Configure DB API interface attribute `threadsafety = 1`: Threads may share the module, but not connections

[amotl]

About

Relating to the section about thread safety in PEP 0249 ...

• The driver currently configures threadsafety = 2, which means "Threads may share the module and connections."
• Now, it will configure threadsafety = 1, which means "Threads may share the module, but not connections."

Discussion

@hlcianfagna asked:

When using the python driver, is it ok to share a connection with multiple threads each opening their own cursor or should each thread have its own connection?

@amotl said:

Thread-per-connection sounds reasonable.

@mfussenegger said:

I think it currently relies on Python GIL, and afaik if you'd share a connection with the multiprocessing module across processes, things would break. So, it could be worth changing that to 1.

@hlcianfagna said:

I would say the same, should we document it?

References

• Python Driver: Using multiple cursors parallel

/cc @hlcianfagna, @hammerhead, @surister, @proddata, @simonprickett

[amotl]

@hlcianfagna said:

I would say the same, should we document it?

Let me know if you think we should also add a dedicated section within the documentation. I think it could be worth it, if we don't refer to relevant thread safety details anywhere yet. I didn't check yet, though.