… the amazing MySQL manual, especially the option and variable …_write_timeoutblogpercona.commanual newblogpercona.commanual no_defaultsblogpercona.commanual Not_flushed_delayed_… unique_checksblogpercona.commanual updatable_views_with_limitblogpercona.commanual Uptimeblogpercona.commanual Uptime_…
Post: When the subselect runs faster
March 18, 2010 By 9 Comments
… sensible strategy if there is no LIMIT, however it is poor chose …MySQL to do retrieve rows in sorted order and checking if it matches our original WHERE clause with…MySQL index choice: mysql> explain select * from table FORCE INDEX(PRIMARY) where (col1=’A'||col1=’B') order by id desc limit 20 offset…
Post: 10+ Ways to Crash or Overload MySQL
November 13, 2007 By 20 Comments
… unavailable server with any MySQL version if you have access to it with normal privileges….offset by keeping myisam_sort_buffer_size low, but then performance would suffer. Prepared Statements Number – Happily now there is a limit…all memory. However there is no per user limit so one user can consume…
Post: A case for MariaDB's Hash Joins
May 31, 2012 By Leave a Comment
…the size of the buffer ‘join_buffer_space_limit‘. This variable controls the maximum allowed size of… table with no WHERE clause The SQL used for this test together with its EXPLAIN output as returned by MySQL… the secondary key. Even though MySQL 5.6 uses MRR to offset the effect of random access of …
Comment: To SQL_CALC_FOUND_ROWS or not to SQL_CALC_FOUND_ROWS?
August 29, 2007 By 57 Comments
…is not true, in “EXPLAIN SELECT SQL_NO_CACHE count(*) FROM count_test WHERE b = 666;”, … count_test WHERE b = 999 ORDER BY c LIMIT 5;”, mysql uses index to determine number of rows to examine…because second query which accepts limit and offset do the same thing but one with SQL_CALC_FOUND_ROWS just …
Post: How InnoDB handles REDO logging
February 3, 2011 By 19 Comments
…no, operation code, data> This translates into operations such as <0, 2600, ‘insert’, ‘after record at offset… will never complete. Both the MySQL configuration and hardware will affect…with XtraDB allows much larger logs beyond the InnoDB limit of 4G. As a side effect of logging there is no…
Post: Is your server's performance about to degrade?
May 18, 2010 By 13 Comments
…here’s the magic — the byte offset of the worst performer in…with microsecond granularity, too. It’s interesting to note that while these Quit; and Statistics; and similar no-tables, no…’s where improvements to the MySQL source code are necessary….server isn’t pushing the limits of performance doesn’t…
Comment: MySQL Server Memory Usage
December 20, 2012 By 21 Comments
…mysql,test #replicate_do_db=crmdb #replicate_do_db=newcrmdb #auto-increment-increment = 3 #auto-increment-offset…limit…mysql-slow-query.log # Default to using old password format for compatibility with mysql…
Post: What exactly is read_rnd_buffer_size
July 24, 2007 By 4 Comments
…performed having only row pointers together with key value – which are offsets for MyISAM and primary key …LIMIT 10 it is unlikely to help as MySQL will stop fetching rows by pointers quickly For me this means since MySQL…buffer and sort file so there would be no need for read_rnd_buffer, if the …
