混合函数可以使用java中的方法java_method(class,method[,arg1[,arg2...]])或者reflect
Hive版本1.2.1
UDTF 用户定义表函数(表函数）一行变成多行配合lateral view
hive的Lateral view
http://blog.sina.com.cn/s/blog_7e04e0d00101csic.html
UDF 重写evaluate方法 Map端
import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.io.Text;
public class udftest extends UDF{
public boolean evaluate(Text t1,Text t2){
if(t1==null||t2==null){
return false;
}
double d1=Double.parseDouble(t1.toString());
double d2=Double.parseDouble(t2.toString());
if(d1>d2){
return true;
}else{
return false;
}
}
}
函数打包成function.jar
hive命令行
add jar /home/jar/function.jar //jar包进入分布式缓存 create temporary function bigthan as 'com.peixun.udf.udftest'//执行创建模版函数bigthan
UDAF (user defined aggregation function)用户自定义聚合函数
自定义UDAF统计b字段大于30的记录个数 countbigthan(b,30)实现代码
import org.apache.hadoop.hive.ql.exec.UDFArgumentTypeException;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.ql.parse.SemanticException;
import org.apache.hadoop.hive.ql.udf.generic.AbstractGenericUDAFResolver;
import org.apache.hadoop.hive.ql.udf.generic.GenericUDAFEvaluator;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.PrimitiveObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorFactory;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorUtils;
import org.apache.hadoop.hive.serde2.typeinfo.TypeInfo;
import org.apache.hadoop.io.LongWritable;
//继承类型检查类
public class udaftest extends AbstractGenericUDAFResolver {
// 参数个数判断
@Override
public GenericUDAFEvaluator getEvaluator(TypeInfo[] parameters)
throws SemanticException {
if (parameters.length != 2) {
throw new UDFArgumentTypeException(parameters.length - 1,
"Exactly two argument is expected");
}
return new GenericUDAFCountBigThanEvaluator();// 返回处理逻辑类
}
// 处理逻辑类
public static class GenericUDAFCountBigThanEvaluator extends
GenericUDAFEvaluator {
private LongWritable result;
private PrimitiveObjectInspector inputOI1;
private PrimitiveObjectInspector inputOI2;
// init方法map，reduce阶段都得执行
// map阶段parameters长度与UDAF输入的参数个数有关
// reduce阶段，parameters长度为1
@Override
public ObjectInspector init(Mode m, ObjectInspector[] parameters)
throws HiveException {
result = new LongWritable(0);
inputOI1 = (PrimitiveObjectInspector) parameters[0];
if (parameters.length > 1) {
inputOI2 = (PrimitiveObjectInspector) parameters[1];
}
return PrimitiveObjectInspectorFactory.writableLongObjectInspector;
// 最终结果返回类型
}
@Override
public AggregationBuffer getNewAggregationBuffer() throws HiveException {
CountAgg agg = new CountAgg();// 存放部分聚合值
reset(agg);
return agg;
}
// 缓存对象初始化
@Override
public void reset(AggregationBuffer agg) throws HiveException {
CountAgg countagg = (CountAgg) agg;
countagg.count = 0;
}
// 具体逻辑
// iterate只在map端运算
@Override
public void iterate(AggregationBuffer agg, Object[] parameters)
throws HiveException {
assert (parameters.length == 2);
if (parameters == null || parameters[0] == null
|| parameters[1] == null) {
return;
}
double base = PrimitiveObjectInspectorUtils.getDouble(
parameters[0], inputOI1);
double tmp = PrimitiveObjectInspectorUtils.getDouble(parameters[1],
inputOI2);
if (base > tmp) {
((CountAgg) agg).count++;
}
}
// map阶段返回部分结果
@Override
public Object terminatePartial(AggregationBuffer agg)
throws HiveException {
result.set(((CountAgg) agg).count);
return result;
}
// 合并部分结果 map(含有Combiner)和reduce都执行,parial传递terminatePartial得到的部分结果
@Override
public void merge(AggregationBuffer agg, Object partial)
throws HiveException {
if (partial != null) {
long p = PrimitiveObjectInspectorUtils.getLong(partial,
inputOI1);
((CountAgg) agg).count += p;
}
}
@Override
public Object terminate(AggregationBuffer agg) throws HiveException {
result.set(((CountAgg) agg).count);
return result;
}
public class CountAgg implements AggregationBuffer {
long count;
}
}
}
hive注册永久函数三种方法
hive shell每次启动都会默认执行$HOME/.hiverc文件
本文出自 “点滴积累” 博客，请务必保留此出处http://tianxingzhe.blog.51cto.com/3390077/1699735
