MySQL 8.0 SQLAlchemy suffix with SKIP LOCKED

mysql_8_skip_locked.py

# Use compiler extension to change SELECT FOR UPDATE with SKIP LOCKED, supported since MySQL 8.
# As of SQLAlchemy v1.2 SKIP LOCKED is only compiled for Oracle and PostgreSQL backends.
# ref: 
#  https://dev.mysql.com/doc/refman/8.0/en/innodb-locking-reads.html
#  https://docs.sqlalchemy.org/en/latest/core/selectable.html#sqlalchemy.sql.expression.Select.with_for_update

from sqlalchemy.ext.compiler import compiles
from sqlalchemy.sql.expression import Select
from sqlalchemy.sql.selectable import ForUpdateArg


@compiles(Select)
def suffix_skip_locked(select, compiler, **kw):
	for_update_clause = getattr(select, '_for_update_arg', None)
	if isinstance(for_update_clause, ForUpdateArg) and for_update_clause.skip_locked:
		return compiler.visit_select(select.suffix_with("SKIP LOCKED"), **kw)
	return compiler.visit_select(select, **kw)