… clause: mysql> SELECT SQL_NO_CACHE SQL_CALC_FOUND_ROWS * FROM count_test WHERE b = 555 ORDER BY c LIMIT 5; Results with SQL_CALC_FOUND_ROWS are… sec). Let’s take a look at EXPLAINs: mysql> explain SELECT SQL_CALC_FOUND_ROWS * FROM count_test WHERE b = 999 ORDER BY c LIMIT… seconds for SQL_CALC_FOUND_ROWS. 7+7 seconds in case when two queries used. Filesort: 1.8 seconds for SQL_CALC_FOUND_ROWS. 1.8…
Post: SHOW INNODB STATUS walk through
July 17, 2006 By 40 Comments
…Semaphores information: ———- SEMAPHORES ———- OS WAIT ARRAY INFO: reservation count 13569, signal count 11421 –Thread 1152170336 has waited at ./../include/…mysql tables in use 1, locked 0 MySQL thread id 8079, query id 728899 localhost root Sending data select sql_calc_found_rows *…
Comment: To SQL_CALC_FOUND_ROWS or not to SQL_CALC_FOUND_ROWS?
August 29, 2007 By 57 Comments
…_CACHE count(*) FROM count_test WHERE b = 666;”, count is performed on index without access physical data. But in “EXPLAIN SELECT SQL_CALC_FOUND_ROWS * FROM count_test WHERE b = 999 ORDER BY c LIMIT 5;”, mysql uses index to determine number of rows to examine…
Comment: To SQL_CALC_FOUND_ROWS or not to SQL_CALC_FOUND_ROWS?
September 11, 2009 By 57 Comments
… use count this not will give you true result. in this case you have to use mysql_num_rows or SQL_CALC_FOUND_ROWS , mysql_num_rows runs very slow. we have only one option it is SQL_CALC_FOUND_ROWS. if any…
Post: Is it query which needs to be optimized ?
March 6, 2007 By 9 Comments
… lot of a lot of questions at MySQL Performance Forum as well as from our … techniques. COUNT Many people think counting is fast, some have heard MyISAM is instant with COUNT(*) without …rows in result set, with results set of 100.000+ it becomes pretty inefficient. There is surely SQL_CALC_FOUND_ROWS…
Comment: To SQL_CALC_FOUND_ROWS or not to SQL_CALC_FOUND_ROWS?
November 27, 2008 By 57 Comments
…sql = “SELECT FOUND_ROWS()”; $rows_count = $this->fetchOne($sql); ?> åŽè®°ï¼šè¿™ç§æ–¹æ³•…§ï¼šhttp://www.mysqlperformanceblog.com/2007/08/28/to-sql_calc_found_rows-or-not-to-sql_calc_found_rows/ Mysql [...]
Comment: To SQL_CALC_FOUND_ROWS or not to SQL_CALC_FOUND_ROWS?
August 29, 2007 By 57 Comments
… of mysql server did you use? Does this apply to all current versions or is the SQL_CALC_FOUND_ROWS option more optimized in mysql 5 ? Depending on the availability of indexes, mysql should be able to optimize a SQL_CALC_FOUND_ROWS query in such a way that users do not need to think about using a separate count(*) query anymore…
Post: Are you designing IO bound or CPU bound application ?
December 20, 2006 By 10 Comments
… look boring and obvious but it is extremely important for MySQL Performance Optimization. In fact I probably have to touch it… bound hits the most is there a lot of rows are analyzed – count queries, group by, order by without indexes, search queries… solution is to do select count(*) from messages where user_id=134 or use SQL_CALC_FOUND_ROWS flag for your main select query…
