[Lazarus] Multithreaded app with PostgreSQL connection
Michael Van Canneyt
michael at freepascal.org
Mon Jun 20 19:38:50 CEST 2016
On Mon, 20 Jun 2016, Ondrej Pokorny wrote:
> I have a multithreaded application where every thread needs to connect
> to the same PostgreSQL database. How to design the DB connectivity for a
> multithreaded application correctly?
Best is to have every thread use it's own connection.
If you want only a single connection, then you should make sure all Database
and Transaction properties (plus setting them to Nil) are protected by a
critical section: there are non-threadsafe lists involved.
> I see that TPQConnection has an FConnectionPool. So is it thread-safe?
Not if you don't follow the above steps.
> Create a TPQConnection in the main thread; create
> TSQLQuery+TSQLTransaction in a (different) thread and connect it to to
> the TPQConnection from main thread via the Database property?
> Or do I need a TPQConnection per thread?
> I somehow failed to find any information about sqldb and multithreading:
Because it is not thread safe. It is on my todo list.
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