[DRILL-8088] Improve expression evaluation performance

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.19.0
• Fix Version/s: 1.20.0
• Component/s: Execution - Codegen
• Assignee: wtf
• Reporter: wtf
• Created: 20/Dec/21 15:15
• Updated: 12/Jul/22 07:28
• Resolved: 12/Jul/22 07:28

Description

Found unnecessary map copy when doing expression evaluation, it will slow down the codegen when the query include many "case when" or avg/stddev(the reduced expressions include "case when"). In our case, the query include 314 avg, it takes 3+ seconds to generate the projector expressions(Intel(R) Xeon(R) CPU E5-2682 v4 @ 2.50GHz 32cores).