Details
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Bug
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Status: Closed (View Workflow)
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Major
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Resolution: Duplicate
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10.3.8, 10.2(EOL), 10.3(EOL), 10.4(EOL)
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None
Description
Description:
When using the LAG() window function in an arithmetic expression, the result may be wrong
How to repeat:
This statement:
WITH tab(t, company, quote) AS (
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SELECT 1 AS t, 'G' AS company, 40 AS quote
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UNION SELECT 2 , 'G', 60
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UNION SELECT 3 , 'S', 60
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UNION SELECT 4, 'S', 20
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)
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SELECT DISTINCT company, quote - LAG(quote) OVER(PARTITION BY company ORDER BY t)
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FROM tab;
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produces wrong output:
company e
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--------------
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G (null)
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S (null)
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Remove the DISTINCT keyword....
WITH tab(t, company, quote) AS (
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SELECT 1 AS t, 'G' AS company, 40 AS quote
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UNION SELECT 2 , 'G', 60
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UNION SELECT 3 , 'S', 60
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UNION SELECT 4, 'S', 20
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)
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SELECT company, quote - LAG(quote) OVER(PARTITION BY company ORDER BY t) e
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FROM tab;
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to get this:
company e
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--------------
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G (null)
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G 20
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S (null)
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S -40
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As can be seen, the DISTINCT keyword should have no effect on this query.
This is also described in this stack overflow question:
https://stackoverflow.com/q/49700278/521799
The same bug appears also in MySQL:
https://bugs.mysql.com/bug.php?id=92503
Attachments
Issue Links
- is duplicated by
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- Closed
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Activity
After fix for MDEV-14791 was pushed we now get the correct results
MariaDB [test]> SELECT 1+LAG(i2) OVER(ORDER BY i1) FROM t1;
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+-----------------------------+
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| 1+LAG(i2) OVER(ORDER BY i1) |
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+-----------------------------+
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| NULL |
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| 41 |
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| 61 |
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| 61 |
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+-----------------------------+
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4 rows in set (0.01 sec)
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|
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MariaDB [test]> SELECT distinct 1+LAG(i2) OVER(ORDER BY i1) FROM t1;
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+-----------------------------+
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| 1+LAG(i2) OVER(ORDER BY i1) |
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+-----------------------------+
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| NULL |
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| 41 |
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| 61 |
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+-----------------------------+
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3 rows in set (0.01 sec)
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|
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MariaDB [test]> SELECT distinct 1+LAG(i2,0) OVER(ORDER BY i1) FROM t1;
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+-------------------------------+
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| 1+LAG(i2,0) OVER(ORDER BY i1) |
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+-------------------------------+
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| 41 |
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| 61 |
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| 21 |
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+-------------------------------+
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3 rows in set (0.00 sec)
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MariaDB [test]> SELECT distinct 1+LEAD(i2) OVER(ORDER BY i1) FROM t1;
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+------------------------------+
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| 1+LEAD(i2) OVER(ORDER BY i1) |
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+------------------------------+
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| 61 |
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| 21 |
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| NULL |
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+------------------------------+
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3 rows in set (0.00 sec)
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|
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MariaDB [test]> SELECT distinct 1+rank() OVER(ORDER BY i1) FROM t1;
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+----------------------------+
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| 1+rank() OVER(ORDER BY i1) |
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+----------------------------+
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| 2 |
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| 3 |
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| 4 |
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| 5 |
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+----------------------------+
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4 rows in set (0.00 sec)
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So closing this as a duplicate of MDEV-14791
Thanks for the report! Reproducible on MariaDB 10.2,10.3
create table t1 (i1 int, i2 int);insert into t1 values (1,40), (2,60), (3,60),(4,20);MariaDB [test]> SELECT 1+LAG(i2) OVER(ORDER BY i1) FROM t1;+-----------------------------+| 1+LAG(i2) OVER(ORDER BY i1) |+-----------------------------+| NULL || 41 || 61 || 61 |+-----------------------------+4 rows in set (0.001 sec)MariaDB [test]> SELECT distinct 1+LAG(i2) OVER(ORDER BY i1) FROM t1;+-----------------------------+| 1+LAG(i2) OVER(ORDER BY i1) |+-----------------------------+| NULL |+-----------------------------+1 row in set (0.000 sec)MariaDB [test]> SELECT distinct 1+LAG(i2,0) OVER(ORDER BY i1) FROM t1;+-------------------------------+| 1+LAG(i2,0) OVER(ORDER BY i1) |+-------------------------------+| 41 |+-------------------------------+1 row in set (0.000 sec)MariaDB [test]> SELECT distinct 1+LEAD(i2) OVER(ORDER BY i1) FROM t1;+------------------------------+| 1+LEAD(i2) OVER(ORDER BY i1) |+------------------------------+| 61 |+------------------------------+1 row in set (0.002 sec)MariaDB [test]> SELECT distinct 1+rank() OVER(ORDER BY i1) FROM t1;+----------------------------+| 1+rank() OVER(ORDER BY i1) |+----------------------------+| 2 |+----------------------------+1 row in set (0.001 sec)As a temporary workaround, it is possible to use derived table or CTE table
MariaDB [test]> select distinct * from (SELECT 1+LAG(i2) OVER(ORDER BY i1) FROM t1) tmp;+-----------------------------+| 1+LAG(i2) OVER(ORDER BY i1) |+-----------------------------+| NULL || 41 || 61 |+-----------------------------+3 rows in set (0.003 sec)