[jira] [Work logged] (HIVE-23716) Support Anti Join in Hive

["ASF GitHub Bot (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-23716?focusedWorklogId=460414&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-460414 ]

ASF GitHub Bot logged work on HIVE-23716:
-----------------------------------------

                Author: ASF GitHub Bot
            Created on: 17/Jul/20 17:51
            Start Date: 17/Jul/20 17:51
    Worklog Time Spent: 10m 
      Work Description: vineetgarg02 commented on a change in pull request #1147:
URL: https://github.com/apache/hive/pull/1147#discussion_r456588241



##########
File path: common/src/java/org/apache/hadoop/hive/conf/HiveConf.java
##########
@@ -2162,7 +2162,8 @@ private static void populateLlapDaemonVarsSet(Set<String> llapDaemonVarsSetLocal
         "Whether Hive enables the optimization about converting common join into mapjoin based on the input file size. \n" +
         "If this parameter is on, and the sum of size for n-1 of the tables/partitions for a n-way join is smaller than the\n" +
         "specified size, the join is directly converted to a mapjoin (there is no conditional task)."),
-
+    HIVE_CONVERT_ANTI_JOIN("hive.auto.convert.anti.join", false,

Review comment:
       @maheshk114 Have you run all the tests with this feature set to true by default? This change touches existing logic/code and we should definitely run all the existing tests with this set to TRUE.




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Issue Time Tracking
-------------------

    Worklog Id:     (was: 460414)
    Time Spent: 20m  (was: 10m)

> Support Anti Join in Hive 
> --------------------------
>
>                 Key: HIVE-23716
>                 URL: https://issues.apache.org/jira/browse/HIVE-23716
>             Project: Hive
>          Issue Type: Bug
>            Reporter: mahesh kumar behera
>            Assignee: mahesh kumar behera
>            Priority: Major
>              Labels: pull-request-available
>         Attachments: HIVE-23716.01.patch
>
>          Time Spent: 20m
>  Remaining Estimate: 0h
>
> Currently hive does not support Anti join. The query for anti join is converted to left outer join and null filter on right side join key is added to get the desired result. This is causing
>  # Extra computation — The left outer join projects the redundant columns from right side. Along with that, filtering is done to remove the redundant rows. This is can be avoided in case of anti join as anti join will project only the required columns and rows from the left side table.
>  # Extra shuffle — In case of anti join the duplicate records moved to join node can be avoided from the child node. This can reduce significant amount of data movement if the number of distinct rows( join keys) is significant.
>  # Extra Memory Usage - In case of map based anti join , hash set is sufficient as just the key is required to check  if the records matches the join condition. In case of left join, we need the key and the non key columns also and thus a hash table will be required.
> For a query like
> {code:java}
>  select wr_order_number FROM web_returns LEFT JOIN web_sales  ON wr_order_number = ws_order_number WHERE ws_order_number IS NULL;{code}
> The number of distinct ws_order_number in web_sales table in a typical 10TB TPCDS set up is just 10% of total records. So when we convert this query to anti join, instead of 7 billion rows, only 600 million rows are moved to join node.
> In the current patch, just one conversion is done. The pattern of project->filter->left-join is converted to project->anti-join. This will take care of sub queries with “not exists” clause. The queries with “not exists” are converted first to filter + left-join and then its converted to anti join. The queries with “not in” are not handled in the current patch.
> From execution side, both merge join and map join with vectorized execution  is supported for anti join.



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