… number of connections for each status: mysql> pager awk -F ‘|’ ‘{print $6}’ | sort | uniq -c | sort -r PAGER set to ‘awk -F ‘|’ ‘{print $6}’ | sort… querying INFORMATION_SCHEMA. For instance, counting the number of sleeping connections can be done with: mysql> SELECT COUNT(*) FROM INFORMATION_SCHEMA.PROCESSLIST…
Post: Review of MySQL 5.6 Defaults Changes
October 8, 2012 By 10 Comments
…great summary of defaults changes in MySQL 5.6 compared to MySQL 5.5 In general there are…at 2000 Same thing. What number of max connections has to do with number of hosts which can potentially…need to be configured. sort_buffer_size = 256K Good choice for very small sorts but more complicated queries…
Post: Implications of Metadata Locking Changes in MySQL 5.5
February 1, 2013 By 9 Comments
… large number of MySQL 5.0 and 5.1 installations that would upgrade or are in the process of upgrading to MySQL 5… end_log_pos 773 Table_map: `test`.`test` mapped to number 17 #130201 11:21:35 server id 1 end_log….000002 | | statistics | 0.000005 | | preparing | 0.000006 | | executing | 0.000001 | | Sorting result | 0.000002 | | Sending data | 0.000040 | | end | 0.000003…
Post: MySQL Limitations Part 4: One thread per connection
October 27, 2010 By 14 Comments
…about the way MySQL handles connections, allocating one thread per connection to the server. MySQL is a … pools and persistent connections combined with a large number of application servers can lead to a …, NotABug. I’m thinking of the lack of sort-merge joins or intra-query parallelism, for example…
Post: Percona Live MySQL Conference and Expo 2013 – News from the Committee – Tutorial Selection Complete
December 3, 2012 By 1 Comment
…was not the case at a MySQL conference. There are several MySQL HA related tutorials: Using Tungsten …The committee is furiously working on rating the huge number of session proposals. I just finished a …, there are hundreds of session proposals to sort through. Everyone on the committee has his …
Post: MySQL Upgrade Webinar Questions Followup
June 28, 2012 By 7 Comments
… upgrade of MySQL 5.0 to MySQL 5.5 should be rather safe from data standpoint. There are still possibilities for sorting order and data type related changes, so you still need to run mysql_upgrade to check if… making database binary incompatible with MySQL. Our focus on compatibility is indeed so high there are number of great features which are…
Post: Should we give a MySQL Query Cache a second chance ?
April 10, 2011 By 64 Comments
… is appealing to improve performance for MySQL Applications ? Make it Lockless Can we re-implement MySQL Query Cache so it is lockless… case can be done through some sort of garbage collection. Support for Delayed Invalidation Many MySQL application do not need absolutely up… rather large set of applications. Many applications in MySQL have very large number of queries doing updates through primary key and use…
Post: Multi Range Read (MRR) in MySQL 5.6 and MariaDB 5.5
March 21, 2012 By 10 Comments
… in between where secondary key tuples are buffered and then sorted by the primary key values, and then instead of point… rows than MySQL 5.5, as can be seen by the numbers reported for the status counter Innodb_rows_read. While MySQL 5.6 is also reporting increased numbers for the…
Post: MySQL EXPLAIN limits and errors.
July 24, 2006 By 6 Comments
… number of passes MySQL had to perform and so number of row combinations really examined. LIMIT is not taken into account while estimating number… restricts how many rows will be examined MySQL will still print full number. Here is example: mysql> explain select * from lt limit 10… from other tables. No information about using disk for sort or temporary tables MySQL always calls it “filesort” even if it is…
Post: MySQL Users Conference - Innodb
May 9, 2007 By 6 Comments
… static record format ? (static record format for sort used by MyISAM may cause sort files to be much larger than table itself… cases. Now In MySQL 5.1+ it is also possible to fix this problem for cases when number of rows in auto… Google released so many MySQL patches so we can call patched version GoogleSQL. Among them there are number of patches to make…
