…56 sec) Records: 0 Duplicates: 0 Warnings: 1 mysql> SHOW WARNINGS\G *************************** 1. row *************************** Level: Note Code: 1831 Message: …Key definitions: # KEY `col2` (`col2`), # KEY `col2_2` (`col2`,`col3`) # Column types: # `col2` int(11) default null # `col3` varchar(200…
Post: MySQL Query Patterns, Optimized - Webinar questions followup
June 3, 2013 By 2 Comments
… tradeoff of this solution is that it requires storing another column, and reinitializing the sequence after making certain insert/update/delete… matter, and it would have to match the order of columns in the index. Example: WHERE (last_name, first_name) = (‘Karwin… were trying to determine the last episode of each TV show. Couldn’t you have used a SUBQUERY to fetch and…
Post: Replication in MySQL 5.6: GTIDs benefits and limitations - Part 2
May 30, 2013 By 6 Comments
… the replication topology when using GTID-based replication. That will show where GTIDs shine and where improvements are expected. This is… to know the coordinates of the last event executed: s1> show slave status\G [...] Executed_Gtid_Set: 219be3a9-c3ae-11e2-b985-0800272864ba… 3d3871d1-c3ae-11e2-b986-0800272864ba:4 ? A ‘Last_Executed_GTID’ column would have been useful. In our case we can check…
Comment: Solving INFORMATION_SCHEMA slowness
May 6, 2013 By 25 Comments
… a function to discover the structure of a table, its columns and primary key, etc. Using I_S was too slow… used the simple “DESCRIBE ” statement (which is a synonym for “SHOW COLUMNS FROM “). That has less information than all of I_S…
Post: How to recover table structure from InnoDB dictionary
April 22, 2013 By 4 Comments
… ON Frm file corrupt, zeroed out, lost or SHOW CREATE TABLE crashes MySQL There is yet another… | 4 | +———-+——+———————+———-+——+——-+———+ SYS_COLUMNS Table SYS_COLUMNS stores fields names and type information of the table. CREATE TABLE `SYS_COLUMNS` ( `TABLE_…
Comment: Benchmarking Percona Server TokuDB vs InnoDB
May 8, 2013 By 32 Comments
… compression: i.e. you have a separate table with TEXT column, which stores data, like this comment. In this case it… 5.6 more to see what kind of performance it shows with compression.
Post: The write cache: Swap insanity tome III
April 19, 2013 By 5 Comments
… 30539 21120 2 3 81 13 0 Note the free column going down and the cache one going up and then…”. A quick survey of the servers I have access to showed that the common values are 20 and 40. I simply…
Post: Percona XtraDB Cluster 5.5.30-23.7.4 for MySQL now available
April 17, 2013 By 2 Comments
… library will be available for download from our repositories. Benchmark showing the impact of memory allocators on MySQL performance can be…). Parallel applying would fail in case mixed CHAR and VARCHAR columns would be used in foreign key definitions. Bug fixed #1100496…
Post: Query_cache and column level privileges
August 6, 2007 By 5 Comments
… and under user ‘vadim’ Before query execution: mysql> show global status like ‘qcache%’; +————————-+———-+ | Variable_name | Value | +————————-+———-+ | …assumption – the query that includes tables with defined column level privileges can’t be cached – but …
Post: How number of columns affects performance ?
September 28, 2009 By 12 Comments
… less space), table with 1 tinyint column and char(99) column and table with 100 tinyint columns. The former two tables have the same row length but have number of column different… shows there is surely the problem with dynamic row format table with many columns. But is it because of large number of columns…
