Bug #78480 heap engine wastes CPU re-calculating hash values
Submitted: 18 Sep 2015 15:11 Modified: 2 Oct 2015 15:43
Reporter: Tor Didriksen Email Updates:
Status: Closed Impact on me:
None 
Category:MySQL Server: Storage Engines Severity:S3 (Non-critical)
Version:5.7 OS:Any
Assigned to: CPU Architecture:Any

[18 Sep 2015 15:11] Tor Didriksen 
Description:
my_hash_sort_simple consumes lots of CPU

How to repeat:
run sysbench "disctinct ranges"

Suggested fix:
cache computed hash values
[2 Oct 2015 15:43] Paul DuBois 
Noted in 5.7.9, 5.8.0 changelogs.

Insert overhead for the MEMORY storage table was reduced by caching
computed hash values.