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ASF GitHub Bot commented on DRILL-4147: --------------------------------------- Github user sudheeshkatkam commented on a diff in the pull request: https://github.com/apache/drill/pull/555#discussion_r73022440 --- Diff: exec/java-exec/src/test/java/org/apache/drill/TestUnionDistinct.java --- @@ -32,6 +34,9 @@ public class TestUnionDistinct extends BaseTestQuery { private static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(TestUnionDistinct.class); + private static final String sliceTargetSmall = "alter session set `planner.slice_target` = 1"; + private static final String sliceTargetDefault = "alter session set `planner.slice_target` = " + ExecConstants.SLICE_TARGET_DEFAULT; --- End diff -- ```private static final String sliceTargetDefault = "RESET `planner.slice_target`"; ``` > 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: Aman Sinha > > 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)