/*
* 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 = "lag", typeVariable = "T", returnType = "T", argumentTypes = "T")
@WindowFunctionSignature(name = "lag", typeVariable = "T", returnType = "T", argumentTypes = {"T", "bigint"})
@WindowFunctionSignature(name = "lag", typeVariable = "T", returnType = "T", argumentTypes = {"T", "bigint", "T"})
public class LagFunction
extends ValueWindowFunction
{
private final int valueChannel;
private final int offsetChannel;
private final int defaultChannel;
public LagFunction(List<Integer> argumentChannels)
{
this.valueChannel = argumentChannels.get(0);
this.offsetChannel = (argumentChannels.size() > 1) ? argumentChannels.get(1) : -1;
this.defaultChannel = (argumentChannels.size() > 2) ? argumentChannels.get(2) : -1;
}
@Override
public void processRow(BlockBuilder output, int frameStart, int frameEnd, int currentPosition)
{
if ((offsetChannel >= 0) && windowIndex.isNull(offsetChannel, currentPosition)) {
output.appendNull();
}
else {
long offset = (offsetChannel < 0) ? 1 : windowIndex.getLong(offsetChannel, currentPosition);
checkCondition(offset >= 0, INVALID_FUNCTION_ARGUMENT, "Offset must be at least 0");
long valuePosition = currentPosition - offset;
if ((valuePosition >= 0) && (valuePosition <= currentPosition)) {
windowIndex.appendTo(valueChannel, toIntExact(valuePosition), output);
}
else if (defaultChannel >= 0) {
windowIndex.appendTo(defaultChannel, currentPosition, output);
}
else {
output.appendNull();
}
}
}
}