UDTF 示例和用法

用户定义的表函数由 org.apache.hadoop.hive.ql.udf.generic.GenericUDTF 接口表示。此功能允许为单个输入输出多行和多列。

我们必须覆盖以下方法：

 1.we specify input and output parameters
abstract StructObjectInspector initialize(ObjectInspector[] args) 
                                                throws UDFArgumentException; 

 2.we process an input record and write out any resulting records 
abstract void process(Object[] record) throws HiveException;

3.function is Called to notify the UDTF that there are no more rows to process. 
    Clean up code or additional output can be produced here.
abstract void close() throws HiveException;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.apache.hadoop.hive.ql.exec.UDFArgumentException;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.ql.udf.generic.GenericUDTF;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorFactory;
import org.apache.hadoop.hive.serde2.objectinspector.PrimitiveObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.StructObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorFactory;

public class NameParserGenericUDTF extends GenericUDTF {
      private PrimitiveObjectInspector stringOI = null;
      
       //Defining input argument as string.
      @Override
      public StructObjectInspector initialize(ObjectInspector[] args) throws UDFArgumentException {
        if (args.length != 1) {
          throw new UDFArgumentException("NameParserGenericUDTF() takes exactly one argument");
        }

        if (args[0].getCategory() != ObjectInspector.Category.PRIMITIVE
            && ((PrimitiveObjectInspector) args[0]).getPrimitiveCategory() != PrimitiveObjectInspector.PrimitiveCategory.STRING) {
          throw new UDFArgumentException("NameParserGenericUDTF() takes a string as a parameter");
        }
        
        // input
        stringOI = (PrimitiveObjectInspector) args[0];

        // output 
        List<String> fieldNames = new ArrayList<String>(2);
        List<ObjectInspector> fieldOIs = new ArrayList<ObjectInspector>(2);
        fieldNames.add("name");
        fieldNames.add("surname");
        fieldOIs.add(PrimitiveObjectInspectorFactory.javaStringObjectInspector);
        fieldOIs.add(PrimitiveObjectInspectorFactory.javaStringObjectInspector);
        return ObjectInspectorFactory.getStandardStructObjectInspector(fieldNames, fieldOIs);
      }
            
      public ArrayList<Object[]> processInputRecord(String name){
            ArrayList<Object[]> result = new ArrayList<Object[]>();
          
            // ignoring null or empty input
            if (name == null || name.isEmpty()) {
              return result;
            }
            
            String[] tokens = name.split("\\s+");
            
            if (tokens.length == 2){
                result.add(new Object[] { tokens[0], tokens[1] });
            }else if (tokens.length == 4 && tokens[1].equals("and")){
                result.add(new Object[] { tokens[0], tokens[3] });
                result.add(new Object[] { tokens[2], tokens[3] });
            }
            
            return result;
      }
      
      @Override
      public void process(Object[] record) throws HiveException {
        final String name = stringOI.getPrimitiveJavaObject(record[0]).toString();
        ArrayList<Object[]> results = processInputRecord(name);
        
        Iterator<Object[]> it = results.iterator();
        
        while (it.hasNext()){
            Object[] r = it.next();
            forward(r);
        }
      }

      @Override
      public void close() throws HiveException {
        // do nothing
      }
}

将代码打包到 jar 中，需要将 jar 添加到 hive 上下文中。

hive> CREATE TEMPORARY FUNCTION process_names as 'jar.path.NameParserGenericUDTF'; 

Here we will pass input as full name and break it into first and last name.

hive> SELECT 
   t.name,
   t.surname 
FROM people 
    lateral view process_names(name) t as name, surname;

Teena Carter
John Brownewr