… to MySQL 5.6. Next interesting thing are the last two columns of the table above and the values for ‘Handler_read_key’, ‘Handler_read_next‘ and ‘Handler_read_rnd_next‘. MariaDB 5.5 with Hash Joins enabled is doing less Handler reads as compared to when…
Post: Multi Range Read (MRR) in MySQL 5.6 and MariaDB 5.5
March 21, 2012 By 10 Comments
…bound workload, mentioned above. Counter Name MySQL 5.5 MySQL 5.6 MySQL 5.6 w/ read_rnd_bufer_size=4M MariaDB 5.5 … Handler_read_key 508833 623738 622184 508913 507516 Handler_read_next 574320 574320 572889 574320 572889 Handler_read_rnd_next 136077 136094 136366 136163 136435 Innodb_buffer_pool_read…
Post: Index Condition Pushdown in MySQL 5.6 and MariaDB 5.5 and its performance impact
March 12, 2012 By 12 Comments
… in preparation for the talk comparing the optimizer enhancements in MySQL 5.6 and MariaDB 5.5. We are taking a… optimizer enhancement Index Condition Pushdown (ICP). Its available in both MySQL 5.6 and MariaDB 5.5 Now let’s take…
Post: What does Handler_read_rnd mean?
June 15, 2010 By 15 Comments
MySQL‘s SHOW STATUS command has two counters that are often confusing and result in “what does that mean?” questions: Handler_read_rnd Handler_read_rnd_next As… read a row based on a primary key value. Handler_read_rnd_next is incremented when handler::rnd_next() is called. This is basically a cursor operation: read the “next…
Post: Ultimate MySQL variable and status reference list
January 8, 2011 By 4 Comments
…MySQL manual, …Handler_prepareblogpercona.commanual Handler_read_firstblogpercona.commanual Handler_read_keyblogpercona.commanual Handler_read_lastblogpercona.commanual Handler_read_nextblogpercona.commanual Handler_read_prevblogpercona.commanual Handler_read_rndblogpercona.commanual Handler_read_rnd…
Post: MySQL: Followup on UNION for query optimization, Query profiling
August 14, 2006 By 12 Comments
…Handler_delete | 0 | | Handler_discover | 0 | | Handler_prepare | 0 | | Handler_read_first | 0 | | Handler_read_key | 1 | | Handler_read_next | 42250 | | Handler_read_prev | 0 | | Handler_read_rnd | 0 | | Handler_read_rnd_next | 0 | | Handler_rollback | 0 | | Handler_savepoint | 0 | | Handler…
Post: How to estimate query completion time in MySQL
April 22, 2008 By 14 Comments
… to choose another thread and watch only its status, but MySQL doesn’t currently let you do that.) The solution was… -r -i 10 | grep Handler_read_rnd_next — ignore the first line of output… | Handler_read_rnd_next | 429224 | So the server was reading roughly 43K rows per second…
Comment: What does Handler_read_rnd mean?
June 25, 2010 By 15 Comments
… (0.00 sec) mysql> show status like ‘Handler_read_rnd_next‘ ; +———————–+——-+ | Variable_name | Value | +———————–+——-+ | Handler_read_rnd_next | 4 | +———————–+——-+ 1 row in set (0.00 sec) Handler_read_rnd_next was not incremented…
Post: Joining on range? Wrong!
May 17, 2010 By 10 Comments
… of MySQL, however unless…Handler_read%’; +———————–+——–+ | Variable_name | Value | +———————–+——–+ | Handler_read_first | 0 | | Handler_read_key | 3 | | Handler_read_next | 118181 | | Handler_read_prev | 0 | | Handler_read_rnd | 0 | | Handler_read_rnd_next…
Comment: What does Handler_read_rnd mean?
June 26, 2010 By 15 Comments
… the copy the second time does not increment Handler_read_rnd_next. However, scanning the original mysql.user does. So it is not the size… mystery that I do not understand, though, is how incrementing Handler_read_rnd_next is avoided on a MyISAM table without the query cache…(READ_RECORD *info) { int tmp; while ((tmp=info->file->rnd_next(info->record))) { /* rnd_next can return RECORD_DELETED for MyISAM when one thread is reading…
