Gary, ----- Alkuperäinen viesti ----- Lähettäjä: "Gary Richardson" <[EMAIL PROTECTED]> Vastaanottaja: "Heikki Tuuri" <[EMAIL PROTECTED]> Kopio: <[EMAIL PROTECTED]> Lähetetty: Thursday, October 21, 2004 4:49 AM Aihe: Re: Char to Varchar on Innodb
> I'm not too worried about it myself, but I can see how less magic on a > database server is better. > > Without actually trying it, if I mix CHAR's and VARCHAR's in a table, > does SHOW CREATE TABLE reflect the internal conversion? > > If you wanted to reduce fragmentation in an Innodb table, wouldn't all > the CHAR fields need to be left-packed? For example, you'd still get if the field to be UPDATEd is fixed size, then an UPDATE does not cause fragmentation. That is what I meant. > fragmentation if your columns went CHAR, VARCHAR, CHAR. I guess that > is unless the engine underneath did this automagically. > > Thanks. Best regards, Heikki Innobase Oy InnoDB - transactions, row level locking, and foreign keys for MySQL InnoDB Hot Backup - a hot backup tool for InnoDB which also backs up MyISAM tables http://www.innodb.com/order.php Order MySQL support from http://www.mysql.com/support/index.html > On Wed, 20 Oct 2004 11:29:30 +0300, Heikki Tuuri > <[EMAIL PROTECTED]> wrote: > > Gary, > > > > those 'silent column specification changes' affect all table types. That > > feature has caused lots of user questions over years. It is in the TODO to > > remove that feature from MySQL, because it is not standards compliant. In > > InnoDB, a reason to use a CHAR column in some cases is to reduce > > fragmentation if there are lots of updates to that column. A CHAR column > > takes a fixed space. Silent column specification changes in many cases > > defeat this optimization which would otherwise be available to users. > > > > Best regards, > > > > Heikki Tuuri > > Innobase Oy > > Foreign keys, transactions, and row level locking for MySQL > > InnoDB Hot Backup - a hot backup tool for InnoDB which also backs up MyISAM > > tables > > http://www.innodb.com/order.php > > > > Order MySQL technical support from https://order.mysql.com/ > > > > .................... > > > > > > Hey, > > > > From http://dev.mysql.com/doc/mysql/en/Silent_column_changes.html: > > > > <snip> > > If any column in a table has a variable length, the entire row becomes > > variable-length as a result. Therefore, if a table contains any > > variable-length columns (VARCHAR, TEXT, or BLOB), all CHAR columns > > longer than three characters are changed to VARCHAR columns. This > > doesn't affect how you use the columns in any way; in MySQL, VARCHAR > > is just a different way to store characters. MySQL performs this > > conversion because it saves space and makes table operations faster. > > See section 15 MySQL Storage Engines and Table Types. > > </snip> > > > > Does this affect all table types? I'm curious if this is happening on > > my InnoDB tables as well. No problems, just curiosity.. > > > > Thanks. > > > > > > -- > > MySQL General Mailing List > > For list archives: http://lists.mysql.com/mysql > > To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED] > > > > -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
