> There are three calls of pysqlite_statement_reset() in _pysqlite_query_execute()

Yes, but only two before the cache is queried.

> So additional call of pysqlite_statement_reset() does not harm.

That's true, but removing redundant code makes it easier to read and maintain, IMO.

> On other hand removing it can introduce race condition.

How?

> Maybe the code could be rewritten in more explicit way and call pysqlite_statement_reset() only when it is necessary

Most of _pysqlite_query_execute() could be rewritten in order to make the code clearer. An alternative is to clean it up part by part.