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.adapter.enumerable;
  
  import org.apache.calcite.linq4j.tree.Expression;
  
  /**
   * Provides information on the current window.
   *
   * <p>All the indexes are ready to be used in
   * {@link WinAggResultContext#arguments(org.apache.calcite.linq4j.tree.Expression)},
   * {@link WinAggFrameResultContext#rowTranslator(org.apache.calcite.linq4j.tree.Expression)}
   * and similar methods.
   */
  public interface WinAggFrameContext {
    /**
     * Returns the index of the current row in the partition.
     * In other words, it is close to ~ROWS BETWEEN CURRENT ROW.
     * Note to use {@link #startIndex()} when you need zero-based row position.
     *
     * @return the index of the very first row in partition
     */
    Expression index();
  
    /**
     * Returns the index of the very first row in partition.
     *
     * @return index of the very first row in partition
     */
    Expression startIndex();
  
    /**
     * Returns the index of the very last row in partition.
     *
     * @return index of the very last row in partition
     */
    Expression endIndex();
  
    /**
     * Returns the boolean expression that tells if the partition has rows.
     * The partition might lack rows in cases like ROWS BETWEEN 1000 PRECEDING
     * AND 900 PRECEDING.
     *
     * @return boolean expression that tells if the partition has rows
     */
    Expression hasRows();
  
    /**
     * Returns the number of rows in the current frame (subject to framing
     * clause).
     *
     * @return number of rows in the current partition or 0 if the partition
     *   is empty
     */
    Expression getFrameRowCount();
  
    /**
     * Returns the number of rows in the current partition (as determined by
     * PARTITION BY clause).
     *
     * @return number of rows in the current partition or 0 if the partition
     *   is empty
     */
    Expression getPartitionRowCount();
  }
  