Apache Pig Explain运算符

由 jarodhu 创建，youj 最后一次修改 2016-12-28 explain 运算符用于显示关系的逻辑，物理和MapReduce执行计划。语法下面给出了 explain 运算符的语法。grunt> explain Relation_name;例假设在HDFS中有一个包含以下内容的文件 student_data.txt 。001,Rajiv,Reddy,9848022337,Hyderabad002,siddarth,Battacharya,9848022338,Kolkata003,Rajesh,Khanna,9848022339,Delhi004,Preethi,Agarwal,9848022330,Pune005,Trupthi,Mohanthy,9848022336,Bhuwaneshwar006,Archana,Mishra,9848022335,Chennai.使用LOAD运算符将它读入关系 student ，如下所示。grunt> student = LOAD 'hdfs://localhost:9000/pig_data/student_data.txt' USING PigStorage(',') as ( id:int, firstname:chararray, lastname:chararray, phone:chararray, city:chararray );现在，让我们使用 explain 运算符解释名为student的关系，如下所示。grunt> explain student;输出它将产生以下输出。$ explain student;2015-10-05 11:32:43,660 [main]2015-10-05 11:32:43,660 [main] INFO org.apache.pig.newplan.logical.optimizer.LogicalPlanOptimizer -{RULES_ENABLED=[AddForEach, ColumnMapKeyPrune, ConstantCalculator,GroupByConstParallelSetter, LimitOptimizer, LoadTypeCastInserter, MergeFilter, MergeForEach, PartitionFilterOptimizer, PredicatePushdownOptimizer,PushDownForEachFlatten, PushUpFilter, SplitFilter, StreamTypeCastInserter]} #-----------------------------------------------# New Logical Plan: #-----------------------------------------------student: (Name: LOStore Schema:id#31:int,firstname#32:chararray,lastname#33:chararray,phone#34:chararray,city#35:chararray)| |---student: (Name: LOForEach Schema:id#31:int,firstname#32:chararray,lastname#33:chararray,phone#34:chararray,city#35:chararray) | | | (Name: LOGenerate[false,false,false,false,false] Schema:id#31:int,firstname#32:chararray,lastname#33:chararray,phone#34:chararray,city#35:chararray)ColumnPrune:InputUids=[34, 35, 32, 33,31]ColumnPrune:OutputUids=[34, 35, 32, 33, 31] | | | | | (Name: Cast Type: int Uid: 31) | | | | | |---id:(Name: Project Type: bytearray Uid: 31 Input: 0 Column: (*)) | | | | | (Name: Cast Type: chararray Uid: 32) | | | | | |---firstname:(Name: Project Type: bytearray Uid: 32 Input: 1Column: (*)) | | | | | (Name: Cast Type: chararray Uid: 33) | | | | | |---lastname:(Name: Project Type: bytearray Uid: 33 Input: 2 Column: (*)) | | | | | (Name: Cast Type: chararray Uid: 34) | | | | | |---phone:(Name: Project Type: bytearray Uid: 34 Input: 3 Column:(*)) | | | | | (Name: Cast Type: chararray Uid: 35) | | | | | |---city:(Name: Project Type: bytearray Uid: 35 Input: 4 Column:(*)) | | | |---(Name: LOInnerLoad[0] Schema: id#31:bytearray) | | | |---(Name: LOInnerLoad[1] Schema: firstname#32:bytearray) | | | |---(Name: LOInnerLoad[2] Schema: lastname#33:bytearray) | | | |---(Name: LOInnerLoad[3] Schema: phone#34:bytearray) | | | |---(Name: LOInnerLoad[4] Schema: city#35:bytearray) | |---student: (Name: LOLoad Schema: id#31:bytearray,firstname#32:bytearray,lastname#33:bytearray,phone#34:bytearray,city#35:bytearray)RequiredFields:null #-----------------------------------------------# Physical Plan: #-----------------------------------------------student: Store(fakefile:org.apache.pig.builtin.PigStorage) - scope-36| |---student: New For Each(false,false,false,false,false)[bag] - scope-35 | | | Cast[int] - scope-21 | | | |---Project[bytearray][0] - scope-20 | | | Cast[chararray] - scope-24 | | | |---Project[bytearray][1] - scope-23 | | | Cast[chararray] - scope-27 | | | |---Project[bytearray][2] - scope-26 | | | Cast[chararray] - scope-30 | | | |---Project[bytearray][3] - scope-29 | | | Cast[chararray] - scope-33 | | | |---Project[bytearray][4] - scope-32 | |---student: Load(hdfs://localhost:9000/pig_data/student_data.txt:PigStorage(',')) - scope192015-10-05 11:32:43,682 [main]INFO org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.MRCompiler - File concatenation threshold: 100 optimistic? false2015-10-05 11:32:43,684 [main]INFO org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.MultiQueryOp timizer - MR plan size before optimization: 1 2015-10-05 11:32:43,685 [main]INFO org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.MultiQueryOp timizer - MR plan size after optimization: 1 #--------------------------------------------------# Map Reduce Plan #--------------------------------------------------MapReduce node scope-37Map Planstudent: Store(fakefile:org.apache.pig.builtin.PigStorage) - scope-36||---student: New For Each(false,false,false,false,false)[bag] - scope-35 | | | Cast[int] - scope-21 | | | |---Project[bytearray][0] - scope-20 | | | Cast[chararray] - scope-24 | | | |---Project[bytearray][1] - sco