[HIVE-19985] ACID: Skip decoding the ROW__ID sections for read-only queries

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.0.0
• Fix Version/s: 4.0.0-alpha-1
• Component/s: Transactions
• Labels: Branch3Candidate
• Target Version/s: 4.0.0
• Assignee: Eugene Koifman
• Reporter: Gopal Vijayaraghavan
• Created: 25/Jun/18 20:19
• Updated: 27/Feb/24 22:23
• Resolved: 29/Sep/18 16:58

Description

For a base_n file there are no aborted transactions within the file and if there are no pending delete deltas, the entire ACID ROW__ID can be skipped for all read-only queries (i.e SELECT), though it still needs to be projected out for MERGE, UPDATE and DELETE queries.

This patch tries to entirely ignore the ACID ROW__ID fields for all tables where there are no possible deletes or aborted transactions for an ACID split.

Issue Links

• blocks: HIVE-20654 remove masking of "Masked writeid"
• is blocked by: HIVE-20418 LLAP IO may not handle ORC files that have row index disabled correctly for queries with no columns selected
• is related to: HIVE-16812 VectorizedOrcAcidRowBatchReader doesn't filter delete events
• is related to: HIVE-19890 ACID: Inherit bucket-id from original ROW_ID for delete deltas
• is required by: HIVE-20655 Optimize arrayCopy in LlapRecordReader
• requires: HIVE-20640 Upgrade Hive to use ORC 1.5.3
• requires: ORC-389 Add ability to not decode Acid metadata columns