Resolution: Won't Fix
Affects Version/s: 2.1.0
Fix Version/s: None
Hive's MoveTask uses the Hive.moveFile method to move data within a distributed filesystem as well as blobstore filesystems.
If the move is done within the same filesystem:
1: If the source path is a subdirectory of the destination path, files will be moved one by one using a threapool of workers
2: If the source path is not a subdirectory of the destination path, a single rename operation is used to move the entire directory
The second option may not work well on blobstores such as S3. Renames are not metadata operations and require copying all the data. Client connectors to blobstores may not efficiently rename directories. Worst case, the connector will copy each file one by one, sequentially rather than using a threadpool of workers to copy the data (e.g.
Hive already has code to rename files using a threadpool of workers, but this only occurs in case number 1.
This JIRA aims to modify the code so that case 1 is triggered when copying within a blobstore. The focus is on copies within a blobstore because needToCopy will return true if the src and target filesystems are different, in which case a different code path is triggered.