----- Am 1. Apr 2016 um 21:56 schrieb shawn l.green shawn.l.gr...@oracle.com:
> Correct. MyISAM is not a transactional storage engine. It has no concept > of COMMIT or ROLLBACK. Changes to it are controlled by a full table lock > and as soon as the change is complete, the table is unlocked and is > immediately visible to every other session. > > What the replication system has done is to extend the length of that > lock until the transaction completes to avoid situations where changes > appear "out of sequence" to what is recorded in the Binary Log. >> So when transaction is rollbacked, the inserted data in the MyISAM table >> remains >> ? > > Correct. All of the changes that could be undone were undone. MyISAM > changes can't be undone so they stayed in place. > Aah. OK. > Try this as an analogy. > > MyISAM tables are like writing directly with ink on paper. If you can > complete the write, you have changed the row. > > InnoDB tables are like whiteboards. You can undo your pending changes > before someone else (one of the background threads of the InnoDB engine) > makes the changes permanent. > > The Binary Log is like a recipe used to rebuild your data in case it > goes boom. If you start from a backup then repeat the sequence of > actions as they were recorded in the Binary Log since that backup was > created, you should wind up with exactly the same data you had before > the problem. If there is a problem with that sequence (actions are out > of order) then rebuilding that data could be a problem. > > Sequence makes a big difference even in less esoteric settings. Try this... > > Start with your phone lying flat on your desk (screen up) pointing > directly away from you. Roll it 45 degrees to the right. Now lift it > vertically towards you 90 degrees (maintain the roll). The phone is now > pointing straight up but the screen is turned away from you. > > Then try those same actions in reverse order. lift first, then roll it > to the right. In this case the screen is pointing in your general > direction but the whole thing is leaning off to one side. I don't understand the example completely, but i understand what you want to say: Changing the order of statements may lead to a different result. Bernd Helmholtz Zentrum Muenchen Deutsches Forschungszentrum fuer Gesundheit und Umwelt (GmbH) Ingolstaedter Landstr. 1 85764 Neuherberg www.helmholtz-muenchen.de Aufsichtsratsvorsitzende: MinDir'in Baerbel Brumme-Bothe Geschaeftsfuehrer: Prof. Dr. Guenther Wess, Dr. Alfons Enhsen, Renate Schlusen (komm.) Registergericht: Amtsgericht Muenchen HRB 6466 USt-IdNr: DE 129521671 -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql
