UDFArrayIntersect.java

package com.facebook.hive.udf;

import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDF;

import java.util.ArrayList;
import java.util.HashSet;

@Description(name = "udfarrayintersect",
             value = "_FUNC_(values) - Computes the intersection of the array arguments.  Note that ordering will be lost.")

  public class UDFArrayIntersect extends UDF {
    public ArrayList<String> evaluate(ArrayList<String>... arrays) {
      HashSet<String> result_set = null;

      for (int ii = 0; ii < arrays.length; ++ii) {
        if (arrays[ii] == null) {
          continue;
        }

        if (result_set == null) {
          result_set = new HashSet<String>(arrays[ii]);
        } else {
          result_set.retainAll(arrays[ii]);
        }
      }

      return new ArrayList<String>(result_set);
    }
  }