| /* |
| * 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 org.apache.pig.EvalFunc; |
| import org.apache.pig.data.DataBag; |
| import org.apache.pig.data.DataType; |
| import org.apache.pig.data.NonSpillableDataBag; |
| 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; |
| import org.apache.pig.impl.logicalLayer.schema.Schema.FieldSchema; |
| |
| /** |
| * This class takes a list of items and puts them into a bag |
| * T = foreach U generate TOBAG($0, $1, $2); |
| * It's like saying this: |
| * T = foreach U generate {($0), ($1), ($2)} |
| * |
| * All arguments that are not of tuple type are inserted into a tuple before |
| * being added to the bag. This is because bag is always a bag of tuples. |
| * |
| * Output schema: |
| * The output schema for this udf depends on the schema of its arguments. |
| * If all the arguments have same type and same inner |
| * schema (for bags/tuple columns), then the udf output schema would be a bag |
| * of tuples having a column of the type and inner-schema (if any) of the |
| * arguments. |
| * If the arguments are of type tuple/bag, then their inner schemas should match, |
| * though schema field aliases may differ. |
| * If these conditions are not met the output schema will be a bag with null |
| * inner schema. |
| * |
| * example 1 |
| * grunt> describe a; |
| * a: {a0: int,a1: int} |
| * grunt> b = foreach a generate TOBAG(a0,a1); |
| * grunt> describe b; |
| * b: {{int}} |
| * |
| * example 2 |
| * grunt> describe a; |
| * a: {a0: (x: int),a1: (x: int)} |
| * grunt> b = foreach a generate TOBAG(a0,a1); |
| * grunt> describe b; |
| * b: {{(x: int)}} |
| * |
| * example 3 |
| * grunt> describe a; |
| * a: {a0: (x: int),a1: (y: int)} |
| * -- note that the inner schemas have matching types but different field aliases. |
| * -- the aliases of the first argument (a0) will be used in output schema: |
| * grunt> b = foreach a generate TOBAG(a0,a1); |
| * grunt> describe b; |
| * b: {{(x: int)}} |
| * |
| * example 4 |
| * grunt> describe a; |
| * a: {a0: (x: int),a1: (x: chararray)} |
| * -- here the inner schemas do not match, so output schema is not well defined: |
| * grunt> b = foreach a generate TOBAG(a0,a1); |
| * grunt> describe b; |
| * b: {{NULL}} |
| * |
| * |
| * |
| */ |
| public class TOBAG extends EvalFunc<DataBag> { |
| |
| @Override |
| public DataBag exec(Tuple input) throws IOException { |
| try { |
| // The assumption is that if the bag contents fits into |
| // an input tuple, it will not need to be spilled. |
| DataBag bag = new NonSpillableDataBag(input.size()); |
| |
| for (int i = 0; i < input.size(); ++i) { |
| final Object object = input.get(i); |
| if (object instanceof Tuple) { |
| bag.add( (Tuple) object); |
| } else { |
| Tuple tp2 = TupleFactory.getInstance().newTuple(1); |
| tp2.set(0, object); |
| bag.add(tp2); |
| } |
| } |
| |
| return bag; |
| } catch (Exception ee) { |
| throw new RuntimeException("Error while creating a bag", ee); |
| } |
| } |
| |
| /* (non-Javadoc) |
| * @see org.apache.pig.EvalFunc#outputSchema(org.apache.pig.impl.logicalLayer.schema.Schema) |
| * If all the columns in the tuple are of same type, then set the bag schema |
| * to bag of tuple with column of this type |
| * |
| */ |
| @Override |
| public Schema outputSchema(Schema inputSch) { |
| byte type = DataType.ERROR; |
| Schema innerSchema = null; |
| if(inputSch != null){ |
| for(FieldSchema fs : inputSch.getFields()){ |
| if(type == DataType.ERROR){ |
| type = fs.type; |
| innerSchema = fs.schema; |
| }else{ |
| if( type != fs.type || !nullEquals(innerSchema, fs.schema)){ |
| // invalidate the type |
| type = DataType.ERROR; |
| break; |
| } |
| } |
| } |
| } |
| try { |
| if(type == DataType.ERROR){ |
| return Schema.generateNestedSchema(DataType.BAG, DataType.NULL); |
| } |
| FieldSchema innerFs = new Schema.FieldSchema(null, innerSchema, type); |
| Schema innerSch = new Schema(innerFs); |
| Schema bagSchema = new Schema(new FieldSchema(null, innerSch, DataType.BAG)); |
| return bagSchema; |
| } catch (FrontendException e) { |
| //This should not happen |
| throw new RuntimeException("Bug : exception thrown while " + |
| "creating output schema for TOBAG udf", e); |
| } |
| |
| } |
| |
| private boolean nullEquals(Schema currentSchema, Schema newSchema) { |
| if(currentSchema == null){ |
| if(newSchema != null){ |
| return false; |
| } |
| return true; |
| } |
| return Schema.equals(currentSchema, newSchema, false, true); |
| } |
| |
| @Override |
| public boolean allowCompileTimeCalculation() { |
| return true; |
| } |
| } |
| |