Re: Thread safeness

[Sasha Pachev]

Marcelo Criscuolo wrote:
> Hello folks,
> 
> 	I'm looking for some information about MySQL thread-safeness, but
> I'm not understanding well the manual
> (http://dev.mysql.com/doc/mysql/en/Threaded_clients.html). It says "If you
> don't need interrupts or timeouts, you can just compile a thread-safe
> client library (mysqlclient_r) and use this", but later it says
> mysql_real_connect() is not thread safe.
> 
> 	Could someone, please, help me understanding this?
> 
> 	1. How exactly is the thread-safeness level of mysqlclient_r
> 	library?
> 
> 	2. Can I share a connection between threads or not?
> 
> 	3. Just using mysqlclient_r instead of mysqlclient is enough to
> 	get thread safeness?

Marcelo:

The "thread-safety" of mysqlclient_r as opposed to the regular one is simply in 
blocking disruptive signals during network I/O operations. If you want to share 
the same connection between thread, you will need a mutex around some calls (see 
the docs you mentioned above). If you are using mysql_use_result(), you will 
need to have a mutex from the call to mysql_query() to mysql_free_result() for 
sure. If you do mysql_store_result(), you can release it after 
mysql_store_result() returns.

-- 
Sasha Pachev
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