Boaz Ben-Zvi created DRILL-6845: ----------------------------------- Summary: Eliminate duplicates for Semi Hash Join Key: DRILL-6845 URL: https://issues.apache.org/jira/browse/DRILL-6845 Project: Apache Drill Issue Type: Sub-task Components: Execution - Relational Operators Affects Versions: 1.14.0 Reporter: Boaz Ben-Zvi Assignee: Boaz Ben-Zvi Fix For: 1.15.0
Following DRILL-6735: The performance of the new Semi Hash Join may degrade if the build side contains excessive number of join-key duplicate rows; this mainly a result of the need to store all those rows first, before the hash table is built. Proposed solution: For Semi, the Hash Agg would create a Hash-Table initially, and use it to eliminate key-duplicate rows as they arrive. Proposed extra: That Hash-Table has an added cost (e.g. resizing). So perform "runtime stats" – Check initial number of incoming rows (e.g. 32k), and if the number of duplicates is less than some threshold (e.g. %20) – cancel that "early" hash table. -- This message was sent by Atlassian JIRA (v7.6.3#76005)