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Kevin Wilfong commented on HIVE-3915: ------------------------------------- https://reviews.facebook.net/D8019 > Union with map-only query on one side and two MR job query on the other > produces wrong results > ---------------------------------------------------------------------------------------------- > > Key: HIVE-3915 > URL: https://issues.apache.org/jira/browse/HIVE-3915 > Project: Hive > Issue Type: Bug > Components: Query Processor > Affects Versions: 0.11.0 > Reporter: Kevin Wilfong > Assignee: Kevin Wilfong > > When a query contains a union with a map only subquery on one side and a > subquery involving two sequential map reduce jobs on the other, it can > produce wrong results. It appears that if the map only queries table scan > operator is processed first the task involving a union is made a root task. > Then when the other subquery is processed, the second map reduce job gains > the task involving the union as a child and it is made a root task. This > means that both the first and second map reduce jobs are root tasks, so the > dependency between the two is ignored. If they are run in parallel (i.e. the > cluster has more than one node) no results will be produced for the side of > the union with the two map reduce jobs and only the results of the other side > of the union will be returned. > The order TableScan operators are processed is crucial to reproducing this > bug, and it is determined by the order values are retrieved from a map, and > hence hard to predict, so it doesn't always reproduce. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira