[DRILL-8290] Early exit from recursive file listing for LIMIT 0 queries

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.20.2
• Fix Version/s: 1.21.0
• Component/s: Query Planning & Optimization
• Assignee: James Turton
• Reporter: James Turton
• Created: 31/Aug/22 14:23
• Updated: 08/Feb/23 09:10
• Resolved: 08/Feb/23 09:10

Description

The existing LIMIT 0 query optimisations do not prevent a query run against the top of a deep DFS directory tree from recursively listing FileStatuses for everything within it using a pool of worker threads. This Issue proposes a new optimisation whereby such queries will recurse into the directory tree on a single thread that returns as soon as any single FileStatus has been obtained.