MySQL Bugs: #106633: Table names missing from ResultSet metadata with certain queries against 5.7

Bug #106633	Table names missing from ResultSet metadata with certain queries against 5.7
Submitted:	3 Mar 2022 18:18	Modified:	4 Mar 2022 21:59
Reporter:	Jason Young	Email Updates:
Status:	Duplicate	Impact on me:	None
Category:	Connector / J	Severity:	S3 (Non-critical)
Version:	5.7	OS:	Debian (official Docker image)
Assigned to:	MySQL Verification Team	CPU Architecture:	x86 (64-bit)

Description:
I'll start with a brief description; will provide complete code or any other info upon request.

VERY particular queries run with either MysQL Connector/J or MariaDB's driver against MySQL 5.6 result in missing table names from the ResultSet metadata when there should be table names, i.e. `resultSet.getMetadata().getTableName(x)` should return a non-empty String.

I am aware that `SELECT COUNT(*) ...` results in no table names because there is no table names because COUNT(..) does not correspond to a specific column, but `SELECT t0.*, COUNT(*)` should have table names for each column from table `t0`.

I have found some queries where `resultSet.getMetadata().getTableName(x)` returns empty string for every column (for any valid column index `x`) even though only one of the columns should have an empty table name. See below.

Kinda similar to bug 92092.

How to repeat:
Can give a complete Java Gradle or Maven project upon request.

The following SQL:

SELECT
   COUNT(DISTINCT t1.id) AS blah,
   t0.*
 FROM t0
   LEFT JOIN t1 ON t1.t0_id = t0.id
   LEFT JOIN t2 ON t2.id = t1.t2_id
WHERE EXISTS(SELECT 1)
GROUP BY t0.id
ORDER BY blah ASC

run via MySQL Connector/J or MariaDB's driver against a 5.7 MySQL gives a ResultSet where `resultSet.getMetadata().getTableName(x)` is always empty. Any of the following mutations to the above code will make the table names for t0 appear in the result set (e.g. `resultSet.getMetadata().getTableName(2)` returns `t0`):
* Remove the `DISTINCT` or the entire `COUNT(DISTINCT t1.id) AS blah,`
* remove the second `LEFT JOIN`
* remove the GROUP BY clause
* remove the ORDER BY clause
* remove the WHERE clause

This bug is Not Reproducible with MySQL 5.6 or 8.0. It _is_ reproducible with the latest Connector/J and MariaDB drivers.

Tested with official Debian-based MySQL Docker images, OpenJ9 JDK 17, and MySQL driver 8.0.28 on Ubuntu 21.10.

Hi,

I verified the 92092 and I'm not sure what is different here? From what I see this is just a subset of Bug #92092? What am I missing?

thanks

The two may very well have a common root cause. The case I submitted in not reproducible against MySQL 8 whereas 92092 is (or was when it was logged). I also provided different SQL and other info. If you consider this one a duplicate, that is fine by me.

Hi,

I see that sql is different but it looks like identical bug to me. I'll set this up as a duplicate.

Thanks for the report