@Override
  public int execute() throws Exception {
    Table table = context.getDb().getTable(desc.getFullTableName());
    context.getDb().alterTableExecuteOperation(table, desc.getExecuteSpec());
    return 0;
  }
Operation process of ALTER TABLE ... EXECUTE command
ql/src/java/org/apache/hadoop/hive/ql/ddl/table/execute/AlterTableExecuteOperation.java