The following optimisations can be applied to _pysqlite_connection_begin():

1. Return an int instead of a PyObject pointer

   Per now, we do Py_RETURN_NONE and Py_DECREF(result) if _pysqlite_connection_begin() was successful (normally the case). There's no reason to do this. Let's just it the C way: return -1 on error and 0 if things are ok.


2. Defer error checking till post sqlite3_finalize()

   Any error code returned by sqlite3_step() will also be returned by sqlite3_finalize() for the same statement. From the SQLite docs:
   "If the most recent evaluation of statement S failed, then sqlite3_finalize(S) returns the appropriate error code or extended error code."


3. Move _pysqlite_connection_begin() to Modules/_sqlite/cursor.c

   The single use is in _pysqlite_query_execute() in cursor.c. Moving it makes it possible for the compiler to apply more optimisations. At least so I've heard :)
   (As a side effect, the namespace will be cleaner.)

New changeset 3446516ffa92c98519146253153484291947b273 by Erlend Egeberg Aasland in branch 'main':
bpo-44042: Optimize sqlite3 begin transaction (GH-25908)
https://github.com/python/cpython/commit/3446516ffa92c98519146253153484291947b273