/*
* 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.pig.builtin;
import java.io.IOException;
import java.math.BigDecimal;
import java.math.MathContext;
import java.util.Iterator;
import org.apache.pig.Accumulator;
import org.apache.pig.Algebraic;
import org.apache.pig.EvalFunc;
import org.apache.pig.PigException;
import org.apache.pig.backend.executionengine.ExecException;
import org.apache.pig.data.DataBag;
import org.apache.pig.data.DataType;
import org.apache.pig.data.Tuple;
import org.apache.pig.data.TupleFactory;
import org.apache.pig.impl.logicalLayer.schema.Schema;
/**
* This method should never be used directly, use {@link AVG}.
*/
public class BigDecimalAvg extends EvalFunc<BigDecimal> implements Algebraic, Accumulator<BigDecimal> {
private static TupleFactory mTupleFactory = TupleFactory.getInstance();
@Override
public BigDecimal exec(Tuple input) throws IOException {
try {
BigDecimal sum = sum(input);
if (sum == null) {
// either we were handed an empty bag or a bag
// filled with nulls - return null in this case
return null;
}
BigDecimal count = count(input);
BigDecimal avg = null;
if (count.compareTo(BigDecimal.ZERO) > 0)
avg = div(sum, count);
return avg;
} catch (ExecException ee) {
throw ee;
}
}
@Override
public String getInitial() {
return Initial.class.getName();
}
@Override
public String getIntermed() {
return Intermediate.class.getName();
}
@Override
public String getFinal() {
return Final.class.getName();
}
static public class Initial extends EvalFunc<Tuple> {
@Override
public Tuple exec(Tuple input) throws IOException {
try {
Tuple t = mTupleFactory.newTuple(2);
// input is a bag with one tuple containing
// the column we are trying to avg on
DataBag bg = (DataBag) input.get(0);
BigDecimal d = null;
if (bg.iterator().hasNext()) {
Tuple tp = bg.iterator().next();
d = (BigDecimal)(tp.get(0));
}
t.set(0, d);
if (d != null) {
t.set(1, BigDecimal.ONE);
} else {
t.set(1, BigDecimal.ZERO);
}
return t;
} catch (ExecException ee) {
throw ee;
} catch (Exception e) {
int errCode = 2106;
String msg = "Error while computing average in " + this.getClass().getSimpleName();
throw new ExecException(msg, errCode, PigException.BUG, e);
}
}
}
static public class Intermediate extends EvalFunc<Tuple> {
@Override
public Tuple exec(Tuple input) throws IOException {
try {
DataBag b = (DataBag)input.get(0);
return combine(b);
} catch (ExecException ee) {
throw ee;
} catch (Exception e) {
int errCode = 2106;
String msg = "Error while computing average in " + this.getClass().getSimpleName();
throw new ExecException(msg, errCode, PigException.BUG, e);
}
}
}
static public class Final extends EvalFunc<BigDecimal> {
@Override
public BigDecimal exec(Tuple input) throws IOException {
try {
DataBag b = (DataBag)input.get(0);
Tuple combined = combine(b);
BigDecimal sum = (BigDecimal)combined.get(0);
if (sum == null) {
return null;
}
BigDecimal count = (BigDecimal)combined.get(1);
BigDecimal avg = null;
if (count.compareTo(BigDecimal.ZERO) > 0) {
avg = div(sum,count);
}
return avg;
} catch (ExecException ee) {
throw ee;
} catch (Exception e) {
int errCode = 2106;
String msg = "Error while computing average in " + this.getClass().getSimpleName();
throw new ExecException(msg, errCode, PigException.BUG, e);
}
}
}
static protected Tuple combine(DataBag values) throws ExecException {
BigDecimal sum = BigDecimal.ZERO;
BigDecimal count = BigDecimal.ZERO;
// combine is called from Intermediate and Final
// In either case, Initial would have been called
// before and would have sent in valid tuples
// Hence we don't need to check if incoming bag
// is empty
Tuple output = mTupleFactory.newTuple(2);
boolean sawNonNull = false;
for (Iterator<Tuple> it = values.iterator(); it.hasNext();) {
Tuple t = it.next();
BigDecimal d = (BigDecimal)t.get(0);
// we count nulls in avg as contributing 0
// a departure from SQL for performance of
// COUNT() which implemented by just inspecting
// size of the bag
if (d == null) {
d = BigDecimal.ZERO;
} else {
sawNonNull = true;
}
sum = sum.add(d);
count = count.add((BigDecimal)t.get(1));
}
if (sawNonNull) {
output.set(0, sum);
} else {
output.set(0, null);
}
output.set(1, count);
return output;
}
static protected BigDecimal count(Tuple input) throws ExecException {
DataBag values = (DataBag)input.get(0);
Iterator<Tuple> it = values.iterator();
BigDecimal cnt = BigDecimal.ZERO;
while (it.hasNext()){
Tuple t = (Tuple)it.next();
if (t != null && t.size() > 0 && t.get(0) != null)
cnt = cnt.add(BigDecimal.ONE);
}
return cnt;
}
static protected BigDecimal sum(Tuple input) throws ExecException, IOException {
DataBag values = (DataBag)input.get(0);
// if we were handed an empty bag, return NULL
if(values == null || values.size() == 0) {
return null;
}
BigDecimal sum = BigDecimal.ZERO;
boolean sawNonNull = false;
for (Iterator<Tuple> it = values.iterator(); it.hasNext();) {
Tuple t = it.next();
try{
BigDecimal d = (BigDecimal)(t.get(0));
if (d == null) continue;
sawNonNull = true;
sum = sum.add(d);
}catch(RuntimeException exp) {
int errCode = 2103;
String msg = "Problem while computing sum of BigDecimals.";
throw new ExecException(msg, errCode, PigException.BUG, exp);
}
}
if(sawNonNull) {
return sum;
} else {
return null;
}
}
static protected BigDecimal div(BigDecimal dividend, BigDecimal divisor){
// Averages will have IEEE 754R Decimal64 format, 16 digits, and a
// rounding mode of HALF_EVEN, the IEEE 754R default
return dividend.divide(divisor, MathContext.DECIMAL128);
}
@Override
public Schema outputSchema(Schema input) {
return new Schema(new Schema.FieldSchema(null, DataType.BIGDECIMAL));
}
/* Accumulator interface */
private BigDecimal intermediateSum = null;
private BigDecimal intermediateCount = null;
@Override
public void accumulate(Tuple b) throws IOException {
try {
BigDecimal sum = sum(b);
if(sum == null) {
return;
}
// set default values
if (intermediateSum == null || intermediateCount == null) {
intermediateSum = BigDecimal.ZERO;
intermediateCount = BigDecimal.ZERO;
}
BigDecimal count = (BigDecimal)count(b);
if (count.compareTo(BigDecimal.ZERO) > 0) {
intermediateCount = intermediateCount.add(count);
intermediateSum = intermediateSum.add(sum);
}
} catch (ExecException ee) {
throw ee;
} catch (Exception e) {
int errCode = 2106;
String msg = "Error while computing average in " + this.getClass().getSimpleName();
throw new ExecException(msg, errCode, PigException.BUG, e);
}
}
@Override
public void cleanup() {
intermediateSum = null;
intermediateCount = null;
}
@Override
public BigDecimal getValue() {
BigDecimal avg = null;
if (intermediateCount != null && (intermediateCount.compareTo(BigDecimal.ZERO) > 0)) {
avg = div(intermediateSum,intermediateCount);
}
return avg;
}
}