Boaz Ben-Zvi created DRILL-6881:
-----------------------------------
Summary: Hash-Table insert and probe: Compare hash values before
keys
Key: DRILL-6881
URL: https://issues.apache.org/jira/browse/DRILL-6881
Project: Apache Drill
Issue Type: Improvement
Components: Execution - Relational Operators
Affects Versions: 1.14.0
Reporter: Boaz Ben-Zvi
Assignee: Boaz Ben-Zvi
Fix For: 1.16.0
When checking for existence of a key in the hash table (during _put_ or
_probe_ operations), the value of that key is compared (using generated code)
with a potential match key (same bucket).
This comparison is slightly expensive (e.g., long keys, multi column keys,
checking null conditions, NaN, etc). Instead, if the hash-values of the two
keys are compared first (at practically zero cost), then the costly comparison
can be avoided in case the hash values don't match.
This code change is trivial, and given that the relevant Hash-Table code is
*hot code*, then even minute improvements could add up.
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
