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Pritesh Maker commented on DRILL-6845: -------------------------------------- [~ben-zvi] adding the link to the PR - https://github.com/apache/drill/pull/1606 > Eliminate duplicates for Semi Hash Join > --------------------------------------- > > Key: DRILL-6845 > URL: https://issues.apache.org/jira/browse/DRILL-6845 > Project: Apache Drill > Issue Type: Improvement > Components: Execution - Relational Operators > Affects Versions: 1.14.0 > Reporter: Boaz Ben-Zvi > Assignee: Boaz Ben-Zvi > Priority: Minor > Fix For: 1.16.0 > > > 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)