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https://issues.apache.org/jira/browse/HIVE-10996?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14592859#comment-14592859
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Jesus Camacho Rodriguez commented on HIVE-10996:
------------------------------------------------
I should have explained it better.
Assume you have the following operators in a plan: {{... - GB - FIL - SEL -
...}}
where, before ColumnPruner is applied, the schemas of the operators are:
{noformat}
GB - (col0, col1, col2)
FIL - (col0, col1, col2)
SEL - (col1, col2)
{noformat}
ColumnPruner is applied topdown through the tree. As SEL only needs col1 and
col2, the required columns for FIL are indeed col1 and col2.
The problem is that ColumnPruner updates FIL schema without taking into account
the operator that is below. Below the FIL operator, we have a GB operator,
which should (and will) still produce tuples consisting of columns {{(col0,
col1, col2)}}. Thus, now there is a mismatch between the tuples in the FIL
operator, which contain 3 columns, and the FIL operator schema, that consists
of {{(col1, col2)}}. The patch fixes this issue by introducing a SEL operator
between the GB and FIL operators, so the plan becomes: {{... - GB - SEL - FIL -
SEL - ...}}
> 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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