/**
* 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.hadoop.hive.ql.udf.generic;
import java.util.ArrayList;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.WindowFunctionDescription;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.ql.plan.ptf.WindowFrameDef;
import org.apache.hadoop.hive.ql.udf.generic.GenericUDAFEvaluator.AggregationBuffer;
import org.apache.hadoop.hive.ql.udf.generic.GenericUDAFLead.GenericUDAFLeadEvaluator;
import org.apache.hadoop.hive.ql.udf.generic.GenericUDAFLead.GenericUDAFLeadEvaluatorStreaming;
import org.apache.hadoop.hive.ql.udf.generic.GenericUDAFLead.LeadBuffer;
import org.apache.hadoop.hive.ql.udf.generic.GenericUDAFLeadLag.GenericUDAFLeadLagEvaluator;
@WindowFunctionDescription
(
description = @Description(
name = "lag",
value = "_FUNC_(expr, amt, default)"
),
supportsWindow = false,
pivotResult = true,
impliesOrder = true
)
public class GenericUDAFLag extends GenericUDAFLeadLag {
static final Logger LOG = LoggerFactory.getLogger(GenericUDAFLag.class.getName());
@Override
protected String functionName() {
return "Lag";
}
@Override
protected GenericUDAFLeadLagEvaluator createLLEvaluator() {
return new GenericUDAFLagEvaluator();
}
public static class GenericUDAFLagEvaluator extends GenericUDAFLeadLagEvaluator {
public GenericUDAFLagEvaluator() {
}
/*
* used to initialize Streaming Evaluator.
*/
protected GenericUDAFLagEvaluator(GenericUDAFLeadLagEvaluator src) {
super(src);
}
@Override
protected LeadLagBuffer getNewLLBuffer() throws HiveException {
return new LagBuffer();
}
@Override
public GenericUDAFEvaluator getWindowingEvaluator(WindowFrameDef wFrmDef) {
return new GenericUDAFLagEvaluatorStreaming(this);
}
}
static class LagBuffer implements LeadLagBuffer {
ArrayList<Object> values;
int lagAmt;
ArrayList<Object> lagValues;
int lastRowIdx;
public void initialize(int lagAmt) {
this.lagAmt = lagAmt;
lagValues = new ArrayList<Object>(lagAmt);
values = new ArrayList<Object>();
lastRowIdx = -1;
}
public void addRow(Object currValue, Object defaultValue) {
int row = lastRowIdx + 1;
if ( row < lagAmt) {
lagValues.add(defaultValue);
}
values.add(currValue);
lastRowIdx++;
}
public Object terminate() {
/*
* if partition is smaller than the lagAmt;
* the entire partition is in lagValues.
*/
if ( values.size() < lagAmt ) {
values = lagValues;
return lagValues;
}
int lastIdx = values.size() - 1;
for(int i = 0; i < lagAmt; i++) {
values.remove(lastIdx - i);
}
values.addAll(0, lagValues);
return values;
}
}
/*
* StreamingEval: wrap regular eval. on getNext remove first row from values
* and return it.
*/
static class GenericUDAFLagEvaluatorStreaming extends GenericUDAFLagEvaluator
implements ISupportStreamingModeForWindowing {
protected GenericUDAFLagEvaluatorStreaming(GenericUDAFLeadLagEvaluator src) {
super(src);
}
@Override
public Object getNextResult(AggregationBuffer agg) throws HiveException {
LagBuffer lb = (LagBuffer) agg;
if (!lb.lagValues.isEmpty()) {
Object res = lb.lagValues.remove(0);
if (res == null) {
return ISupportStreamingModeForWindowing.NULL_RESULT;
}
return res;
} else if (!lb.values.isEmpty()) {
Object res = lb.values.remove(0);
if (res == null) {
return ISupportStreamingModeForWindowing.NULL_RESULT;
}
return res;
}
return null;
}
@Override
public int getRowsRemainingAfterTerminate() throws HiveException {
return getAmt();
}
}
}