allow no whitespaces between VALUES and ( when do bulk insert/replace

[uwydoc]

the regular expression used to check whether bulk insert/replace is possible is as follows:

RE_INSERT_VALUES = re.compile(
    r"\s*((?:INSERT|REPLACE)\s.+\sVALUES?\s+)" +
    r"(\(\s*(?:%s|%\(.+\)s)\s*(?:,\s*(?:%s|%\(.+\)s)\s*)*\))" +
    r"(\s*(?:ON DUPLICATE.*)?);?\s*\Z",
    re.IGNORECASE | re.DOTALL)

notice the last \s+ in the first part of the regular expression requires whitespaces between VALUES and left-parenthesis, which means queries like insert into user values(%s, %s) would not be considered bulk-insertable. although the demo sql query in the comment of executemany has a space between VALUES and (, i do think this restriction could be relaxed.

This gotcha is so trivial and would cost some time to realize. It actually costed me some time to find out why the performance of a relatively simple program dropped by more than 6 times after switching from MySQLdb to PyMySQL.

The fix is quite simple, just replace the \s+ with \s* in the first part.

NOTE: ported from PyMySQL/mysqlclient@354dcb5

[methane]

Please copy this commit:
PyMySQL/mysqlclient@354dcb5

[uwydoc]

@methane done and thanks.