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.model;
  
  import com.fasterxml.jackson.annotation.JsonCreator;
  import com.fasterxml.jackson.annotation.JsonProperty;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * An aggregate function applied to a column (or columns) of a lattice.
   *
   * <p>Occurs in a {@link org.apache.calcite.model.JsonTile},
   * and there is a default list in
   * {@link org.apache.calcite.model.JsonLattice}.
   *
   * @see JsonRoot Description of schema elements
   */
  public class JsonMeasure {
    /** The name of an aggregate function.
     *
     * <p>Required. Usually {@code count}, {@code sum},
     * {@code min}, {@code max}.
     */
    public final String agg;
  
    /** Arguments to the measure.
     *
     * <p>Valid values are:
     * <ul>
     *   <li>Not specified: no arguments</li>
     *   <li>null: no arguments</li>
     *   <li>Empty list: no arguments</li>
     *   <li>String: single argument, the name of a lattice column</li>
     *   <li>List: multiple arguments, each a column name</li>
     * </ul>
     *
     * <p>Unlike lattice dimensions, measures can not be specified in qualified
     * format, {@code ["table", "column"]}. When you define a lattice, make sure
     * that each column you intend to use as a measure has a unique name within
     * the lattice (using "{@code AS alias}" if necessary).
     */
    public final @Nullable Object args;
  
    @JsonCreator
    public JsonMeasure(
        @JsonProperty(value = "agg", required = true) String agg,
        @JsonProperty("args") @Nullable Object args) {
      this.agg = requireNonNull(agg, "agg");
      this.args = args;
    }
  
    public void accept(ModelHandler modelHandler) {
      modelHandler.visit(this);
    }
  }
  