core/src/main/java/org/apache/calcite/sql/fun/SqlFirstLastValueAggFunction.java

/*
 * 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.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 java.util.List;

import static com.google.common.base.Preconditions.checkArgument;

/**
 * <code>FIRST_VALUE</code> and <code>LAST_VALUE</code> aggregate functions
 * return the first or the last value in a list of values that are input to the
 * function.
 */
public class SqlFirstLastValueAggFunction extends SqlAggFunction {
  //~ Constructors -----------------------------------------------------------

  public SqlFirstLastValueAggFunction(SqlKind kind) {
    super(
        kind.name(),
        null,
        kind,
        ReturnTypes.ARG0_NULLABLE_IF_EMPTY,
        null,
        OperandTypes.ANY,
        SqlFunctionCategory.NUMERIC,
        false,
        true,
        Optionality.FORBIDDEN);
    checkArgument(kind == SqlKind.FIRST_VALUE || kind == SqlKind.LAST_VALUE);
  }

  @Deprecated // to be removed before 2.0
  public SqlFirstLastValueAggFunction(boolean firstFlag) {
    this(firstFlag ? SqlKind.FIRST_VALUE : SqlKind.LAST_VALUE);
  }

  //~ 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 boolean allowsNullTreatment() {
    return true;
  }
}