[ 
https://issues.apache.org/jira/browse/HIVE-23716?focusedWorklogId=461616&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-461616
 ]

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

                Author: ASF GitHub Bot
            Created on: 21/Jul/20 14:42
            Start Date: 21/Jul/20 14:42
    Worklog Time Spent: 10m 
      Work Description: pgaref commented on a change in pull request #1147:
URL: https://github.com/apache/hive/pull/1147#discussion_r458151829



##########
File path: 
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/mapjoin/VectorMapJoinAntiJoinGenerateResultOperator.java
##########
@@ -0,0 +1,218 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.hive.ql.exec.vector.mapjoin;
+
+import org.apache.hadoop.hive.ql.CompilationOpContext;
+import org.apache.hadoop.hive.ql.exec.JoinUtil;
+import org.apache.hadoop.hive.ql.exec.vector.VectorizationContext;
+import org.apache.hadoop.hive.ql.exec.vector.VectorizedRowBatch;
+import org.apache.hadoop.hive.ql.exec.vector.expressions.VectorExpression;
+import 
org.apache.hadoop.hive.ql.exec.vector.mapjoin.hashtable.VectorMapJoinHashSet;
+import 
org.apache.hadoop.hive.ql.exec.vector.mapjoin.hashtable.VectorMapJoinHashSetResult;
+import 
org.apache.hadoop.hive.ql.exec.vector.mapjoin.hashtable.VectorMapJoinHashTableResult;
+import org.apache.hadoop.hive.ql.metadata.HiveException;
+import org.apache.hadoop.hive.ql.plan.OperatorDesc;
+import org.apache.hadoop.hive.ql.plan.VectorDesc;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+
+// TODO : This class is duplicate of semi join. Need to do a refactoring to 
merge it with semi join.
+/**
+ * This class has methods for generating vectorized join results for Anti 
joins.
+ * The big difference between inner joins and anti joins is existence testing.
+ * Inner joins use a hash map to lookup the 1 or more small table values.
+ * Anti joins are a specialized join for outputting big table rows whose key 
exists

Review comment:
       nit: whose key DOES NOT exist




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

    Worklog Id:     (was: 461616)
    Time Spent: 2.5h  (was: 2h 20m)

> 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: 2.5h
>  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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