| /* |
| * 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.tutorial; |
| |
| import java.io.IOException; |
| import java.util.ArrayList; |
| import java.util.HashSet; |
| import java.util.List; |
| import java.util.Set; |
| |
| import org.apache.pig.EvalFunc; |
| import org.apache.pig.FuncSpec; |
| import org.apache.pig.data.DataBag; |
| import org.apache.pig.data.DataType; |
| import org.apache.pig.data.DefaultBagFactory; |
| import org.apache.pig.data.Tuple; |
| import org.apache.pig.data.TupleFactory; |
| import org.apache.pig.impl.logicalLayer.FrontendException; |
| import org.apache.pig.impl.logicalLayer.schema.Schema; |
| |
| /** |
| * This function divides a search query string into wrods and extracts |
| * n-grams with up to _ngramSizeLimit length. |
| * Example 1: if query = "a real nice query" and _ngramSizeLimit = 2, |
| * the query is split into: a, real, nice, query, a real, real nice, nice query |
| * Example 2: if record = (u1, h1, pig hadoop) and _ngramSizeLimit = 2, |
| * the record is split into: (u1, h1, pig), (u1, h1, hadoop), (u1, h1, pig hadoop) |
| */ |
| public class NGramGenerator extends EvalFunc<DataBag> { |
| |
| private static final int _ngramSizeLimit = 2; |
| |
| public DataBag exec(Tuple input) throws IOException { |
| if (input == null || input.size() == 0) |
| return null; |
| try{ |
| DataBag output = DefaultBagFactory.getInstance().newDefaultBag(); |
| String query = (String)input.get(0); |
| String[] words = TutorialUtil.splitToWords(query); |
| Set<String> ngrams = new HashSet<String>(); |
| TutorialUtil.makeNGram(words, ngrams, _ngramSizeLimit); |
| for (String ngram : ngrams) { |
| Tuple t = TupleFactory.getInstance().newTuple(1); |
| t.set(0, ngram); |
| output.add(t); |
| } |
| return output; |
| }catch(Exception e){ |
| System.err.println("NGramGenerator: failed to process input; error - " + e.getMessage()); |
| return null; |
| } |
| } |
| |
| @Override |
| /** |
| * This method gives a name to the column. |
| * @param input - schema of the input data |
| * @return schema of the input data |
| */ |
| public Schema outputSchema(Schema input) { |
| Schema bagSchema = new Schema(); |
| bagSchema.add(new Schema.FieldSchema("ngram", DataType.CHARARRAY)); |
| try{ |
| return new Schema(new Schema.FieldSchema(getSchemaName(this.getClass().getName().toLowerCase(), input), |
| bagSchema, DataType.BAG)); |
| }catch (FrontendException e){ |
| return null; |
| } |
| } |
| |
| /* (non-Javadoc) |
| * @see org.apache.pig.EvalFunc#getArgToFuncMapping() |
| * This is needed to make sure that both bytearrays and chararrays can be passed as arguments |
| */ |
| @Override |
| public List<FuncSpec> getArgToFuncMapping() throws FrontendException { |
| List<FuncSpec> funcList = new ArrayList<FuncSpec>(); |
| funcList.add(new FuncSpec(this.getClass().getName(), new Schema(new Schema.FieldSchema(null, DataType.CHARARRAY)))); |
| |
| return funcList; |
| } |
| |
| } |