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https://issues.apache.org/jira/browse/HIVE-10996?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14592884#comment-14592884
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Laljo John Pullokkaran commented on HIVE-10996:
-----------------------------------------------

Also Why does following pipeline produce wrong result?
GB - (col0, col1, col2)
FIL - (col1, col2)

Child(FIL) should ignore "col0".

Is the result wrong because child is reading the wrong col?
If thats the case then it implies the input schema of child (FIL) and GB output 
col names didn't match.

> Aggregation / Projection over Multi-Join Inner Query producing incorrect 
> results
> --------------------------------------------------------------------------------
>
>                 Key: HIVE-10996
>                 URL: https://issues.apache.org/jira/browse/HIVE-10996
>             Project: Hive
>          Issue Type: Bug
>          Components: Hive
>    Affects Versions: 1.0.0, 1.2.0, 1.1.0, 1.3.0, 2.0.0
>            Reporter: Gautam Kowshik
>            Assignee: Jesus Camacho Rodriguez
>            Priority: Critical
>         Attachments: HIVE-10996.01.patch, HIVE-10996.02.patch, 
> HIVE-10996.03.patch, HIVE-10996.patch, explain_q1.txt, explain_q2.txt
>
>
> We see the following problem on 1.1.0 and 1.2.0 but not 0.13 which seems like 
> a regression.
> The following query (Q1) produces no results:
> {code}
> select s
> from (
>   select last.*, action.st2, action.n
>   from (
>     select purchase.s, purchase.timestamp, max (mevt.timestamp) as 
> last_stage_timestamp
>     from (select * from purchase_history) purchase
>     join (select * from cart_history) mevt
>     on purchase.s = mevt.s
>     where purchase.timestamp > mevt.timestamp
>     group by purchase.s, purchase.timestamp
>   ) last
>   join (select * from events) action
>   on last.s = action.s and last.last_stage_timestamp = action.timestamp
> ) list;
> {code}
> While this one (Q2) does produce results :
> {code}
> select *
> from (
>   select last.*, action.st2, action.n
>   from (
>     select purchase.s, purchase.timestamp, max (mevt.timestamp) as 
> last_stage_timestamp
>     from (select * from purchase_history) purchase
>     join (select * from cart_history) mevt
>     on purchase.s = mevt.s
>     where purchase.timestamp > mevt.timestamp
>     group by purchase.s, purchase.timestamp
>   ) last
>   join (select * from events) action
>   on last.s = action.s and last.last_stage_timestamp = action.timestamp
> ) list;
> 1     21      20      Bob     1234
> 1     31      30      Bob     1234
> 3     51      50      Jeff    1234
> {code}
> The setup to test this is:
> {code}
> create table purchase_history (s string, product string, price double, 
> timestamp int);
> insert into purchase_history values ('1', 'Belt', 20.00, 21);
> insert into purchase_history values ('1', 'Socks', 3.50, 31);
> insert into purchase_history values ('3', 'Belt', 20.00, 51);
> insert into purchase_history values ('4', 'Shirt', 15.50, 59);
> create table cart_history (s string, cart_id int, timestamp int);
> insert into cart_history values ('1', 1, 10);
> insert into cart_history values ('1', 2, 20);
> insert into cart_history values ('1', 3, 30);
> insert into cart_history values ('1', 4, 40);
> insert into cart_history values ('3', 5, 50);
> insert into cart_history values ('4', 6, 60);
> create table events (s string, st2 string, n int, timestamp int);
> insert into events values ('1', 'Bob', 1234, 20);
> insert into events values ('1', 'Bob', 1234, 30);
> insert into events values ('1', 'Bob', 1234, 25);
> insert into events values ('2', 'Sam', 1234, 30);
> insert into events values ('3', 'Jeff', 1234, 50);
> insert into events values ('4', 'Ted', 1234, 60);
> {code}
> I realize select * and select s are not all that interesting in this context 
> but what lead us to this issue was select count(distinct s) was not returning 
> results. The above queries are the simplified queries that produce the issue. 
> I will note that if I convert the inner join to a table and select from that 
> the issue does not appear.
> Update: Found that turning off  hive.optimize.remove.identity.project fixes 
> this issue. This optimization was introduced in 
> https://issues.apache.org/jira/browse/HIVE-8435



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