[ https://issues.apache.org/jira/browse/DRILL-4147?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Sean Hsuan-Yi Chu reassigned DRILL-4147: ---------------------------------------- Assignee: Sean Hsuan-Yi Chu > Union All operator runs in a single fragment > -------------------------------------------- > > Key: DRILL-4147 > URL: https://issues.apache.org/jira/browse/DRILL-4147 > Project: Apache Drill > Issue Type: Bug > Reporter: amit hadke > Assignee: Sean Hsuan-Yi Chu > > A User noticed that running select from a single directory is much faster > than union all on two directories. > (https://drill.apache.org/blog/2014/12/09/running-sql-queries-on-amazon-s3/#comment-2349732267) > > It seems like UNION ALL operator doesn't parallelize sub scans (its using > SINGLETON for distribution type). Everything is ran in single fragment. > We may have to use SubsetTransformer in UnionAllPrule. -- This message was sent by Atlassian JIRA (v6.3.4#6332)