Got your idea. Thank you very much. Now I know how table cache works :-)
For the bug, yes, it's related to the value of FD_SETSIZE, which is limited to 1024 at my RedHat box. Maybe I should update it to a suitable value. 2010/2/2 Johan De Meersman <vegiv...@tuxera.be>: > > On Mon, Feb 1, 2010 at 4:51 PM, Cui Shijun <rancp...@gmail.com> wrote: >> >> I'm also confused by the difference & relationship between "open >> table" and "open file descriptor" by the table cache. > > "open table" is a MySQL concept. "Open file descriptor" is an OS concept. A > single table (MyISAM) consists of three files: the .frm (description), the > .MYD (data) and the .MYI (indices). Thus, a single open table can correspond > to multiple open files. Additionally, temp tables, sortfiles and whatnot > also consume file descriptors. > >> >> As far as I understand, when a thread ask the global cache for a table: >> * if the table is opened before and currently not used by other >> thread, the request thread will get this table > > "and *there is a cache entry that* is currently not used*" - multiple > entries can exist for the same table. > >> >> * if no table in table cache is available( currently used by other >> thread, or not opened before ), the request thread will open this >> table > > The thread will get a new cache object that opens that table, yes. > >> >> Once open a table, mysql *might?( I'm not sure )* open a file >> descriptor corresponding to the data file of the table. In that case, >> when the number of table opened simultaneously goes too big, mysql >> will use too much file descriptors and then hit the bug 48929. >> >> Your experience( "I've had one occurrence where it grew to 26.000 >> open tables" ) seems to show there must be something wrong with my >> understanding, Hmm... :-( > > I just skimmed over it, but the bug seem related specifically to InnoDB, and > to a highly specific file descriptor number being equal to some form of > hardcoded limit - maybe different OSes or linux distro's have different > values for said limit, or maybe it only occurs under specific conditions. > > > > -- > Bier met grenadyn > Is als mosterd by den wyn > Sy die't drinkt, is eene kwezel > Hy die't drinkt, is ras een ezel > -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql?unsub=arch...@jab.org
