/*
* Licensed 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.facebook.presto.operator.window;
import com.facebook.presto.spi.block.BlockBuilder;
import com.facebook.presto.spi.function.ValueWindowFunction;
import com.facebook.presto.spi.function.WindowFunctionSignature;
import java.util.List;
import static com.facebook.presto.spi.StandardErrorCode.INVALID_FUNCTION_ARGUMENT;
import static com.facebook.presto.util.Failures.checkCondition;
import static java.lang.Math.toIntExact;
@WindowFunctionSignature(name = "nth_value", typeVariable = "T", returnType = "T", argumentTypes = {"T", "bigint"})
public class NthValueFunction
extends ValueWindowFunction
{
private final int valueChannel;
private final int offsetChannel;
public NthValueFunction(List<Integer> argumentChannels)
{
this.valueChannel = argumentChannels.get(0);
this.offsetChannel = argumentChannels.get(1);
}
@Override
public void processRow(BlockBuilder output, int frameStart, int frameEnd, int currentPosition)
{
if ((frameStart < 0) || windowIndex.isNull(offsetChannel, currentPosition)) {
output.appendNull();
}
else {
long offset = windowIndex.getLong(offsetChannel, currentPosition);
checkCondition(offset >= 1, INVALID_FUNCTION_ARGUMENT, "Offset must be at least 1");
// offset is base 1
long valuePosition = frameStart + (offset - 1);
if ((valuePosition >= frameStart) && (valuePosition <= frameEnd)) {
windowIndex.appendTo(valueChannel, toIntExact(valuePosition), output);
}
else {
output.appendNull();
}
}
}
}