[IMPALA-4176] Add batched bit-unpacking utility functions

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Impala 2.8.0
• Fix Version/s: Impala 2.8.0
• Component/s: Backend
• Target Version: Product Backlog
• Assignee: Tim Armstrong
• Reporter: Tim Armstrong
• Created: 21/Sep/16 17:18
• Updated: 20/Oct/16 16:04
• Resolved: 20/Oct/16 15:10

Description

To speed up parquet decoding we need fast bit unpacking functions, e.g. along the lines of https://github.com/lemire/FrameOfReference

Our current BitReader unpacks a value at a time and has a lot of unnecessary branches and other calculations.