content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to you under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.calcite.schema;
  
  import org.apache.calcite.rel.type.RelDataTypeField;
  
  import java.util.List;
  
  /**
   * Table whose row type can be extended to include extra fields.
   *
   * <p>In some storage systems, especially those with "late schema", there may
   * exist columns that have values in the table but which are not declared in
   * the table schema. However, a particular query may wish to reference these
   * columns as if they were defined in the schema. Calling the {@link #extend}
   * method creates a temporarily extended table schema.
   *
   * <p>If the table implements extended interfaces such as
   * {@link org.apache.calcite.schema.ScannableTable},
   * {@link org.apache.calcite.schema.FilterableTable} or
   * {@link org.apache.calcite.schema.ProjectableFilterableTable}, you may wish
   * to make the table returned from {@link #extend} implement these interfaces
   * as well.
   */
  public interface ExtensibleTable extends Table {
    /** Returns a table that has the row type of this table plus the given
     * fields. */
    Table extend(List<RelDataTypeField> fields);
  
    /** Returns the starting offset of the first extended column, which may differ
     * from the field count when the table stores metadata columns that are not
     * counted in the row-type field count. */
    int getExtendedColumnOffset();
  }
  