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SQL Parser and Optimizer
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/*
 * 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 com.hazelcast.org.apache.calcite.sql.fun;

import com.hazelcast.org.apache.calcite.rel.type.RelDataType;
import com.hazelcast.org.apache.calcite.rel.type.RelDataTypeFactory;
import com.hazelcast.org.apache.calcite.sql.SqlAggFunction;
import com.hazelcast.org.apache.calcite.sql.SqlFunctionCategory;
import com.hazelcast.org.apache.calcite.sql.SqlKind;
import com.hazelcast.org.apache.calcite.sql.SqlSplittableAggFunction;
import com.hazelcast.org.apache.calcite.sql.type.OperandTypes;
import com.hazelcast.org.apache.calcite.sql.type.ReturnTypes;
import com.hazelcast.org.apache.calcite.sql.type.SqlTypeName;
import com.hazelcast.org.apache.calcite.util.Optionality;

import com.hazelcast.com.google.common.collect.ImmutableList;

import com.hazelcast.org.checkerframework.checker.nullness.qual.Nullable;

import java.util.List;

/**
 * Sum0 is an aggregator which returns the sum of the values which
 * go into it like Sum. It differs in that when no non null values
 * are applied zero is returned instead of null. Can be used along with 
 * Count to implement Sum.
 */
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 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  @Nullable T unwrap(Class clazz) {
    if (clazz == SqlSplittableAggFunction.class) {
      return clazz.cast(SqlSplittableAggFunction.Sum0Splitter.INSTANCE);
    }
    return super.unwrap(clazz);
  }

  @Override public SqlAggFunction getRollup() {
    return this;
  }
}