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.sql.fun;
  
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rel.type.RelDataTypeFactory;
  import org.apache.calcite.sql.SqlAggFunction;
  import org.apache.calcite.sql.SqlFunctionCategory;
  import org.apache.calcite.sql.SqlKind;
  import org.apache.calcite.sql.SqlSplittableAggFunction;
  import org.apache.calcite.sql.type.OperandTypes;
  import org.apache.calcite.sql.type.ReturnTypes;
  import org.apache.calcite.sql.type.SqlOperandTypeChecker;
  import org.apache.calcite.util.Optionality;
  
  import com.google.common.collect.ImmutableList;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.List;
  
  import static com.google.common.base.Preconditions.checkArgument;
  
  /**
   * Definition of the <code>MIN</code> and <code>MAX</code> aggregate functions,
   * returning the returns the smallest/largest of the values which go into it.
   *
   * <p>There are 3 forms:
   *
   * <dl>
   * <dt>min/max(<em>primitive type</em>)
   * <dd>values are compared using '&lt;'
   *
   * <dt>min/max({@link java.lang.Comparable})
   * <dd>values are compared using {@link java.lang.Comparable#compareTo}
   *
   * <dt>min/max({@link java.util.Comparator}, {@link java.lang.Object})
   * <dd>the {@link java.util.Comparator#compare} method of the comparator is used
   * to compare pairs of objects. The comparator is a startup argument, and must
   * therefore be constant for the duration of the aggregation.
   * </dl>
   */
  public class SqlMinMaxAggFunction extends SqlAggFunction {
    //~ Static fields/initializers ---------------------------------------------
  
    public static final int MINMAX_INVALID = -1;
    public static final int MINMAX_PRIMITIVE = 0;
    public static final int MINMAX_COMPARABLE = 1;
    public static final int MINMAX_COMPARATOR = 2;
  
    //~ Instance fields --------------------------------------------------------
  
    @Deprecated // to be removed before 2.0
    public final List<RelDataType> argTypes;
    private final int minMaxKind;
  
    //~ Constructors -----------------------------------------------------------
  
    /** Creates a SqlMinMaxAggFunction. */
    public SqlMinMaxAggFunction(SqlKind kind) {
      this(kind.name(), kind, OperandTypes.COMPARABLE_ORDERED);
    }
  
    /** Creates a SqlMinMaxAggFunction. */
    public SqlMinMaxAggFunction(String funcName, SqlKind kind,
        SqlOperandTypeChecker inputTypeChecker) {
      super(funcName,
          null,
          kind,
          ReturnTypes.ARG0_NULLABLE_IF_EMPTY,
          null,
          inputTypeChecker,
          SqlFunctionCategory.SYSTEM,
          false,
          false,
          Optionality.FORBIDDEN);
      this.argTypes = ImmutableList.of();
      this.minMaxKind = MINMAX_COMPARABLE;
      checkArgument(kind == SqlKind.MIN || kind == SqlKind.MAX);
    }
  
    @Deprecated // to be removed before 2.0
    public SqlMinMaxAggFunction(
        List<RelDataType> argTypes,
        boolean isMin,
        int minMaxKind) {
      this(isMin ? SqlKind.MIN : SqlKind.MAX);
      assert argTypes.isEmpty();
      assert minMaxKind == MINMAX_COMPARABLE;
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Deprecated // to be removed before 2.0
    public boolean isMin() {
      return kind == SqlKind.MIN;
    }
  
    @Deprecated // to be removed before 2.0
    public int getMinMaxKind() {
      return minMaxKind;
    }
  
    @Override public Optionality getDistinctOptionality() {
      return Optionality.IGNORED;
    }
  
    @SuppressWarnings("deprecation")
    @Override public List<RelDataType> getParameterTypes(RelDataTypeFactory typeFactory) {
      switch (minMaxKind) {
      case MINMAX_PRIMITIVE:
      case MINMAX_COMPARABLE:
        return argTypes;
      case MINMAX_COMPARATOR:
        return argTypes.subList(1, 2);
      default:
        throw new AssertionError("bad kind: " + minMaxKind);
      }
    }
  
    @SuppressWarnings("deprecation")
    @Override public RelDataType getReturnType(RelDataTypeFactory typeFactory) {
      switch (minMaxKind) {
      case MINMAX_PRIMITIVE:
      case MINMAX_COMPARABLE:
        return argTypes.get(0);
      case MINMAX_COMPARATOR:
        return argTypes.get(1);
      default:
        throw new AssertionError("bad kind: " + minMaxKind);
      }
    }
  
    @Override public <T extends Object> @Nullable T unwrap(Class<T> clazz) {
      if (clazz.isInstance(SqlSplittableAggFunction.SelfSplitter.INSTANCE)) {
        return clazz.cast(SqlSplittableAggFunction.SelfSplitter.INSTANCE);
      }
      return super.unwrap(clazz);
    }
  
    @Override public SqlAggFunction getRollup() {
      return this;
    }
  }
  