| /* |
| * 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; |
| |
| import java.io.IOException; |
| |
| import org.apache.hadoop.conf.Configuration; |
| |
| import org.apache.pig.classification.InterfaceAudience; |
| import org.apache.pig.classification.InterfaceStability; |
| import org.apache.pig.data.Tuple; |
| |
| /** |
| * This class is intended for use by LoadFunc implementations |
| * which have an internal index for sorted data and can use the index |
| * to support merge join in Pig. Interaction with the index |
| * is abstracted away by the methods in this interface which the Pig |
| * runtime will call in a particular sequence to get the records it |
| * needs to perform the merge based join. |
| * |
| * The sequence of calls made from the Pig runtime are: |
| * <ol> |
| * <li>{@link LoadFunc#setUDFContextSignature(String)} |
| * <li>{@link IndexableLoadFunc#initialize(Configuration)} |
| * <li>{@link LoadFunc#setLocation(String, org.apache.hadoop.mapreduce.Job)} |
| * <li>{@link IndexableLoadFunc#seekNear(Tuple)} |
| * <li>{@link LoadFunc#getNext} called multiple times to retrieve data and perform the join |
| * <li>{@link IndexableLoadFunc#close} |
| * </ol> |
| * @since Pig 0.6 |
| * |
| */ |
| @InterfaceAudience.Public |
| @InterfaceStability.Evolving // Set to evolving because we don't have this working with outer join |
| // yet, and we may need to change it some for that. |
| public interface IndexableLoadFunc { |
| |
| /** |
| * This method is called by Pig run time to allow the |
| * IndexableLoadFunc to perform any initialization actions |
| * @param conf The job configuration object |
| * @throws IOException |
| */ |
| public abstract void initialize(Configuration conf) throws IOException; |
| |
| /** |
| * This method is called by the Pig runtime to indicate |
| * to the LoadFunc to position its underlying input stream |
| * near the keys supplied as the argument. Specifically: |
| * 1) if the keys are present in the input stream, the loadfunc |
| * implementation should position its read position to |
| * a record where the key(s) is/are the biggest key(s) less than |
| * the key(s) supplied in the argument OR to the record with the |
| * first occurrence of the keys(s) supplied. |
| * 2) if the key(s) are absent in the input stream, the implementation |
| * should position its read position to a record where the key(s) |
| * is/are the biggest key(s) less than the key(s) supplied OR to the |
| * first record where the key(s) is/are the smallest key(s) greater |
| * than the keys(s) supplied. |
| * The description above holds for descending order data in |
| * a similar manner with "biggest" and "less than" replaced with |
| * "smallest" and "greater than" and vice versa. |
| * |
| * @param keys Tuple with join keys (which are a prefix of the sort |
| * keys of the input data). For example if the data is sorted on |
| * columns in position 2,4,5 any of the following Tuples are |
| * valid as an argument value: |
| * (fieldAt(2)) |
| * (fieldAt(2), fieldAt(4)) |
| * (fieldAt(2), fieldAt(4), fieldAt(5)) |
| * |
| * The following are some invalid cases: |
| * (fieldAt(4)) |
| * (fieldAt(2), fieldAt(5)) |
| * (fieldAt(4), fieldAt(5)) |
| * |
| * @throws IOException When the loadFunc is unable to position |
| * to the required point in its input stream |
| */ |
| public abstract void seekNear(Tuple keys) throws IOException; |
| |
| |
| /** |
| * A method called by the Pig runtime to give an opportunity |
| * for implementations to perform cleanup actions like closing |
| * the underlying input stream. This is necessary since while |
| * performing a join the Pig run time may determine than no further |
| * join is possible with remaining records and may indicate to the |
| * IndexableLoader to cleanup by calling this method. |
| * |
| * @throws IOException if the loadfunc is unable to perform |
| * its close actions. |
| */ |
| public abstract void close() throws IOException; |
| } |