[HIVE-12049] HiveServer2: Provide an option to write serialized thrift objects in final tasks

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.0.0
• Fix Version/s: 2.1.0
• Component/s: HiveServer2, JDBC
• Labels: TODOC2.1
• Target Version/s: 2.1.0
• Hadoop Flags: Reviewed
• Assignee: Rohit Dholakia
• Reporter: Rohit Dholakia
• Created: 06/Oct/15 20:55
• Updated: 14/Oct/16 06:32
• Resolved: 22/Apr/16 19:24

Description

For each fetch request to HiveServer2, we pay the penalty of deserializing the row objects and translating them into a different representation suitable for the RPC transfer. In a moderate to high concurrency scenarios, this can result in significant CPU and memory wastage. By having each task write the appropriate thrift objects to the output files, HiveServer2 can simply stream a batch of rows on the wire without incurring any of the additional cost of deserialization and translation.
This can be implemented by writing a new SerDe, which the FileSinkOperator can use to write thrift formatted row batches to the output file. Using the pluggable property of the hive.query.result.fileformat, we can set it to use SequenceFile and write a batch of thrift formatted rows as a value blob. The FetchTask can now simply read the blob and send it over the wire. On the client side, the *DBC driver can read the blob and since it is already formatted in the way it expects, it can continue building the ResultSet the way it does in the current implementation.

Issue Links

• blocks: HIVE-12428 HiveServer2: Provide an option for HiveServer2 to stream serialized thrift results when they are available
• is related to: HIVE-10438 HiveServer2: Enable Type specific ResultSet compression
• is related to: HIVE-14876 make the number of rows to fetch from various HS2 clients/servers configurable
• links to: Review Board - Rohit
• links to: Review Board - Vaibhav