[MDEV-26284] Selection having joined subselect having a left join produces wrong result in some cases Created: 2021-07-30  Updated: 2022-12-05  Resolved: 2022-12-05

Status: Closed
Project: MariaDB Server
Component/s: Data Manipulation - Subquery
Affects Version/s: 10.6.3
Fix Version/s: N/A

Type: Bug Priority: Major
Reporter: Jan Kohnert Assignee: Unassigned
Resolution: Cannot Reproduce Votes: 0
Labels: None

Attachments: File mariab_bug_minimal_example.sql    

 Description   

Hello,

we stumbled over a wrong result when using a joined subquery having a left join. The query should have returned an empty result set but instead returns some (wrong) lines. The result depends on how we define the where clause in the subselect. Though just rephrasing identical logic in different ways, the results differ, and only one where-condition returns the correct result (note: the result does not even depend on thate particular where condition). Removing the left join from the subquery resolves the problem, too.

I prepared a minimal example showing the bug in the attached file. We use the docker container version 10.6 of mariadb, currently it's version 10.6.3



 Comments   
Comment by Alice Sherepa [ 2022-12-05 ]

Currently, on 10.3 180b2bcd5389082e200f65eb-10.10 there are correct results. Sorry, that the bug was not noticed in time.

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