Re: UPDATE with WHERE+ORDER+LIMIT error(?) - test shell script (fwd)
Alexander Keremidarski <[email protected]>
| Newsgroups | gmane.comp.db.mysql.general,gmane.comp.db.mysql.bugs |
|---|---|
| Organization | MySQL AB |
| Message-ID | <[email protected]> |
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 -- Are you MySQL certified? -> http://www.mysql.com/certification For technical support contracts, visit https://order.mysql.com/?ref=msal __ ___ ___ ____ __ / |/ /_ __/ __/ __ \/ / Mr. Alexander Keremidarski <[email protected]> / /|_/ / // /\ \/ /_/ / /__ MySQL AB, Full-Time Developer /_/ /_/\_, /___/\___\_\___/ Sofia, Bulgaria <___/ www.mysql.com -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[email protected]