…the order of columns in the index. Example: WHERE (last_name, first_name) = (‘Karwin’, ‘Bill’); Q: On the Dynamic Pivot, the…the MySQL community at our events. The next one is in London on November 11-12, 2013. We also look forward to the Percona Live MySQL…
Post: How to recover table structure from InnoDB dictionary
April 22, 2013 By 4 Comments
…is a table identifier. We will need the table id to find indexes of the table. mysql> select * from SYS_TABLES WHERE…last_update | 6 | 1799 | 4 | 0 | +———-+—–+————-+——-+———+——+——+ So, we know all fields of the table, we can get the type. Is it enough for the…
Post: Edge-case behavior of INSERT...ODKU
October 27, 2012 By 6 Comments
…the PRIMARY KEY is always going to be considered as being defined first. So, MySQL checks our INSERT, sees that the next auto-inc value is…THE LAST ROW, the one where the id is equal to the auto-increment max value, which is the one that got updated. The secondary UNIQUE on username is…
Post: Identifying the load with the help of pt-query-digest and Percona Server
December 29, 2011 By 3 Comments
…SELECT option_name, option_value FROM wp_options WHERE autoload = ‘yes’\G This is the actual part of the output dealing with analysis of the query that is…the underlying tables involved and the query execution plan used by MySQL. The end result might be that you end up limiting the…
Post: Implications of Metadata Locking Changes in MySQL 5.5
February 1, 2013 By 9 Comments
…is blocked for any kind of operation. Let’s see the profiling information for one of the queries that was blocked to see where the…Value | +—————+——-+ | Open_tables | 30 | | Opened_tables | 0 | +—————+——-+ 2 rows in set (0.00 sec) session10 > select…
Post: When is MIN(DATE) != MIN(DATE) ?
September 4, 2012 By 5 Comments
…SELECT MIN(t.update_time) FROM (SELECT uid, MIN(update_time) AS “update_time” FROM foo WHERE update_time IS…values might work, there is no guarantee.’ It turned out that an application had submitted the odd datetime, and because the value passed the…
Post: Percona XtraDB Cluster: Failure Scenarios with only 2 nodes
July 25, 2012 By 6 Comments
…the connection between the nodes is gone: percona1 mysql> insert into percona values (0,’percona1′,’jaime’); Query OK, 1 row affected (0.02 sec) percona1 mysql> select…
Post: How to obtain the "LES" (Last Executed Statement) from an Optimized Core Dump?
September 9, 2012 By 9 Comments
…/sql_select.cc:312 #21 mysql_execute_…value_list, 3135 lex->duplicates, 3136 lex->ignore))) 3137 { 3138 res= handle_select…where the query string is hiding (query_string > string > str), we can use: (gdb) p thd->query_string.string.str In the future. Conclusion: the Last…
Post: MySQL 5.6.10 Optimizer Limitations: Index Condition Pushdown
March 14, 2013 By 2 Comments
…the following query in particular that had this surprising outcome: mysql> SELECT * FROM cast_info WHERE…is actually very different from the “rows” value seen above. This is because the second part of the condition -note like ‘%Jaime%’- is…
Post: Percona Replication Manager, a solution for MySQL high availability with replication using Pacemaker
November 29, 2011 By 102 Comments
…the last year, the frustration of many of us at Percona regarding issues with MMM has grown to a level where…The credentials to test MySQL. Default is to run select count(*) on mysql.user table, so the user given should at least have select…
