Migrate Sqlalchemy schema from mssql to sqlite db? - sqlite

Question

I have all my table classes written for mssql but now I want to test my application locally so I need sqlitedb.Is there a way through which I can Replicate my database in sqlite.
I am facing some issues like sqlite does not support Float as a Primary key.I have more than 200 tables I can not go and edit all just for testing.I can have all the tables in one metadata.
My idea is to use sqlite just for testing and for production I will still be using mssql.
Note I changed Float to Integer but still my tables are not created instead it just creates a empty db.
My code
for table in metadata.tables:
keys_to_change = []
for pkey_column in metadata.tables[table].primary_key.columns.keys():
keys_to_change.append(pkey_column)
for data in list(metadata.tables[table].foreign_keys):
keys_to_change.append(data.column.name)
for column in metadata.tables[table].columns:
if column.name in keys_to_change:
if str(column.type) == 'FLOAT':
column.type = INTEGER
engine = create_engine('sqlite:///mytest.db', echo=True, echo_pool=True)
metadata.create_all(engine)

Answer 1

If you are able to change the model code, I would suggest to create an alias to the Float and use it to define those primary_key and ForeignKey columns, which you could just change for your sqlite testing:
# CONFIGURATION
PKType = Float # default: MSSQL; or Float(N, M)
# PKType = Integer # uncomment this for sqlite
and your model becomes like below:
class MyParent(Base):
__tablename__ = 'my_parent'
id = Column(PKType, primary_key=True)
name = Column(String)
children = relationship('MyChild', backref='parent')
class MyChild(Base):
__tablename__ = 'my_child'
id = Column(PKType, primary_key=True)
parent_id = Column(PKType, ForeignKey('my_parent.id'))
name = Column(String)
Alternatively, if you would like to be only changing the engine and not another configuration variable, you can use dialect-specific custom type handling:
import sqlalchemy.types as types
class PKType(types.TypeDecorator):
impl = Float
def load_dialect_impl(self, dialect):
if dialect.name == 'sqlite':
return dialect.type_descriptor(Integer())
else:
return dialect.type_descriptor(Float())