Isn't that up to the RDBMS whether than's multithreaded or not? Unless the RDBMS is implemented in Python, CPython doesn't force extension code to be single-threaded. Just Python bytecode.
That's pretty much the point, isn't it? If I need true multithreading, then I am forced to write an extension in C or offload the multithreading work to another process (such as RDBMS in your case). It would have been nice if true multithreading was possible in Python itself. It would immediately make Python more useful in a variety of scenarios where splitting the work into multiple processes is not optimal or more convoluted.
Sure, I guess I'm just used to writing my performance bottlenecks in a lower level language already, so I'm used to the GIL not actually being held most of the time in any intensive computation.
So if I want to call two Fourier transform functions at the same time in Python I can, because neither of them is implemented in Python and so they don't hold the GIL.
That's the kind of parallelism use case I most often see come up, so although the GIL dismayed me early on I've come to see it as pretty irrelevant.
But maybe it makes more sense for other applications, for the performance critical parts of the code to be actual pure Python. I do mostly numerical simulations, so pure Python is usually a non-starter, you fix that long before you think about parallelism.
It's not that I write the whole program in another language, it's that I either write the bottleneck in another language (usually Cython), or it turns out that the Python package I'm calling already has its bottlenecks written in another language, whether I wrote it or not.
Day to day, I'm writing Python code which is actually parallel because a large fraction of the run time is dominated by the by things that aren't pure Python. I suspect this is true even for people who are not going out of their way to make it true. It's simply the case that most RDBM systems, Fourier transforms, etc with Python bindings are not written in Python.
The GIL sounds scary, but I think people overestimate the fraction of time it is actually held in their code.
