…is the importance of the size of the buffer used for sorting the secondary key tuples. If the buffer size is…is the combined size of the secondary key tuples fetched, and N is the buffer size. In MySQL 5.6 the buffer size…
Post: Join Optimizations in MySQL 5.6 and MariaDB 5.5
April 4, 2012 By 2 Comments
…is used in conjunction with BKA and that is MRR Key-ordered Scan. Let’s see what this optimization actually is…’ optimizer_switch=’mrr_sort_keys=on’ optimizer_…is not entirely visible in the manual either for MariaDB or MySQL, but you need to appropriately increase read_rnd_buffer_size/mrr_buffer_size…
Post: How is join_buffer_size allocated?
July 5, 2010 By 9 Comments
…MySQL configuration, we quite often want to know how various buffer sizes are used. This matters because some buffers (sort_buffer_size…buffer is allocated. Its meaning is actually “minimum join buffer size.” Here’s the code, in sql/sql_select.cc in…
Post: How fast can you sort data with MySQL ?
August 18, 2007 By 26 Comments
…sort merge passes – may be it is sort merge which is inefficient with large sort_buffer_size ? mysql> set sort_buffer_size=100000000; Query OK, 0 rows affected (0.00 sec) mysql…
Post: Ultimate MySQL variable and status reference list
January 8, 2011 By 4 Comments
…in the Percona documentation or forums. So I present to you what is…sort_buffer_sizeblogpercona.commanual Sort_merge_passesblogpercona.commanual Sort_rangeblogpercona.commanual Sort_rowsblogpercona.commanual Sort_scanblogpercona.commanual sporadic_binlog_dump_failblogpercona.commanual sql_auto_is…
Post: Can we improve MySQL variable handling ?
February 18, 2012 By 8 Comments
…mysql> set global sort_buffer_size=DEFAULT; Query OK, 0 rows affected (0.00 sec) mysql> select @@global.sort_buffer_size; +—————————+ | @@global.sort_buffer_size | +—————————+ | 2097152 | +—————————+ 1 row in…
Post: Using MyISAM in production
June 17, 2006 By 35 Comments
…sort_buffer_size and MySQL could crash or go swapping. Second – table will be locked while repair is going. If this is…cached in key_buffer while data is cached in OS cache. It is performance issue as system call is … wrong result sets or crashes. Here is my list what I think MyISAM tables are good…
Post: What to tune in MySQL Server after installation
September 29, 2006 By 116 Comments
… to work as MySQL DBAs or be involved with MySQL Performance in some way is to ask them what should be tuned in MySQL Server straight after…_buffer_pool_size This is very important variable to tune if you’re using Innodb tables. Innodb tables are much more sensitive to buffer size… workload specific. If you have simple queries there is no reason to increase sort_buffer_size even if you have 64GB of memory to…
Post: What's required to tune MySQL?
July 27, 2011 By 4 Comments
… to deliver huge wins. If MySQL is actually badly configured, you can hurt…MySQL installations don’t suffer from the variety and severity of problems we write about here. Examples include what…In addition to unlikely circumstances, I sometimes see unlikely settings, such as making the sort buffer size…
Post: MySQL Server Memory Usage
May 17, 2006 By 18 Comments
…the question how should they estimate memory consumption by MySQL Server in given configuration. What is the formula they could use. The reasons …measure what you get in practice and how memory consumption reacts to changing various variables. For example you may find out increasing sort_buffer_size…
