[DBAL-586] Fix failures introduced by PR and adjust code.

lib/Doctrine/DBAL/Platforms/MySqlPlatform.php

@@ -642,15 +642,6 @@ class MySqlPlatform extends AbstractPlatform
                 }
             }
         }
-        foreach ($diff->changedIndexes as $changedKey => $changedIndex) {
-            if ($changedIndex->isPrimary() && $changedKey != 'PRIMARY') {
-                $index = $diff->changedIndexes[$changedKey];
-                $index = new Index($changedKey, $index->getColumns(), $index->isUnique(), false);
-                $diff->removedIndexes[$changedKey] = $index;
-                $diff->addedIndexes['PRIMARY'] = $diff->changedIndexes[$changedKey];
-                unset($diff->changedIndexes[$changedKey]);
-            }
-        }
 
         $sql = array_merge($sql, parent::getPreAlterTableIndexForeignKeySQL($diff));
 

tests/Doctrine/Tests/DBAL/Platforms/MySqlPlatformTest.php

@@ -314,7 +314,7 @@ class MySqlPlatformTest extends AbstractPlatformTestCase
         $diffTable->setPrimaryKey(array('id'));
 
         $this->assertEquals(
-            array('ALTER TABLE alter_table_add_pk DROP INDEX idx_id, ADD PRIMARY KEY (id)'),
+            array('DROP INDEX idx_id ON alter_table_add_pk', 'ALTER TABLE alter_table_add_pk ADD PRIMARY KEY (id)'),
             $this->_platform->getAlterTableSQL($comparator->diffTable($table, $diffTable))
         );
     }
@@ -375,7 +375,7 @@ class MySqlPlatformTest extends AbstractPlatformTestCase
         $sql = $this->_platform->getAlterTableSQL($diff);
 
         $this->assertEquals(array(
-	    "DROP INDEX foo_index ON mytable",
+	        "ALTER TABLE mytable DROP PRIMARY KEY",
             "ALTER TABLE mytable ADD PRIMARY KEY (foo)",
         ), $sql);
     }