign key (b) references t1(id), unique(b)) engine=innodb;
+show create table t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `a` int(11) NOT NULL auto_increment,
+  `b` int(11) default NULL,
+  PRIMARY KEY  (`a`),
+  UNIQUE KEY `b_2` (`b`),
+  KEY `b` (`b`),
+  CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`b`) REFERENCES `t1` (`id`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+drop table t2;
+create table t2 (a int auto_increment primary key, b int, foreign key (b) references t1(id), foreign key (b) references t1(id), unique(b)) engine=innodb;
+show create table t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `a` int(11) NOT NULL auto_increment,
+  `b` int(11) default NULL,
+  PRIMARY KEY  (`a`),
+  UNIQUE KEY `b` (`b`),
+  CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`b`) REFERENCES `t1` (`id`),
+  CONSTRAINT `t2_ibfk_2` FOREIGN KEY (`b`) REFERENCES `t1` (`id`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+drop table t2, t1;

mysql-test/t/innodb.test

@@ -1086,4 +1086,14 @@ drop table t2;
 --error 1005
 create table t2 (id int(11) not null, id2 int(11) not null, constraint t1_id_fk foreign key (id2,id) references t1 (id)) engine = innodb;
 
-drop table t1;
+# bug#3749
+
+create table t2 (a int auto_increment primary key, b int, index(b), foreign key (b) references t1(id), unique(b)) engine=innodb;
+show create table t2;
+drop table t2;
+create table t2 (a int auto_increment primary key, b int, foreign key (b) references t1(id), foreign key (b) references t1(id), unique(b)) engine=innodb;
+show create table t2;
+drop table t2, t1;
+
+
+

sql/sql_table.cc

@@ -688,28 +688,21 @@ int mysql_prepare_table(THD *thd, HA_CREATE_INFO *create_info,
 	'generated', and a generated key is a prefix of the other key. Then we
 	do not need the generated shorter key.
         */
-        if ((key2->type != Key::FOREIGN_KEY && !foreign_key_prefix(key, key2)))
+        if (key2->name != ignore_key && key2->type != Key::FOREIGN_KEY &&
+            !foreign_key_prefix(key, key2))
         {
-          /* TO DO: issue warning message */
+          /* TODO: issue warning message */
           /* mark that the generated key should be ignored */
           if (!key2->generated ||
               (key->generated && key->columns.elements <
                key2->columns.elements))
             key->name= ignore_key;
           else
-          {
-            /*
-	    Remove the previous, generated key if it has not yet been
-	    removed. Note that if we have several identical generated keys,
-            the last one will remain and others get removed here.
-	    */
-            if (key2->name != ignore_key)
           {
             key2->name= ignore_key;
             key_parts-= key2->columns.elements;
             (*key_count)--;
           }
-          }
           break;
         }
       }