Hello Serge,

Serge E. Yakubovich wrote:
>>Description:

First of all I want to thank you for your excelent bug report and apologize for
delayed responce.

>        The same test script I've submitted today to [EMAIL PROTECTED],
> which demonstrates improper(?) behaviour of UPDATE statement on
> 4.0.12 server under FreeBSD, on 4.0.15 server under Alt Linux causes
> segmentation fault.

It is quite difficult to judje what is proper/improper behaviour of such UPDATE
statement.

>From User Variables section in manual:

Note: in a SELECT statement, each expression is evaluated only when it's sent to
the client
...


The general rule is to never assign and use the same variable in the same statement.

<end of quote>

Furthermore Relational Model requires that no operation depends on internal
order of rows in table or order in which rows are processed.
(Tables are Sets - they have no order, Operations on Sets happen "at once")


However no statement should crash mysqld so I am entering your bug report into
Bugs Database with comment that this is improper usage of User Variables.

I was able to narrow down the problem to simple test case and entered it as
#1945 in our Bugs Database
http://bugs.mysql.com/1945

Feel free to follow up discussion there.

> --- SAMPLE 1 (BAD): inproper row is updated

This is questionable.

My feeling is that this should be discussed as separate issue once crashing bug
is fixed.

Comments are welcome.

Best regards

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