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https://issues.apache.org/jira/browse/HIVE-17148?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Vlad Gudikov updated HIVE-17148:
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Status: Patch Available (was: Open)
> Incorrect result for Hive join query with COALESCE in WHERE condition
> ---------------------------------------------------------------------
>
> Key: HIVE-17148
> URL: https://issues.apache.org/jira/browse/HIVE-17148
> Project: Hive
> Issue Type: Bug
> Components: CBO
> Affects Versions: 2.1.1
> Reporter: Vlad Gudikov
> Assignee: Vlad Gudikov
> Attachments: HIVE-17148.1.patch, HIVE-17148.patch
>
>
> The issue exists in Hive-2.1. In Hive-1.2 the query works fine with cbo
> enabled:
> STEPS TO REPRODUCE:
> {code}
> Step 1: Create a table ct1
> create table ct1 (a1 string,b1 string);
> Step 2: Create a table ct2
> create table ct2 (a2 string);
> Step 3 : Insert following data into table ct1
> insert into table ct1 (a1) values ('1');
> Step 4 : Insert following data into table ct2
> insert into table ct2 (a2) values ('1');
> Step 5 : Execute the following query
> select * from ct1 c1, ct2 c2 where COALESCE(a1,b1)=a2;
> {code}
> ACTUAL RESULT:
> {code}
> The query returns nothing;
> {code}
> EXPECTED RESULT:
> {code}
> 1 NULL 1
> {code}
> The issue seems to be because of the incorrect query plan. In the plan we can
> see:
> predicate:(a1 is not null and b1 is not null)
> which does not look correct. As a result, it is filtering out all the rows is
> any column mentioned in the COALESCE has null value.
> Please find the query plan below:
> {code}
> Plan optimized by CBO.
> Vertex dependency in root stage
> Map 1 <- Map 2 (BROADCAST_EDGE)
> Stage-0
> Fetch Operator
> limit:-1
> Stage-1
> Map 1
> File Output Operator [FS_10]
> Map Join Operator [MAPJOIN_15] (rows=1 width=4)
>
> Conds:SEL_2.COALESCE(_col0,_col1)=RS_7._col0(Inner),HybridGraceHashJoin:true,Output:["_col0","_col1","_col2"]
> <-Map 2 [BROADCAST_EDGE]
> BROADCAST [RS_7]
> PartitionCols:_col0
> Select Operator [SEL_5] (rows=1 width=1)
> Output:["_col0"]
> Filter Operator [FIL_14] (rows=1 width=1)
> predicate:a2 is not null
> TableScan [TS_3] (rows=1 width=1)
> default@ct2,c2,Tbl:COMPLETE,Col:NONE,Output:["a2"]
> <-Select Operator [SEL_2] (rows=1 width=4)
> Output:["_col0","_col1"]
> Filter Operator [FIL_13] (rows=1 width=4)
> predicate:(a1 is not null and b1 is not null)
> TableScan [TS_0] (rows=1 width=4)
> default@ct1,c1,Tbl:COMPLETE,Col:NONE,Output:["a1","b1"]
> {code}
> This happens only if join is inner type, otherwise HiveJoinAddNotRule which
> creates this problem is skipped.
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