Set MySQL Connection Count On The Fly

Occasionally you'll run into a situation in which the connection count you've configured for MySQL is too low. This often happens on load balanced applications. You can use the following commands to view and set the connection limit on the fly:

mysql> select @@global.max_connections;
+--------------------------+
| @@global.max_connections |
+--------------------------+
|                     1000 |
+--------------------------+
1 row in set (0.00 sec)

mysql> set @@global.max_connections = 3000;
Query OK, 0 rows affected (0.00 sec)

original url : https://boxpanel.blueboxgrp.com/public/the_vault/index.php/Set_MySQL_Connection_Count_On_The_Fly

how to execute mutli-statements In Ruby/Mysql

there is a tip when you need to execute multi-statements in Ruby/Mysql.
the wrong version:

require 'mysql'
dbh=Mysql.real_connect('localhost','root','pass','db')
dbh.set_server_option( Mysql::OPTION_MULTI_STATEMENTS_ON )
stmt="select * from contents limit 1;\n" *10
puts stmt
dbh.query( stmt )
puts dbh.stat # got the CR_COMMANDS_OUT_OF_SYNC error.


....

the correct version:


require 'mysql'
dbh=Mysql.real_connect('localhost','root','pass','db')
dbh.set_server_option( Mysql::OPTION_MULTI_STATEMENTS_ON )
stmt="select * from contents limit 1;\n" *10
puts stmt
dbh.query( stmt ) { |res|
puts "number of rows is #{res.num_rows()}"
}
puts dbh.stat

what 's the differents?
Wow,
dbh.query( stmt ) { |res|

puts "number of rows is #{res.num_rows()}"
}

and

dbh.query( stmt )

when multi-statements was executed , a group of result set were present ,
even we need not the the data in the result set .
so we should iterate the result sets and clear it before the next mysql-related statement .

References :
1,http://www.tmtm.org/en/mysql/ruby/ , offical site of Ruby/Mysql
2,http://dev.mysql.com/doc/refman/5.0/en/c-api-multiple-queries.html , one query multiple statment using C API on Mysql.
3,http://www.kitebird.com/articles/ruby-mysql.html , a goog tutorial for ruby/Mysql