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.SqlTypeName;
  import org.apache.calcite.util.Optionality;
  
  import com.google.common.collect.ImmutableList;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.List;
  
  /**
   * <code>Sum0</code> is an aggregator which returns the sum of the values which
   * go into it like <code>Sum</code>. It differs in that when no non null values
   * are applied zero is returned instead of null. Can be used along with <code>
   * Count</code> to implement <code>Sum</code>.
   */
  public class SqlSumEmptyIsZeroAggFunction extends SqlAggFunction {
    //~ Constructors -----------------------------------------------------------
  
    public SqlSumEmptyIsZeroAggFunction() {
      super("$SUM0",
          null,
          SqlKind.SUM0,
          ReturnTypes.AGG_SUM_EMPTY_IS_ZERO,
          null,
          OperandTypes.NUMERIC,
          SqlFunctionCategory.NUMERIC,
          false,
          false,
          Optionality.FORBIDDEN);
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @SuppressWarnings("deprecation")
    @Override public List<RelDataType> getParameterTypes(RelDataTypeFactory typeFactory) {
      return ImmutableList.of(
          typeFactory.createTypeWithNullability(
              typeFactory.createSqlType(SqlTypeName.ANY), true));
    }
  
    @SuppressWarnings("deprecation")
    @Override public RelDataType getReturnType(RelDataTypeFactory typeFactory) {
      return typeFactory.createTypeWithNullability(
          typeFactory.createSqlType(SqlTypeName.ANY), true);
    }
  
    @Override public <T extends Object> @Nullable T unwrap(Class<T> clazz) {
      if (clazz.isInstance(SqlSplittableAggFunction.Sum0Splitter.INSTANCE)) {
        return clazz.cast(SqlSplittableAggFunction.Sum0Splitter.INSTANCE);
      }
      return super.unwrap(clazz);
    }
  
    @Override public SqlAggFunction getRollup() {
      return this;
    }
  }
  