我们正在尝试读取一个大的配置单元表，该表是rcfile格式的。它正在逐个处理表的所有分区。到目前为止，map任务似乎已经编写了30个溢出文件。
有一次，它开始处理一个文件，下面是日志，

2018-06-15 00:54:28,977 INFO org.apache.hadoop.hive.ql.io.HiveContextAwareRecordReader: Processing file hdfs://xxx:8020/data/csv/7342/2018-06-14/17/1/Network_xxx.dat
2018-06-15 00:54:29,005 INFO org.apache.hadoop.hive.ql.exec.MapOperator: Processing alias ntwk for file hdfs://xxx:8020/data/csv/7342/2018-06-14/17/1
2018-06-15 00:55:04,029 INFO org.apache.hadoop.hive.ql.exec.MapOperator: 7 finished. closing... 
2018-06-15 00:55:04,129 INFO org.apache.hadoop.hive.ql.exec.MapOperator: 7 forwarded 6672342 rows
2018-06-15 00:55:04,266 INFO org.apache.hadoop.hive.ql.exec.TableScanOperator: 3 finished. closing... 
2018-06-15 00:55:04,266 INFO org.apache.hadoop.hive.ql.exec.TableScanOperator: 3 forwarded 0 rows
2018-06-15 00:55:04,513 INFO org.apache.hadoop.hive.ql.exec.ReduceSinkOperator: 2 finished. closing... 
2018-06-15 00:55:04,538 INFO org.apache.hadoop.hive.ql.exec.ReduceSinkOperator: 2 forwarded 0 rows
2018-06-15 00:55:04,563 INFO org.apache.hadoop.hive.ql.exec.TableScanOperator: 3 Close done
2018-06-15 00:55:04,589 INFO org.apache.hadoop.hive.ql.exec.MapOperator: DESERIALIZE_ERRORS:0
2018-06-15 00:55:04,616 INFO org.apache.hadoop.hive.ql.exec.TableScanOperator: 1 finished. closing... 
2018-06-15 00:55:04,641 INFO org.apache.hadoop.hive.ql.exec.TableScanOperator: 1 forwarded 6672342 rows
2018-06-15 00:55:04,666 INFO org.apache.hadoop.hive.ql.exec.ReduceSinkOperator: 0 finished. closing... 
2018-06-15 00:55:04,691 INFO org.apache.hadoop.hive.ql.exec.ReduceSinkOperator: 0 forwarded 0 rows
2018-06-15 00:55:04,716 INFO org.apache.hadoop.hive.ql.exec.TableScanOperator: 1 Close done
2018-06-15 00:55:04,741 INFO org.apache.hadoop.hive.ql.exec.MapOperator: 7 Close done
2018-06-15 00:55:04,792 INFO ExecMapper: ExecMapper: processed 6672342 rows: used memory = 412446808
2018-06-15 00:55:10,316 INFO org.apache.hadoop.mapred.TaskLogsTruncater: Initializing logs' truncater with mapRetainSize=-1 and reduceRetainSize=-1
2018-06-15 00:55:10,852 FATAL org.apache.hadoop.mapred.Child: Error running child : java.lang.OutOfMemoryError: Java heap space
    at org.apache.hadoop.io.compress.DecompressorStream.<init>(DecompressorStream.java:50)
    at org.apache.hadoop.io.compress.BlockDecompressorStream.<init>(BlockDecompressorStream.java:50)
    at org.apache.hadoop.io.compress.SnappyCodec.createInputStream(SnappyCodec.java:173)
    at org.apache.hadoop.hive.ql.io.RCFile$Reader.nextKeyBuffer(RCFile.java:1447)
    at org.apache.hadoop.hive.ql.io.RCFile$Reader.next(RCFile.java:1602)
    at org.apache.hadoop.hive.ql.io.RCFileRecordReader.next(RCFileRecordReader.java:98)
    at org.apache.hadoop.hive.ql.io.RCFileRecordReader.next(RCFileRecordReader.java:85)
    at org.apache.hadoop.hive.ql.io.RCFileRecordReader.next(RCFileRecordReader.java:39)
    at org.apache.hadoop.hive.ql.io.HiveContextAwareRecordReader.doNext(HiveContextAwareRecordReader.java:274)
    at org.apache.hadoop.hive.ql.io.CombineHiveRecordReader.doNext(CombineHiveRecordReader.java:101)
    at org.apache.hadoop.hive.ql.io.CombineHiveRecordReader.doNext(CombineHiveRecordReader.java:41)
    at org.apache.hadoop.hive.ql.io.HiveContextAwareRecordReader.next(HiveContextAwareRecordReader.java:108)
    at org.apache.hadoop.hive.shims.HadoopShimsSecure$CombineFileRecordReader.doNextWithExceptionHandler(HadoopShimsSecure.java:329)
    at org.apache.hadoop.hive.shims.HadoopShimsSecure$CombineFileRecordReader.next(HadoopShimsSecure.java:247)
    at org.apache.hadoop.mapred.MapTask$TrackedRecordReader.moveToNext(MapTask.java:215)
    at org.apache.hadoop.mapred.MapTask$TrackedRecordReader.next(MapTask.java:200)
    at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:48)
    at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:417)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:332)
    at org.apache.hadoop.mapred.Child$4.run(Child.java:268)
    at java.security.AccessController.doPrivileged(Native Method)
    at javax.security.auth.Subject.doAs(Subject.java:415)
    at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1408)
    at org.apache.hadoop.mapred.Child.main(Child.java:262)

它是如何处理其他文件的，以及为什么在这个时候出现outofmemory错误。内部会发生什么？
Map任务中的堆空间和Map缓冲区有什么区别？
以下是一些配置：

mapred.map.child.java.opts : -Xmx512M
mapred.job.reduce.memory.mb : -1
mapred.job.map.memory.mb : -1

配置单元Map任务也已开始打印统计信息、已处理的行数和已使用的内存。使用的内存似乎远低于配置的内存。
为什么6秒后打印的统计数据，它已注册outofmemory错误。我不明白会出什么问题。

**2018-06-15 00:55:04,741 INFO org.apache.hadoop.hive.ql.exec.MapOperator: 7 Close done

2018-06-15 00:55:04,792**INFO ExecMapper: ExecMapper: processed 6672342 rows: used memory = 412446808**
2018-06-15 00:55:10,316 INFO org.apache.hadoop.mapred.TaskLogsTruncater: Initializing logs' truncater with mapRetainSize=-1 and reduceRetainSize=-1
2018-06-15 00:55:10,852**FATAL org.apache.hadoop.mapred.Child: Error running child : java.lang.OutOfMemoryError: Java heap space**
    at org.apache.hadoop.io.compress.DecompressorStream.<init>(DecompressorStream.java:50)
    at org.apache.hadoop.io.compress.BlockDecompressorStream.<init>(BlockDecompressorStream.java:50)
    at org.apache.hadoop.io.compress.SnappyCodec.createInputStream(SnappyCodec.java:173)
    at org.apache.hadoop.hive.ql.io.RCFile$Reader.nextKeyBuffer(RCFile.java:1447)**