| /* |
| * 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.Serializable; |
| import java.util.ArrayList; |
| import java.util.List; |
| |
| import org.apache.pig.classification.InterfaceAudience; |
| import org.apache.pig.classification.InterfaceStability; |
| import org.apache.pig.impl.logicalLayer.FrontendException; |
| |
| /** |
| * This interface defines how to communicate to Pig what functionality can |
| * be pushed into the loader. If a given loader does not implement this interface |
| * it will be assumed that it is unable to accept any functionality for push down. |
| * @since Pig 0.7 |
| */ |
| @InterfaceAudience.Public |
| @InterfaceStability.Evolving |
| public interface LoadPushDown { |
| |
| /** |
| * Set of possible operations that Pig can push down to a loader. |
| */ |
| enum OperatorSet {PROJECTION}; |
| |
| /** |
| * Determine the operators that can be pushed to the loader. |
| * Note that by indicating a loader can accept a certain operator |
| * (such as selection) the loader is not promising that it can handle |
| * all selections. When it is passed the actual operators to |
| * push down it will still have a chance to reject them. |
| * @return list of all features that the loader can support |
| */ |
| List<OperatorSet> getFeatures(); |
| |
| /** |
| * Indicate to the loader fields that will be needed. This can be useful for |
| * loaders that access data that is stored in a columnar format where indicating |
| * columns to be accessed a head of time will save scans. This method will |
| * not be invoked by the Pig runtime if all fields are required. So implementations |
| * should assume that if this method is not invoked, then all fields from |
| * the input are required. If the loader function cannot make use of this |
| * information, it is free to ignore it by returning an appropriate Response |
| * @param requiredFieldList RequiredFieldList indicating which columns will be needed. |
| * This structure is read only. User cannot make change to it inside pushProjection. |
| * @return Indicates which fields will be returned |
| * @throws FrontendException |
| */ |
| public RequiredFieldResponse pushProjection(RequiredFieldList |
| requiredFieldList) throws FrontendException; |
| |
| /** |
| * Describes a field that is required to execute a scripts. |
| */ |
| @InterfaceAudience.Public |
| @InterfaceStability.Evolving |
| public static class RequiredField implements Serializable { |
| |
| private static final long serialVersionUID = 1L; |
| |
| // will hold name of the field (would be null if not supplied) |
| private String alias; |
| |
| // will hold the index (position) of the required field (would be -1 if not supplied), index is 0 based |
| private int index; |
| |
| // A list of sub fields in this field (this could be a list of hash keys for example). |
| // This would be null if the entire field is required and no specific sub fields are required. |
| // In the initial implementation only one level of subfields will be populated. |
| private List<RequiredField> subFields; |
| |
| // Type of this field - the value could be any current PIG DataType (as specified by the constants in DataType class). |
| private byte type; |
| |
| public RequiredField() { |
| // to allow piece-meal construction |
| } |
| |
| /** |
| * @param alias |
| * @param index |
| * @param subFields |
| * @param type |
| */ |
| public RequiredField(String alias, int index, |
| List<RequiredField> subFields, byte type) { |
| this.alias = alias; |
| this.index = index; |
| this.subFields = subFields; |
| this.type = type; |
| } |
| |
| /** |
| * @return the alias |
| */ |
| public String getAlias() { |
| return alias; |
| } |
| |
| /** |
| * @return the index |
| */ |
| public int getIndex() { |
| return index; |
| } |
| |
| |
| /** |
| * @return the required sub fields. The return value is null if all |
| * subfields are required |
| */ |
| public List<RequiredField> getSubFields() { |
| return subFields; |
| } |
| |
| public void setSubFields(List<RequiredField> subFields) |
| { |
| this.subFields = subFields; |
| } |
| |
| /** |
| * @return the type |
| */ |
| public byte getType() { |
| return type; |
| } |
| |
| public void setType(byte t) { |
| type = t; |
| } |
| |
| public void setIndex(int i) { |
| index = i; |
| } |
| |
| public void setAlias(String alias) |
| { |
| this.alias = alias; |
| } |
| |
| @Override |
| public String toString() { |
| if (index != -1) |
| return "" + index; |
| else if (alias != null) |
| return alias; |
| return ""; |
| } |
| } |
| |
| /** |
| * List of fields that Pig knows to be required to executed a script. |
| */ |
| @InterfaceAudience.Public |
| @InterfaceStability.Evolving |
| public static class RequiredFieldList implements Serializable { |
| |
| private static final long serialVersionUID = 1L; |
| |
| // list of Required fields, this will be null if all fields are required |
| private List<RequiredField> fields = new ArrayList<RequiredField>(); |
| |
| /** |
| * Set the list of required fields. |
| * @param fields |
| */ |
| public RequiredFieldList(List<RequiredField> fields) { |
| this.fields = fields; |
| } |
| |
| /** |
| * Geta ll required fields as a list. |
| * @return the required fields - this will be null if all fields are |
| * required |
| */ |
| public List<RequiredField> getFields() { |
| return fields; |
| } |
| |
| public RequiredFieldList() { |
| } |
| |
| @Override |
| public String toString() { |
| StringBuffer result = new StringBuffer(); |
| if (fields == null) |
| result.append("*"); |
| else { |
| result.append("["); |
| for (int i = 0; i < fields.size(); i++) { |
| result.append(fields.get(i)); |
| if (i != fields.size() - 1) |
| result.append(","); |
| } |
| result.append("]"); |
| } |
| return result.toString(); |
| } |
| |
| /** |
| * Add a field to the list of required fields. |
| * @param rf required field to add to the list. |
| */ |
| public void add(RequiredField rf) |
| { |
| fields.add(rf); |
| } |
| } |
| |
| /** |
| * Indicates whether the loader will return the requested fields or all fields. |
| */ |
| @InterfaceAudience.Public |
| @InterfaceStability.Evolving |
| public static class RequiredFieldResponse { |
| // the loader should pass true if it will return data containing |
| // only the List of RequiredFields in that order. false if it |
| // will return all fields in the data |
| private boolean requiredFieldRequestHonored; |
| |
| public RequiredFieldResponse(boolean requiredFieldRequestHonored) { |
| this.requiredFieldRequestHonored = requiredFieldRequestHonored; |
| } |
| |
| /** |
| * Indicates whether the loader will return only the requested fields or all fields. |
| * @return true if only requested fields will be returned, false if all fields will be |
| * returned. |
| */ |
| public boolean getRequiredFieldResponse() { |
| return requiredFieldRequestHonored; |
| } |
| |
| /** |
| * Set whether the loader will return only the requesetd fields or all fields. |
| * @param honored if true only requested fields will be returned, else all fields will be |
| * returned. |
| */ |
| public void setRequiredFieldResponse(boolean honored) { |
| requiredFieldRequestHonored = honored; |
| } |
| } |
| |
| |
| } |