[IMPALA-2281] Use a better hash function than FNV for exchanges

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: Impala 2.2
• Fix Version/s: Impala 2.11.0
• Component/s: Backend
• Target Version: Product Backlog
• Assignee: Tianyi Wang
• Reporter: Tim Armstrong
• Created: 02/Sep/15 00:02
• Updated: 09/Nov/17 00:21
• Resolved: 09/Nov/17 00:21

Description

The FNV hash function is used in Impala to hash data for exchanges and there are various utility functions for computing FNV hashes of different data types. There are clearly superior alternatives. For example, Murmur2 is already in the codebase, is faster to compute, and has better distribution properties.

Issue Links

• relates to: IMPALA-5168 Codegen hash computation in DataStreamSender::Send for partition exchange.