| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.pig.builtin; |
| |
| import java.io.IOException; |
| import java.util.Iterator; |
| |
| import org.apache.pig.Accumulator; |
| import org.apache.pig.Algebraic; |
| import org.apache.pig.EvalFunc; |
| import org.apache.pig.PigException; |
| import org.apache.pig.backend.executionengine.ExecException; |
| import org.apache.pig.data.DataBag; |
| import org.apache.pig.data.DataType; |
| import org.apache.pig.data.Tuple; |
| import org.apache.pig.data.TupleFactory; |
| import org.apache.pig.impl.logicalLayer.schema.Schema; |
| |
| /** |
| * This method should never be used directly, use {@link MAX}. |
| */ |
| public class StringMax extends EvalFunc<String> implements Algebraic, Accumulator<String> { |
| |
| @Override |
| public String exec(Tuple input) throws IOException { |
| try { |
| return max(input); |
| } catch (ExecException ee) { |
| throw ee; |
| } |
| } |
| |
| @Override |
| public String getInitial() { |
| return Initial.class.getName(); |
| } |
| |
| @Override |
| public String getIntermed() { |
| return Intermediate.class.getName(); |
| } |
| |
| @Override |
| public String getFinal() { |
| return Final.class.getName(); |
| } |
| |
| static public class Initial extends EvalFunc<Tuple> { |
| private static TupleFactory tfact = TupleFactory.getInstance(); |
| |
| @Override |
| public Tuple exec(Tuple input) throws IOException { |
| try { |
| // input is a bag with one tuple containing |
| // the column we are trying to max on |
| DataBag bg = (DataBag) input.get(0); |
| String s = null; |
| if(bg.iterator().hasNext()) { |
| Tuple tp = bg.iterator().next(); |
| s = (String)(tp.get(0)); |
| } |
| return tfact.newTuple(s); |
| } catch (ExecException ee) { |
| throw ee; |
| } catch (Exception e) { |
| int errCode = 2106; |
| String msg = "Error while computing max in " + this.getClass().getSimpleName(); |
| throw new ExecException(msg, errCode, PigException.BUG, e); |
| } |
| } |
| } |
| |
| static public class Intermediate extends EvalFunc<Tuple> { |
| private static TupleFactory tfact = TupleFactory.getInstance(); |
| |
| @Override |
| public Tuple exec(Tuple input) throws IOException { |
| try { |
| return tfact.newTuple(max(input)); |
| } catch (ExecException ee) { |
| throw ee; |
| } catch (Exception e) { |
| int errCode = 2106; |
| String msg = "Error while computing max in " + this.getClass().getSimpleName(); |
| throw new ExecException(msg, errCode, PigException.BUG, e); |
| } |
| } |
| } |
| static public class Final extends EvalFunc<String> { |
| @Override |
| public String exec(Tuple input) throws IOException { |
| try { |
| return max(input); |
| } catch (ExecException ee) { |
| throw ee; |
| } catch (Exception e) { |
| int errCode = 2106; |
| String msg = "Error while computing max in " + this.getClass().getSimpleName(); |
| throw new ExecException(msg, errCode, PigException.BUG, e); |
| } |
| } |
| } |
| |
| static protected String max(Tuple input) throws ExecException { |
| DataBag values = (DataBag)input.get(0); |
| |
| // if we were handed an empty bag, return NULL |
| // this is in compliance with SQL standard |
| if(values == null || values.size() == 0) { |
| return null; |
| } |
| |
| Iterator<Tuple> it = values.iterator(); |
| // assign first non null element as max to begin with |
| String curMax = null; |
| while(curMax == null && it.hasNext()) { |
| Tuple t = it.next(); |
| curMax = (String)(t.get(0)); |
| } |
| |
| for (; it.hasNext();) { |
| Tuple t = it.next(); |
| try { |
| String s = (String)(t.get(0)); |
| if (s == null) continue; |
| if( s.compareTo(curMax) > 0) { |
| curMax = s; |
| } |
| |
| } catch (RuntimeException exp) { |
| int errCode = 2103; |
| String msg = "Problem while computing max of strings."; |
| throw new ExecException(msg, errCode, PigException.BUG, exp); |
| } |
| } |
| |
| return curMax; |
| } |
| |
| @Override |
| public Schema outputSchema(Schema input) { |
| return new Schema(new Schema.FieldSchema(null, DataType.CHARARRAY)); |
| } |
| |
| |
| /* accumulator interface */ |
| private String intermediateMax = null; |
| |
| @Override |
| public void accumulate(Tuple b) throws IOException { |
| try { |
| String curMax = max(b); |
| if (curMax == null) { |
| return; |
| } |
| // check if it lexicographically follows curMax |
| if (intermediateMax == null || intermediateMax.compareTo(curMax) < 0) { |
| intermediateMax = curMax; |
| } |
| |
| } catch (ExecException ee) { |
| throw ee; |
| } catch (Exception e) { |
| int errCode = 2106; |
| String msg = "Error while computing max in " + this.getClass().getSimpleName(); |
| throw new ExecException(msg, errCode, PigException.BUG, e); |
| } |
| } |
| |
| @Override |
| public void cleanup() { |
| intermediateMax = null; |
| } |
| |
| @Override |
| public String getValue() { |
| return intermediateMax; |
| } |
| } |