On Tue, 2003-10-28 at 00:15, Guilhem Bichot wrote: > On Mon, 2003-10-27 at 22:01, Dathan Vance Pattishall wrote:
> So the conclusion is: unfortunately, the symlink support in MySQL was > not designed for "synonyming", as far as DDL (Data Definition Language - > CREATE TABLE / DROP TABLE / ALTER TABLE) commands are concerned. It was > designed with the thought that symlinks are to be used to point to a > *different* directory (another partition where there is more room, or > another device to balance disk load). For DDL commands MySQL always > expects a table to exist only once, i.e. to have only one name. Putting, > in the database directory, a symlink and the real table means giving 2 > names to one table... > > I will add a note about this into our manual soon. I understand this is > is an inconvenience for you; you will be safe if you always do the DDL > commands (ALTER TABLE, in your case) on the real table. It's ok to do > DML commands (INSERT/DELETE/UPDATE/LOADDATA, which fortunately occur > much more often than ALTER TABLE normally) on both tables indifferently. Sorry, I should have been more accurate in the last sentence. It's ok to do DML commands *always* on the real table OR *always* on the synonym table. If thread1 uses the real table's name, and thread 2 uses the synonym, the query cache can be fooled: - set global query_cache_size=1000000; - connection1: select * from tbl_; - connection2: insert into tbl values(1); - connection1: select * from tbl_; you don't see the inserted row! - connection1: flush tables (empties caches); select * from tbl_; you see the inserted row! Even if you disable the query cache, I am not sure if it's safe to use both names; there could be some other fooled caches in MySQL. Simply put, things go wild when the real name and the synonym are both used. Which impacts the interest of using synonyms (hum). And FLUSH TABLES is a remedy. I'll add this to the manual. Regards, Guilhem -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
