hive 中udf,udaf,udtf

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UDF步骤：

1.继承org.apache.hadoop.hive.ql.exec.UDF
2.实现evaluate函数，evaluate函数支持重载
[java] view plain copy
package cn.sina.stat.hive.udf;
import java.util.Arrays;
import org.apache.hadoop.hive.ql.exec.UDF;
public final class SortFieldContent extends UDF {
        public String evaluate( final String str, String delimiter) {
               if (str == null ) {
                      return null ;
              }
               if (delimiter == null) {
                     delimiter = "," ;
              }
              String[] strs = str.split(delimiter);
              Arrays. sort(strs);
              String result = "" ;
               for (int i = 0; i < strs. length; i++) {
                      if (result.length() > 0) {
                           result.concat(delimiter);
                     }
                     result.concat(strs[i]);
              }
               return result;
       }

        public String evaluate( final String str, String delimiter, String order) {
               if (str == null ) {
                      return null ;
              }
               if (delimiter == null) {
                     delimiter = "," ;
              }
               if (order != null && order.toUpperCase().equals( "ASC" )) {
                      return evaluate(str, delimiter);
              } else {
                     String[] strs = str.split(delimiter);
                     Arrays. sort(strs);
                     String result = "" ;
                      for (int i = strs. length - 1; i >= 0; i--) {
                            if (result.length() > 0) {
                                  result.concat(delimiter);
                           }
                           result.concat(strs[i]);
                     }
                      return result;
              }
       }
}

UDAF步骤：

1.函数类继承org.apache.hadoop.hive.ql.exec.UDAF
内部类实现接口org.apache.hadoop.hive.ql.exec.UDAFEvaluator
2.Evaluator需要实现 init、iterate、terminatePartial、merge、terminate这几个函数
具体执行过程如图：

[java] view plain copy
package cn.sina.stat.hive.udaf;
import java.util.Arrays;
import org.apache.hadoop.hive.ql.exec.UDAF;
import org.apache.hadoop.hive.ql.exec.UDAFEvaluator;

public class ConcatClumnGroupByKeyWithOrder extends UDAF {
     public static class ConcatUDAFEvaluator implements UDAFEvaluator {
          public static class PartialResult {
               String result;
               String delimiter;
               String order;
          }

          private PartialResult partial;

          public void init() {
               partial = null;
          }

          public boolean iterate(String value, String delimiter, String order) {

               if (value == null) {
                    return true;
               }
               if (partial == null) {
                    partial = new PartialResult();
                    partial.result = new String("");
                    if (delimiter == null || delimiter.equals("")) {
                         partial.delimiter = new String(",");
                    } else {
                         partial.delimiter = new String(delimiter);
                    }
                    if (order != null
                              && (order.toUpperCase().equals("ASC") || order
                                        .toUpperCase().equals("DESC"))) {
                         partial.order = new String(order);
                    } else {
                         partial.order = new String("ASC");
                    }

               }
               if (partial.result.length() > 0) {
                    partial.result = partial.result.concat(partial.delimiter);
               }

               partial.result = partial.result.concat(value);

               return true;
          }

          public PartialResult terminatePartial() {
               return partial;
          }

          public boolean merge(PartialResult other) {
               if (other == null) {
                    return true;
               }
               if (partial == null) {
                    partial = new PartialResult();
                    partial.result = new String(other.result);
                    partial.delimiter = new String(other.delimiter);
                    partial.order = new String(other.order);
               } else {
                    if (partial.result.length() > 0) {
                         partial.result = partial.result.concat(partial.delimiter);
                    }
                    partial.result = partial.result.concat(other.result);
               }
               return true;
          }

          public String terminate() {
               String[] strs = partial.result.split(partial.delimiter);
               Arrays.sort(strs);
               String result = new String("");
               if (partial.order.equals("DESC")) {
                    for (int i = strs.length - 1; i >= 0; i--) {
                         if (result.length() > 0) {
                              result.concat(partial.delimiter);
                         }
                         result.concat(strs[i]);
                    }
               } else {
                    for (int i = 0; i < strs.length; i++) {
                         if (result.length() > 0) {
                              result.concat(partial.delimiter);
                         }
                         result.concat(strs[i]);
                    }
               }
               return new String(result);
          }
     }
}

UDTF步骤：

1.继承org.apache.hadoop.hive.ql.udf.generic.GenericUDTF
2.实现initialize, process, close三个方法
     a.initialize初始化验证，返回字段名和字段类型
     b.初始化完成后，调用process方法，对传入的参数进行处理，通过forword()方法把结果返回
     c.最后调用close()方法进行清理工作
[java] view plain copy
package cn.sina.stat.hive.udtf;
import java.util.ArrayList;
import java.util.Arrays;
import org.apache.hadoop.hive.ql.udf.generic.GenericUDTF;
import org.apache.hadoop.hive.ql.exec.UDFArgumentException;
import org.apache.hadoop.hive.ql.exec.UDFArgumentLengthException;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorFactory;
import org.apache.hadoop.hive.serde2.objectinspector.StructObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorFactory;

public class SortFieldExplodeToPair extends GenericUDTF {

     @Override
     public void close() throws HiveException {
          // TODO Auto-generated method stub
     }

     @Override
     public StructObjectInspector initialize(ObjectInspector[] args)
               throws UDFArgumentException {
          if (args.length != 3) {
               throw new UDFArgumentLengthException(
                         "SortFieldExplodeToPair takes only three argument");
          }
          if (args[0].getCategory() != ObjectInspector.Category.PRIMITIVE) {
               throw new UDFArgumentException(
                         "SortFieldExplodeToPair takes string as first parameter");
          }
          if (args[1].getCategory() != ObjectInspector.Category.PRIMITIVE) {
               throw new UDFArgumentException(
                         "SortFieldExplodeToPair takes string as second parameter");
          }
          if (args[2].getCategory() != ObjectInspector.Category.PRIMITIVE) {
               throw new UDFArgumentException(
                         "SortFieldExplodeToPair takes string as third parameter");
          }
          if (args[2] == null
                    || !(args[2].toString().toUpperCase().equals("ASC") || args[2]
                              .toString().toUpperCase().equals("DESC"))) {
               throw new UDFArgumentException(
                         "SortFieldExplodeToPair third parameter must be \"ASC\" or \"DESC\"");
          }

          ArrayList<String> fieldNames = new ArrayList<String>();
          ArrayList<ObjectInspector> fieldOIs = new ArrayList<ObjectInspector>();
          fieldNames.add("col1");
          fieldOIs.add(PrimitiveObjectInspectorFactory.javaStringObjectInspector);

          return ObjectInspectorFactory.getStandardStructObjectInspector(
                    fieldNames, fieldOIs);
     }

     private final String[] forwardStr = new String[1];

     @Override
     public void process(Object[] args) throws HiveException {
          String input = args[0].toString();
          String delimiter = args[1].toString();
          String order = args[2].toString();
          String[] strList = input.split(delimiter);
          Arrays.sort(strList);
          if (strList.length > 1) {
               if (order.toUpperCase().equals("DESC")) {
                    for (int i = strList.length - 1; i > 0; i--) {
                         forwardStr[0] = strList[i].concat(delimiter).concat(
                                   strList[i - 1]);
                         forward(forwardStr);
                    }
               } else {
                    for (int i = 0; i < strList.length - 1; i++) {
                         forwardStr[0] = strList[i].concat(delimiter).concat(
                                   strList[i + 1]);
                         forward(forwardStr);
                    }
               }
          } else {
               forward(strList);
          }
     }
}

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