…applies both to implicit and explicit ones) but as …as you can query temporary tables too: mysql> select sum(data…tables (both in memory and not): mysql> select * from information_schema.global…LENGTH: 0 CREATE_TIME: NULL UPDATE_TIME: NULL *************************** 2. row *************************** …
Post: InnoDB's gap locks
March 27, 2012 By 15 Comments
…SELECT FOR UPDATE. InnoDB provides REPEATABLE READ for read-only SELECT, but it behaves as if you use READ COMMITTED for all write queries…second one is a global variable that affects all sessions and …MySQL uses REPEATABLE READ as the default isolation level so it needs to lock the index records and…
Comment: InnoDB's gap locks
April 13, 2012 By 15 Comments
…mysql> select * from t; +——+——–+ | i | c | +——+——–+ | 1 | miguel | | 3 | andy | | 5 | aaron | | 8 | repls | +——+——–+ Then I start two transactions, session1 and…
Post: MySQL Configuration Wizard Updated
January 26, 2012 By 5 Comments
…updated version of the MySQL Configuration Wizard we announced…, rather than improving this one. I have a list …query analysis tool, a way to register a server’s essential characteristics and then get advice when there’s a new release that might be beneficial for you, and so on. I have selected…
Post: Scaling problems still exist in MySQL 5.5 and Percona Server 5.5
May 20, 2011 By 11 Comments
…one query but yet mimics real world values distribution. The query looks something like this: SELECT * FROM table WHERE deleted = 0 AND…
Post: Flexviews - part 3 - improving query performance using materialized views
April 4, 2011 By 12 Comments
… An incrementally refreshable view (that is, one which uses the incremental method) can be updated much more efficiently, by examining a …and customers tables directly (the tables on which dashboard_customer_sales is built), then the query would take significantly longer (40+ minutes): mysql> SELECT…
Post: Fighting MySQL Replication Lag
September 22, 2008 By 6 Comments
… any other query execution. So if you have transaction containing millions of simple updates instead of one large update to help MySQL replication… select rows for modification – spread it out and have separate select and update queries. In such case slave will only need to run UPDATE Example: UPDATE…
Post: Ultimate MySQL variable and status reference list
January 8, 2011 By 4 Comments
…MySQL manual, especially the option and…Select_full_joinblogpercona.commanual Select_full_range_joinblogpercona.commanual Select_rangeblogpercona.commanual Select_range_checkblogpercona.commanual Select…
Post: Identifying the load with the help of pt-query-digest and Percona Server
December 29, 2011 By 3 Comments
…one causing the highest load is the SELECT wp_options query, this is basically a unique way of identifying the query and…queries that you can use to gather more data about the underlying tables involved and the query execution plan used by MySQL…
Post: Should we give a MySQL Query Cache a second chance ?
April 10, 2011 By 63 Comments
… applications. Many applications in MySQL have very large number of queries doing updates through primary key and use primary key for selects. I believe in… fashion. This is one I’m most unsure about though as MySQL Query Cache is most useful for complex expensive queries, for which tracking…
