def insert_or_ignore(model_cls, values, session=None):
"""Insert a new object into DB or ignore if it already exists.
This method is based on ability of MySQL, PostgreSQL and SQLite
to check unique constraint violations and allow user to take a
conflict mitigation action. Hence, uniqueness of the object that's
being inserted should be considered only from this perspective.
Note: This method hasn't been tested on databases other than MySQL,
PostgreSQL 9.5 or later, and SQLite. Therefore there's no guarantee
that it will work with them.
:param model_cls: Model class.
:param values: Values of the new object.
"""
model = model_cls()
model.update(values)
append = None
replace = None
dialect = b.get_dialect_name()
if dialect == 'sqlite':
replace = ('INSERT INTO', 'INSERT OR IGNORE INTO')
elif dialect == 'mysql':
append = 'ON DUPLICATE KEY UPDATE id=id'
elif dialect == 'postgres':
append = 'ON CONFLICT DO NOTHING'
else:
raise RuntimeError(
'"Insert or ignore" is supported only for dialects: sqlite,'
' mysql and postgres. Actual dialect: %s' % dialect
)
insert = model.__table__.insert(
append_string=append,
replace_string=replace
)
# NOTE(rakhmerov): As it turned out the result proxy object
# returned by insert expression does not provide a valid
# count of updated rows in for all supported databases.
# For this reason we shouldn't return anything from this
# method. In order to check whether a new object was really
# inserted users should rely on different approaches. The
# simplest is just to insert an object with an explicitly
# set id and then check if object with such id exists in DB.
# Generated id must be unique to make it work.
session.execute(insert, model.to_dict())
def insert_or_ignore(model_cls, values, session=None):
"""Insert a new object into DB or ignore if it already exists.
This method is based on ability of MySQL, PostgreSQL and SQLite
to check unique constraint violations and allow user to take a
conflict mitigation action. Hence, uniqueness of the object that's
being inserted should be considered only from this perspective.
Note: This method hasn't been tested on databases other than MySQL,
PostgreSQL 9.5 or later, and SQLite. Therefore there's no guarantee
that it will work with them.
:param model_cls: Model class.
:param values: Values of the new object.
"""
model = model_cls()
model.update(values)
append = None
replace = None
dialect = b.get_dialect_name()
if dialect == 'sqlite':
replace = ('INSERT INTO', 'INSERT OR IGNORE INTO')
elif dialect == 'mysql':
append = 'ON DUPLICATE KEY UPDATE id=id'
elif dialect == 'postgres':
append = 'ON CONFLICT DO NOTHING'
else:
raise RuntimeError(
'"Insert or ignore" is supported only for dialects: sqlite,'
' mysql and postgres. Actual dialect: %s' % dialect
)
insert = model.__table__.insert(
append_string=append,
replace_string=replace
)
# NOTE(rakhmerov): As it turned out the result proxy object
# returned by insert expression does not provide a valid
# count of updated rows in for all supported databases.
# For this reason we shouldn't return anything from this
# method. In order to check whether a new object was really
# inserted users should rely on different approaches. The
# simplest is just to insert an object with an explicitly
# set id and then check if object with such id exists in DB.
# Generated id must be unique to make it work.
session.execute(insert, model.to_dict())
