From: Michael Widenius
Date: December 22 2009 7:38am
Subject: re: system_charset_info
List-Archive: http://lists.mysql.com/internals/37607
Message-Id: <19248.30574.961446.670491@narttu.askmonty.org>
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Hi!

>>>>> "Yan" == Yan Yu <yan2yu2@stripped> writes:

Yan> Dear Mysql experts,
Yan>      I just started working on MySql source code at Facebook.
Yan> I hope you could help shed some light on one question I have:

Yan> I am working on MySQL 5.138:
Yan>     I am changing system_charset_info in sql/mysqld.cc from
Yan> system_charset_info= &my_charset_utf8_general_ci;
Yan> to:
Yan> system_charset_info= &my_charset_latin1;

Yan> and this change seems having broken many tests in mysql-test-run.
Yan> As part of this investigation, we have found one bug in mysql source  
Yan> code and
Yan> one test case in which the test writer did not consider the case where
Yan> system_charset_info could be something other than  
Yan> my_charset_utf8_general_ci, e.g., my_charset_latin1, where a char is  
Yan> represented by a single byte.
Yan> There are still many other broken test cases that we need to  
Yan> investigate.

What is the bug ?

Yan> My Q is:
Yan> have anyone tried to change system_charset_info in sql/mysqld.cc and  
Yan> what is your experience? what changes you need to make in order to  
Yan> make all the included test suites pass?

I don't think this has been considered;  At least it's clear that while
writing test for the test suite, this was never considered.

Yan> Any pointers on what this change may break is also very appreciated!
Yan> Best,

I would expect that most, if not all things should work even if you
change the character set.

Most errors in this case should mainly be in the test suite.

If you run mysql-test-run --force and examine the results, ignoring
errors in the test suite, you should be able to get some assurance
that your change works.

Regards,
Monty
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