Re: PL/Python initialization cleanup

> On Dec 31, 2025, at 16:47, Peter Eisentraut <peter@eisentraut.org> wrote:
> 
> As I was working through steps to make PL/Python more thread-safe, I noticed that the initialization code of PL/Python is pretty messy.  I think some of this has grown while both Python 2 and 3 were supported, because they required different initialization steps, and we had some defenses against accidentally running both at the same time.  But that is over, and right now a lot of this doesn't make sense anymore.  For example, the function PLy_init_interp() said "Initialize the Python interpreter ..." but it didn't actually do this, and PLy_init_plpy() said "initialize plpy module" but it didn't do that either (or at least they used the term "initialize" in non-standard ways).
> 
> Here are some patches to clean this up.  After this change, all the global initialization is called directly from _PG_init(), and the plpy module initialization is all called from its registered initialization function PyInit_plpy().  (For the thread-safety job, the plpy module initialization will need to be rewritten using a different API.  That's why I'm keen to have it clearly separated.)  I also tried to add more comments and make existing comments more precise.  There was also some apparently obsolete or redundant code that could be deleted.
> 
> Surely, all of this will need some more rounds of careful scrutiny, but I think the overall code arrangement is correct and an improvement.
> <v1-0001-plpython-Remove-commented-out-code.patch><v1-0002-plpython-Clean-up-PyModule_AddObject-uses.patch><v1-0003-plpython-Remove-duplicate-PyModule_Create.patch><v1-0004-plpython-Streamline-initialization.patch>

I just did an eyeball review. Overall looks good to me. The cleanup, as explained in the patch email, makes sense to me. Only a nit comment on 0002:

1 - 0002
```
+	if (PyModule_AddObject(mod, modname, exc) < 0)
+	{
+		Py_XDECREF(exc);
+		PLy_elog(ERROR, "could not add exceptions %s", name);
+	}
```

Plural “exceptions” is a little confusing. What about “could not add exception object”?

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/