Hi, MySQL creates temporary table to complete the query. However, it doesn't tell you whether that temporary table will be in memory or on disk. MySQL's tmp_table_size variable will control the temporary table size.The default tmp_table_size size is 32 MB Temporary tables can either be in the Disk or in Memory. If the space required to build the temporary table is less than or equal to tmp_table_size, MySQL keeps it in memory rather than incur the overhead and time required to write the data to disk and read it again. However, if the space required exceeds tmp_table_size, MySQL creates a disk-based table in its tmpdir directory (often /tmp on Unix systems.) .
mysql> SHOW STATUS LIKE 'Created_tmp_%'; To find out how often that happens, compare the relative sizes of the Created_tmp_tables and Created_tmp_disk_tables counters. Thanks, ViSolve DB Team. ----- Original Message ----- From: <[EMAIL PROTECTED]> To: "MySql Mail List" <mysql@lists.mysql.com> Sent: Thursday, September 07, 2006 8:00 PM Subject: View hidden temporary files Hi. In http://dev.mysql.com/doc/refman/4.1/en/temporary-files.html says "MySQL creates all temporary files as hidden files. This ensures that the temporary files are removed if mysqld is terminated. The disadvantage of using hidden files is that you do not see a big temporary file that fills up the filesystem in which the temporary file directory is located." Is there any form of see the length of the temporary files created by MySQL? Iago.
