… /* INT meta=0 nullable=1 is_null=0 */ ### @3=’bar’ /* STRING(9) meta=65033 nullable=1 is_null=0 */ ### SET ### @1… /* INT meta=0 nullable=1 is_null=0 */ ### @3=’hop’ /* STRING(9) meta=65033 nullable=1 is_null=0 */ # at 829… query to a table that has a DDL operation waiting, will block. Why? Because MySQL sees that the old entries in the…
Post: Modeling MySQL Capacity by Measuring Resource Consumptions
March 8, 2011 By 1 Comment
… can take a look at procfs for MySQL process: root@ubuntu:/var/log/mysql# cat /proc/19018/stat 19018 (mysqld…; it is requiring in average 0.54 read operation per second which takes 4ms which adds up …wai 0 0 0 0 0 0 0 0 # String: # Databases # Hosts localhost # InnoDB trxID 3BBF3B55 (1/0%), 3BBF3B5A…
Post: Identifying the load with the help of pt-query-digest and Percona Server
December 29, 2011 By 3 Comments
…as well as InnoDB statistics (such as IO read operations, the number of unique pages the query accessed…atomically, not just for new connections as in MySQL. This is very helpful for measurement as …0 # Boolean: # Full scan 100% yes, 0% no # String: # Databases wp_blog_one (264/84%), wp_blog_tw…
Post: Efficient Boolean value storage for Innodb Tables
April 23, 2008 By 6 Comments
… which can store one of two values – NULL or Empty String. Lets see how these 3 different table format look in… ” would not work) or you can use Null-Aware comparison operator: mysql> select count(*) from cbool where c1NULL; +———-+ | count(*) | +———-+ | 1048576 | +———-+ 1 row…
Post: Updated msl (microslow) patch, installation walk-through!
April 20, 2008 By 17 Comments
… manual. For the following operations you will need to become root user, unless you are already (garfield:~/work/mysql-5.0.51a… just assign an empty string “” to this option. Note: you should put double quotes around the entire string of comma-separated flags…,innodbâ€. Note: You should put double quotes around the entire string of comma-separated flags. Currently “microtime†is mandatory meaning…
Post: GROUP_CONCAT useful GROUP BY extension
September 4, 2006 By 49 Comments
MySQL has useful extention to the GROUP BY operation: function GROUP_CONCAT: GROUP_CONCAT(expr) – This function returns a string result with the… remove loop from PHP to MySQL server side. Also it can be handy to use result concatenated string as part of IN…
Post: Looking at Redis
August 27, 2009 By 27 Comments
… as sets which allow to store sets of strings with support of various set operations. I kind of miss support for something… random single row updates which are hard to batch. With MySQL/Innodb I got server being able to handle some 30… using about 5 cores so you could probably get 4 MySQL instances on this server and get up to 100K updates…
Post: Innodb row size limitation
April 7, 2011 By 12 Comments
…=InnoDB; Now you insert some test data into it: mysql> INSERT INTO example -> VALUES ( ->Â Â NULL, ->Â Â… This means if you insert a 500 character string with all multi-byte characters into a VARCHAR(…impact, as it prevents you from using SQL operators/functions directly on the individual fields you …
Comment: GROUP_CONCAT useful GROUP BY extension
September 7, 2006 By 49 Comments
[...] GROUP_CONCAT useful GROUP BY extension: MySQL has useful extension to the GROUP BY operation: function GROUP_CONCAT: GROUP_CONCAT(expr) – This function returns a string result with the concatenated non-NULL values from a group. [...]
