| /* |
| * 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 java.util.List; |
| |
| import org.apache.hadoop.mapreduce.Job; |
| import org.apache.pig.classification.InterfaceAudience; |
| import org.apache.pig.classification.InterfaceStability; |
| |
| /** |
| * This interface defines how a loader can support predicate pushdown. |
| * If a given loader implements this interface, pig will pushdown predicates based on |
| * type of operations supported by the loader on given set of fields. |
| * |
| * This interface is private in Pig 0.14 and will be made public in Pig 0.15 after PIG-4093. |
| * It is to be used only by builtin LoadFunc implementations till it is made public |
| * as PIG-4093 will cause API changes to this interface and make it backward incompatible. |
| * |
| * @since Pig 0.14 |
| */ |
| @InterfaceAudience.Private |
| @InterfaceStability.Evolving |
| public interface LoadPredicatePushdown { |
| /** |
| * Find what fields of the data can support predicate pushdown. |
| * @param location Location as returned by |
| * {@link LoadFunc#relativeToAbsolutePath(String, org.apache.hadoop.fs.Path)} |
| * |
| * @param job The {@link Job} object - this should be used only to obtain |
| * cluster properties through {@link Job#getConfiguration()} and not to set/query |
| * any runtime job information. |
| * |
| * @return list of field names that can be pushed down. Implementations |
| * should return null to indicate that there are no fields that support predicate pushdown |
| * |
| * @throws IOException if an exception occurs while retrieving predicate fields |
| */ |
| List<String> getPredicateFields(String location, Job job) |
| throws IOException; |
| |
| /** |
| * Indicate operations on fields supported by the loader for predicate pushdown |
| * |
| * @return List of operations supported by the predicate pushdown loader |
| */ |
| List<Expression.OpType> getSupportedExpressionTypes(); |
| |
| /** |
| * Push down expression to the loader |
| * |
| * @param predicate expression to be filtered by the loader. |
| * @throws IOException |
| */ |
| void setPushdownPredicate(Expression predicate) throws IOException; |
| |
| } |
| |