fix index drop on pg

lib/pgsqlschema.php

@@ -334,6 +334,20 @@ class PgsqlSchema extends Schema
         }
     }
 
+    /**
+     * Append an SQL statement to drop an index from a table.
+     * Note that in PostgreSQL, index names are DB-unique.
+     *
+     * @param array $statements
+     * @param string $table
+     * @param string $name
+     * @param array $def
+     */
+    function appendDropIndex(array &$statements, $table, $name)
+    {
+        $statements[] = "DROP INDEX $name";
+    }
+
     /**
      * Quote a db/table/column identifier if necessary.
      *