… “MySQL Query Patterns, Optimized” for Percona MySQL Webinars. If…primary key solution for random selection only work when the…of id’s between 47000 and 50000 with no movies, but your random number…of columns in the index. Example: WHERE (last_name, first_name) = (‘Karwin’, ‘Bill’); Q: On the Dynamic…
Post: How number of columns affects performance ?
September 28, 2009 By 12 Comments
…dynamic rows, however it is not very significant if number of columns is small. For large number of columns dynamic…
Post: Database access Optimization in Web Applications.
September 12, 2006 By 10 Comments
…efficient way. Investigate how dynamic is this information …SELECT COUNT(*) FROM links WHERE domain = ‘mysql.com’; will return only one row while may require to scan hundreds of thousands of…number of columns) – this is not a good practice. However if you can reduce number of queries without a lot of…
Post: Flexviews - part 3 - improving query performance using materialized views
April 4, 2011 By 20 Comments
…) Using the dictionary The following SQL is dynamically generated by the flexviews.get_sql() function… this column. It is used to prevent wide innodb primary keys on the MV. mysql> select …the number of lines in the order_lines table, three orders of magnitude more quickly than COUNT(*). mysql> select…
Post: ORDER BY ... LIMIT Performance Optimization
September 1, 2006 By 100 Comments
… if we stick to simple MySQL using multiple indexes on most selective columns would be good idea for performance of such queries. For example… rethink your indexing. Also note – number of records scanned to provide result set will be very dynamic based on particular constant and other…
Post: How much overhead is caused by on disk temporary tables
August 16, 2007 By 26 Comments
…column. mysql> explain select count(*) cnt,c from gt group by c order by null limit 10; +—-+————-+——-+——+—————+——+———+——+———+—————–+ | id | select… at this number I … For 4M of rows mysql> select count… MySQL will implement support of dynamic…
Comment: To SQL_CALC_FOUND_ROWS or not to SQL_CALC_FOUND_ROWS?
August 29, 2007 By 57 Comments
…SELECT SQL_CALC_FOUND_ROWS * FROM count_test WHERE b = 999 ORDER BY c LIMIT 5;”, mysql uses index to determine number of…picking physical data which takes some time (because columns are not included in index). I think … I use a stored procedure that accept a dynamic sql query, an offset and a limit …
