Ngone51 commented on a change in pull request #29000:
URL: https://github.com/apache/spark/pull/29000#discussion_r464917882
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File path:
core/src/main/scala/org/apache/spark/internal/io/HadoopMapReduceCommitProtocol.scala
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@@ -41,13 +41,23 @@ import org.apache.spark.mapred.SparkHadoopMapRedUtil
* @param jobId the job's or stage's id
* @param path the job's output path, or null if committer acts as a noop
* @param dynamicPartitionOverwrite If true, Spark will overwrite partition
directories at runtime
- * dynamically, i.e., we first write files
under a staging
- * directory with partition path, e.g.
- * /path/to/staging/a=1/b=1/xxx.parquet. When
committing the job,
- * we first clean up the corresponding
partition directories at
- * destination path, e.g.
/path/to/destination/a=1/b=1, and move
- * files from staging directory to the
corresponding partition
- * directories under destination path.
+ * dynamically, i.e., we first write files to
task attempt paths
+ * under a staging directory, e.g.
+ *
/path/to/outputPath/.spark-staging-{jobId}/_temporary/
+ *
{appAttemptId}/_temporary/{taskAttemptId}/a=1/b=1/xxx.parquet.
+ * 1. When [[FileOutputCommitter]] algorithm
version set to 1,
+ * we firstly move files from task attempt
+ * paths to corresponding partition
directories under the staging
+ * directory during committing job, e.g.
+ *
/path/to/outputPath/.spark-staging-{jobId}/a=1/b=1.
+ * Secondly, move the partition directories
under staging
+ * directory to destination path, e.g.
/path/to/outputPath/a=1/b=1
+ * 2. When [[FileOutputCommitter]] algorithm
version set to 2,
+ * committing tasks directly move files to
staging directory,
+ * e.g.
/path/to/outputPath/.spark-staging-{jobId}/a=1/b=1.
+ * Then move this partition directories under
staging directory
+ * to destination path during job committing,
e.g.
+ * /path/to/outputPath/a=1/b=1
Review comment:
Thanks for your detailed explanation. But since these are underlying
details rather than implemented by Spark, I think it's better to simplify it.
e.g., we first..., then move ... from ... to... and move to ... at the end.
WDYT?
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