多线程与 PostgreSQL JDBC

Question

I'm still a student and not so experienced with multithreading and databases so I might have missed some obvious stuff - hoping for an answer at a more beginner level. I'm busy creating a dummy Java application that allows users to submit subway station locations and then lookup the nearest station to their location. This is all happening over HTTP. The backend for this application is PostgreSQL (with PostGis) and I connect to the database via the PostgreSQL JDBC. I want my application to be as multithreaded as possible. Every time I receive a new HTTP connection, I spin up a new thread and service the users request. But I'm not sure how much point there is to this if reads and writes to the database themselves cannot be parallel. According to this , PostgreSQL JDBC is not thread safe. But what does that mean exactly? Does that just mean that reads and writes within a single connection are not thread safe (ie in each instance of DriverManager.getConnection())? But what about if I made a new connection every time an HTTP request came in? Would that be safe to do in parallel? And would that affect performance badly? Any other suggestions on broad approach to take?

Answer 1

JDBC in general is not thread-safe, not just the Postgres driver.

This means you can not run multiple statements created from the same Connection instance in multiple threads at the same time.

If you want to run two statements in parallel, you need to create two different physical connections to the database.

As creating connections isn't cost-free, the usual approach is to have a connection pool (eg through a ConnectionPoolDataSource ) that keeps a set of connections open. The application then takes connections from the pool and puts them back when the query (or transaction) is done.