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Date: Wed, 29 Jun 2016 16:16:37 +0200
From: Till Haug <till@veezoo.com>
To: <dev@drill.apache.org>
Message-ID: <1559c84cdd3.dd66c1d550726.4058759938604893816@veezoo.com>
Subject: Critical Bug with Column Name Clash
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Hi guys


My company encountered a critical bug in Apache Drill 1.7.0 (and earlier ve=
rsions) and we=E2=80=99re not sure if this is an already known problem.
If there are two columns with the same name in two different tables, there =
seems to be a conflict.


Example 1:
select t.emp_no as col_one, d.emp_no as col_two
from mysqlaws.employees.titles as t, mysqlaws.employees.dept_manager as d
where t.emp_no =3D d.emp_no


Result 1:
emp_no emp_no0
110022 null
110022 null
110039 null
=E2=80=A6


Expected Result 1:
emp_no emp_no0
110022 110022
110022 110022
110039 110039
=E2=80=A6


Example 2:
select t.from_date as col_one, d.from_date as col_two
from mysqlaws.employees.titles as t, mysqlaws.employees.dept_manager as d
where t.emp_no =3D d.emp_no


Result 2:
col_one col_two
1985-01-01 null
1985-01-01 null
1991-10-01 null
=E2=80=A6


Expected Result 2:
col_one col_two
1985-01-01    1985-01-01
1991-10-01    1985-01-01
1991-10-01    1991-10-01
=E2=80=A6


In Example 1 there is no rename happening and the col_two is all nulls.
In Example 2 the rename is happening, but the col_two is still all nulls.


When we run these queries directly against the databases (both mssql and my=
sql) they work as expected.


If you=E2=80=99d like to directly reproduce it, feel free to use our server=
 we set up with the following storage plugin


{
 "type": "jdbc",
 "driver": "com.mysql.jdbc.Driver",
 "url": "jdbc:mysql://vz-test.cbnbj0e1vrwg.eu-central-1.rds.amazonaws.com:8=
008",
 "username": "vz_master",
 "password": "vzpassword",
 "enabled": false
}


Thank you and All the Best
Till


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