MySQL Bugs: #86022: TABLE_SCHEMA column transformed to lower case for upper case database names

Bug #86022	TABLE_SCHEMA column transformed to lower case for upper case database names
Submitted:	20 Apr 2017 16:31	Modified:	21 Apr 2017 7:35
Reporter:	Lukas Eder	Email Updates:
Status:	Can't repeat	Impact on me:	None
Category:	MySQL Server: Data Dictionary	Severity:	S3 (Non-critical)
Version:	5.7.11	OS:	Microsoft Windows (10)
Assigned to:		CPU Architecture:	Any
Tags:	Database name, information_schema, lower case, upper case

Description:
When a database name is written in upper case, it is reported in lower case from the INFORMATION_SCHEMA.COLUMNS.TABLE_SCHEMA column in some situations

How to repeat:
CREATE DATABASE `UPPER`;
CREATE TABLE `UPPER`.`T` (`I` int);

-- These two queries incorrectly report the database name as `upper`
SELECT DISTINCT table_schema FROM information_schema.columns 
WHERE information_schema.columns.table_schema = 'UPPER';

SELECT DISTINCT table_schema FROM information_schema.columns 
WHERE information_schema.columns.table_schema IN ('UPPER');

-- These two queries correctly report the database name as `UPPER`:
SELECT DISTINCT table_schema FROM information_schema.columns 
WHERE concat(information_schema.columns.table_schema) IN ('UPPER');

SELECT DISTINCT table_schema FROM information_schema.columns 
WHERE information_schema.columns.table_schema IN ('UPPER', 'dummy');

Thank you for the bug report. I couldn't repeat with most recent source server on Manjaro Linux:

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Server version: 5.7.19 Source distribution 2017-apr-19

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mysql 5.7 > CREATE DATABASE `UPPER`;
Query OK, 1 row affected (0,00 sec)

mysql 5.7 > CREATE TABLE `UPPER`.`T` (`I` int);
Query OK, 0 rows affected (0,33 sec)

mysql 5.7 > 
mysql 5.7 > -- These two queries incorrectly report the database name as `upper`
mysql 5.7 > SELECT DISTINCT table_schema FROM information_schema.columns 
    -> WHERE information_schema.columns.table_schema = 'UPPER';
+--------------+
| table_schema |
+--------------+
| UPPER        |
+--------------+
1 row in set (0,00 sec)

mysql 5.7 > 
mysql 5.7 > SELECT DISTINCT table_schema FROM information_schema.columns 
    -> WHERE information_schema.columns.table_schema IN ('UPPER');
+--------------+
| table_schema |
+--------------+
| UPPER        |
+--------------+
1 row in set (0,00 sec)

mysql 5.7 > 
mysql 5.7 > -- These two queries correctly report the database name as `UPPER`:
mysql 5.7 > SELECT DISTINCT table_schema FROM information_schema.columns 
    -> WHERE concat(information_schema.columns.table_schema) IN ('UPPER');
+--------------+
| table_schema |
+--------------+
| UPPER        |
+--------------+
1 row in set (0,00 sec)

mysql 5.7 > 
mysql 5.7 > SELECT DISTINCT table_schema FROM information_schema.columns 
    -> WHERE information_schema.columns.table_schema IN ('UPPER', 'dummy');
+--------------+
| table_schema |
+--------------+
| UPPER        |
+--------------+
1 row in set (0,00 sec)

mysql 5.7 > 

mysql 5.7 > SHOW VARIABLES LIKE "%VERSION%";
+-------------------------+---------------------------------+
| Variable_name           | Value                           |
+-------------------------+---------------------------------+
| innodb_version          | 5.7.19                          |
| protocol_version        | 10                              |
| slave_type_conversions  |                                 |
| tls_version             | TLSv1,TLSv1.1                   |
| version                 | 5.7.19                          |
| version_comment         | Source distribution 2017-apr-19 |
| version_compile_machine | x86_64                          |
| version_compile_os      | Linux                           |
+-------------------------+---------------------------------+
8 rows in set (0,00 sec)

mysql 5.7 >

Thanks for looking into this. I omitted the OS because this can be reproduced on Windows and MacOSX as reported here in a jOOQ issue:
https://github.com/jOOQ/jOOQ/issues/5213

Some additional info:

mysql> SHOW VARIABLES LIKE "%VERSION%";

+-------------------------+------------------------------+
| Variable_name           | Value                        |
+-------------------------+------------------------------+
| innodb_version          | 5.7.11                       |
| protocol_version        | 10                           |
| slave_type_conversions  |                              |
| tls_version             | TLSv1,TLSv1.1                |
| version                 | 5.7.11-log                   |
| version_comment         | MySQL Community Server (GPL) |
| version_compile_machine | x86_64                       |
| version_compile_os      | Win64                        |
+-------------------------+------------------------------+

Probably also relevant here:

mysql> SHOW VARIABLES LIKE '%case%';
+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| lower_case_file_system | ON    |
| lower_case_table_names | 2     |
+------------------------+-------+

Let me know if you need any additional info.