Assuming we skip news, since this is an internal change only.

The main reason I didn't do this earlier is because our (non-builtin) extension modules probably shouldn't be relying on internal API. Instead we should try to use only public API (and sometimes "private", AKA public API with a leading underscore).

How bad would it be to replace uses of _Py_IDENTIFIER() with PyUnicode_InternFromString()?

The main reason I didn't do this earlier is because our (non-builtin) extension modules probably shouldn't be relying on internal API.

It's fully possible to build any stdlib extension as a built-in, even sqlite3.

How bad would it be to replace uses of _Py_IDENTIFIER() with PyUnicode_InternFromString()?

Most users will call execute and friend on a cursor object, not on a connection object, so they won't notice neither performance improvements nor regressions. I'm not sure about the adapter case though; I don't know how widely used they actually are.

The main reason I didn't do this earlier is because our (non-builtin) extension modules probably shouldn't be relying on internal API. Instead we should try to use only public API (and sometimes "private", AKA public API with a leading underscore).

OTOH, I'm totally fine with mainly using public APIs in the sqlite3 module. I'll rewrite it to use public APIs instead.

BTW, thanks for working on this!

BTW, thanks for working on this!

Likewise :)

PTAL. This should result in a small speedup compared to main.

The sqlite3.Connection.cursor() calls are now made directly. Ideally we should do the same with the Cursor.execute* calls, but sqlite3 is inconveniently implemented across multiple files¹, so we can't just call the cursor impl methods directly. I changed the scope of _pysqlite_query_execute, so we can at least speed up the Connection.execute() and Connection.executemany() calls. The remaining methods now use interned strings, with the module always keeping a strong ref to __adapt__, __conform__, and upper to speed up adapters/converters, and finalize to speed up user-defined functions. I did the same for executemany; it is probably not used in hot code, but following the same pattern simplified the code a bit.

Thanks for your review and thoughts, @corona10 & @ericsnowcurrently