[ https://issues.apache.org/jira/browse/HIVE-15114?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Sergio Peña updated HIVE-15114: ------------------------------- Attachment: HIVE-15114.3.patch > Remove extra MoveTask operators > ------------------------------- > > Key: HIVE-15114 > URL: https://issues.apache.org/jira/browse/HIVE-15114 > Project: Hive > Issue Type: Sub-task > Components: Hive > Affects Versions: 2.1.0 > Reporter: Sahil Takiar > Assignee: Sergio Peña > Attachments: HIVE-15114.3.patch, HIVE-15114.WIP.1.patch, > HIVE-15114.WIP.2.patch > > > When running simple insert queries (e.g. {{INSERT INTO TABLE ... VALUES > ...}}) there an extraneous {{MoveTask}s is created. > This is problematic when the scratch directory is on S3 since renames require > copying the entire dataset. > For simple queries (like the one above), there are two MoveTasks. The first > one moves the output data from one file in the scratch directory to another > file in the scratch directory. The second MoveTask moves the data from the > scratch directory to its final table location. > The first MoveTask should not be necessary. The goal of this JIRA it to > remove it. This should help improve performance when running on S3. > It seems that the first Move might be caused by a dependency resolution > problem in the optimizer, where a dependent task doesn't get properly removed > when the task it depends on is filtered by a condition resolver. > A dummy {{MoveTask}} is added in the > {{GenMapRedUtils.createMRWorkForMergingFiles}} method. This method creates a > conditional task which launches a job to merge tasks at the end of the file. > At the end of the conditional job there is a MoveTask. > Even though Hive decides that the conditional merge job is no needed, it > seems the MoveTask is still added to the plan. > Seems this extra {{MoveTask}} may have been added intentionally. Not sure why > yet. The {{ConditionalResolverMergeFiles}} says that one of three tasks will > be returned: move task only, merge task only, merge task followed by a move > task. -- This message was sent by Atlassian JIRA (v6.3.4#6332)