…where. You may not use sub-queries or any non-deterministic functions like NOW() or RAND(). HAVING clauses, ORDER BY clauses…number of lines in the order_lines table, three orders of magnitude more quickly than COUNT(*). mysql…performance and query results. The view type does not usually* affect…
Post: Flexviews - part 3 - improving query performance using materialized views
April 4, 2011 By 20 Comments
Post: MySQL EXPLAIN limits and errors.
July 24, 2006 By 6 Comments
…where clause. This however would not tell you full story, especially now as MySQL…many rows will be examined in total. This can be rather wrong. One thing to consider is number of rows analyzed for given table…
Post: How adding another table to JOIN can improve performance ?
August 1, 2008 By 12 Comments
…affect performance. Of course in this example you can use index (B,A) but there are many…number of rows for second table in join is estimated same in original query) and we get the range clause on “info” table…
Post: Using any general purpose computer as a special purpose SIMD computer
May 16, 2011 By 5 Comments
…mysql> load data infile ‘/tmp/words’ into table words (chars); Query OK, 6033 rows affected…where clause. This creates boundary conditions for our query. Any set of integers can be broken up into as many…
Post: Beware of MySQL Data Truncation
February 7, 2009 By 4 Comments
…in the column) it truncates the value, performs index lookup, scanning all rows (just 3 in my trivial example) and when filtering them out because value really does not match the where clause…mysql> set sql_mode=STRICT_ALL_TABLES; Query OK, 0 rows affected (0.00 sec) mysql…
Post: MySQL Backup tools used by Percona Remote DBA for MySQL
March 13, 2013 By 8 Comments
…MySQL service we recognize that reliable backups are one of the most important things we can bring to the table. In…where clause or filters weren’t quite right The application had a bug causing data to be removed or overwritten A table…
Post: Debugging problems with row based replication
May 6, 2010 By 12 Comments
…performed by this statement in…affected (0.02 sec) Rows matched: 1 Changed: 1 Warnings: 0 On the slave, SHOW SLAVE STATUS now reports an error (many…Table_map: `repl`.`t1` mapped to number 15 #100506 12:42:56 server id 1 end_log_pos 340718 Update_rows: table…in the WHERE clause…
Post: Should you move from MyISAM to Innodb ?
January 12, 2009 By 59 Comments
…number of tables, slow data load and ALTER TABLE and others. Another big one is COUNT(*) without where clause…work etc. Note Performance also affects Operations aspects a…performance analyzes) as well as it exercises not so common paths in the MySQL server – in…Really. MyISAM for many applications can …
