Concurreny Model for Hive
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Key: HIVE-1293
URL: https://issues.apache.org/jira/browse/HIVE-1293
Project: Hadoop Hive
Issue Type: New Feature
Components: Query Processor
Reporter: Namit Jain
Concurrency model for Hive:
Currently, hive does not provide a good concurrency model. The only guanrantee
provided in case of concurrent readers and writers is that
reader will not see partial data from the old version (before the write) and
partial data from the new version (after the write).
This has come across as a big problem, specially for background processes
performing maintenance operations.
The following possible solutions come to mind.
1. Locks: Acquire read/write locks - they can be acquired at the beginning of
the query or the write locks can be delayed till move
task (when the directory is actually moved). Care needs to be taken for
deadlocks.
2. Versioning: The writer can create a new version if the current version is
being read. Note that, it is not equivalent to snapshots,
the old version can only be accessed by the current readers, and will be
deleted when all of them have finished.
Comments.
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