[IMPALA-3344] Simplify and document invariants in Sorter

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Impala 2.6.0
• Fix Version/s: Impala 2.7.0, Impala 2.6.2
• Component/s: Backend
• Labels: resource-management
• Target Version: Product Backlog, Impala 2.6.2
• Assignee: Tim Armstrong
• Reporter: Tim Armstrong
• Created: 13/Apr/16 17:43
• Updated: 08/Sep/16 16:28
• Resolved: 03/Jun/16 04:02

Description

The sorter code does not have its internal invariants well-documented and can be tricky to understand when working on it. E.g. what are the valid states for merged versus initial runs, how are end-of-block cases handled.

This issue is to clean up the sorter code while documenting important invariants as preparatory work for porting the sorter to the new buffer pool.