[HIVE-9401] Backport: Fastpath for limited fetches from unpartitioned tables

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 0.14.0, 0.15.0
• Fix Version/s: 1.0.0
• Component/s: Physical Optimizer
• Labels: Backport
• Release Note: SimpleFetchOptimizer for limited fetches without filters
• Assignee: Gopal Vijayaraghavan
• Reporter: Gopal Vijayaraghavan
• Created: 16/Jan/15 23:22
• Updated: 22/Jul/15 02:18
• Resolved: 21/Jan/15 01:51

Description

Currently, for flat tables, the threshold check is applicable for a query like select * from lineitem limit 1;.

This is not necessary as without a filter clause, this can be executed entirely via FetchTask. Running a cluster task is redundant for this case.

This fastpath is applicable for partitioned tables already.

Issue Links

• is a clone of: HIVE-9255 Fastpath for limited fetches from unpartitioned tables
• is required by: HIVE-10156 SimpleFetchOptimizer - disable all threshold check for an unfiltered select