…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 12 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 6 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: Debugging problems with row based replication
May 6, 2010 By 10 Comments
…affected (0.02 sec) Insert a single “seed” row into the table: INSERT INTO repl.t1 VALUES (); Query OK, 1 row affected…in the WHERE clause…many rows were modified during a transaction. You should always set read_only = true on your MySQL slaves to prevent accidental changes in…
Post: Should you move from MyISAM to Innodb ?
January 12, 2009 By 53 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 …
