hive基于UDAF的编写

-------------
select concat(account,'\t',bfdutmb,'\t',page_url) from (
select account,bfdutmb,actionPath(page_url,'->') page_url from (
select create_time,account,bfdutmb,page_url page_url from ods_action_event
order by account,bfdutmb,create_time)c
group by account,bfdutmb)b 

 

import org.apache.hadoop.hive.ql.exec.UDAF;
import org.apache.hadoop.hive.ql.exec.UDAFEvaluator;

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

		private PartialResult partial;

		public void init() {
			partial = null;
		}

		public boolean iterate(String value, String deli) {

			if (value == null) {
				return true;
			}
			if (partial == null) {
				partial = new PartialResult();
				partial.result = new String("");
				if (deli == null || deli.equals("")) {
					partial.delimiter = new String(",");
				} else {
					partial.delimiter = new String(deli);
				}

			}
			if (partial.result.length() > 0) {
				partial.result = partial.result.concat(partial.delimiter);//result='aa',delimiter='->' | aa->
			}

			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);
			} 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() {
			return new String(partial.result);
		}
	}
}