Re: [gnome-db] Threads.

[Vivien Malerba <vmalerba gmail com>]

2009/7/24 Bas Driessen <bas driessen xobas com>

Hello,

Question regarding libgda and threads.

I open a data source connection (ie: gda_connection_open_from_dsn) in thread 1 and then I try to perform any action on the connection (ie: gda_connection_statement_execute_select) in thread 2. If I do this in Postgresql all works fine. If I try to do this in MySQL then the system appears to hang in thread 2. I assume because thread 1 is holding a lock on the connection.

How can I remove the lock that is set by function gda_connection_open_from_dsn so I can access the connection information from thread 2?

Perhaps slightly out of libgda scope, but is there a difference between Postgresql and MySQL when it comes to threads and locking? It appears that Postgresql does not have that concept or perhaps by default configured not to use threads?

The same kind of limitation also applies to PostgreSQL which is usually not compiled with thread support in client libraries. The discrepancies between databases' client libraries regarding threads have led me to create the GDA_CONNECTION_OPTIONS_THREAD_SAFE flag (in 4.1, not in 4.0) where a connection can be used by any thread, regardless of the thread which created the connection (in fact a thread is created per connection and the user threads synchronize with that thread when running statements, it relies on the GdaThreadWrapper object).

Vivien