sqlalchemy-to-ormar

A simple auto-translator from sqlalchemy ORM models to ormar models.

The ormar package is an async mini ORM for Python, with support for Postgres, MySQL, and SQLite.

To learn more about ormar:

• ormar github
• ormar documentation

Quickstart

fromdatabasesimportDatabasefromsqlalchemyimport (
Column,
ForeignKey,
Integer,
MetaData,
String,
create_engine,
DECIMAL,
)
fromsqlalchemy.ext.declarativeimportdeclarative_basefromsqlalchemy.ormimportSession, relationship, sessionmakerBase=declarative_base()
Database_URL="sqlite:///test.db"engine=create_engine(Database_URL, echo=True)
# given sqlalchemy models you already haveclassUser(Base):
__tablename__="users"id=Column(Integer, primary_key=True)
name=Column(String)
fullname=Column(String)
nickname=Column(String)
salary=Column(DECIMAL)
addresses=relationship(
"Address", back_populates="user", cascade="all, delete, delete-orphan"
)
classAddress(Base):
__tablename__="addresses"id=Column(Integer, primary_key=True)
email_address=Column(String, nullable=False)
user_id=Column(Integer, ForeignKey("users.id"))
user=relationship("User", back_populates="addresses")
# instantiate new Databases instancedatabase=Database(Database_URL)
# note that you need new metadata instance as table names in ormar# will remain the same and you cannot have two tables with same name in# one metadata, note that we bind it to the same engine! # (or you can create new one with same url) metadata=MetaData(engine)
# use sqlalchemy-to-ormar (not normally imports should be at the top)fromsqlalchemy_to_ormarimportormar_model_str_repr, sqlalchemy_to_ormar# convert sqlalchemy models to ormarOrmarAddress=sqlalchemy_to_ormar(Address, database=database, metadata=metadata)
OrmarUser=sqlalchemy_to_ormar(User, database=database, metadata=metadata)
# you can print the ormar model# or save it to file and you have proper model definition created for youaddress_str=ormar_model_str_repr(OrmarAddress)
# now you can print it or save to fileprint(address_str)
# will print:# class OrmarAddress(ormar.Model):# # class Meta(ormar.ModelMeta):# metadata=metadata# database=database# tablename="addresses"# # id = ormar.Integer(autoincrement=True, primary_key=True)# email_address = ormar.String(max_length=255, nullable=False)# user = ormar.ForeignKey(to=OrmarUser, related_name="addresses", name=user_id, nullable=True)# if you want to skip column aliases if they match field names use skip_names_if_match flaguser_model_str=ormar_model_str_repr(OrmarUser, skip_names_if_match=True)
# let's insert some sample data with sync sqlalchemyBase.metadata.create_all(engine)
LocalSession=sessionmaker(bind=engine)
db: Session=LocalSession()
ed_user=User(name="ed", fullname="Ed Jones", nickname="edsnickname")
address=Address(email_address="ed@example.com")
address2=Address(email_address="eddy@example.com")
ed_user.addresses= [address, address2]
db.add(ed_user)
db.commit()
# and now we can query it asynchronously with ormarasyncdeftest_ormar_queries(): user=awaitOrmarUser.objects.select_related("addresses").get(name='ed')
assertlen(user.addresses) ==2assertuser.nickname=='edsnickname'assertuser.fullname=='Ed Jones'addresses=awaitOrmarAddress.objects.select_related('user').all(user__name='ed')
assertlen(addresses) ==2assertaddresses[0].user.nickname=='edsnickname'assertaddresses[1].user.nickname=='edsnickname'# run asyncimportasyncioasyncio.run(test_ormar_queries())
# drop dbBase.metadata.drop_all(engine)

Automap support

You can use sqlacodegen to generate sqlalchemy models out of existing database and then use sqlalchemy-to-ormar to translate it to ormar models.

Note that sqlalchemy has it's own automap feature, but out of experience it does not work well with complicated databases.

Supported fields

sqlalchemy-to-ormar supports following sqlalchemy field types:

• "integer": ormar.Integer,
• "small_integer": ormar.Integer,
• "big_integer": ormar.BigInteger,
• "string": ormar.String,
• "text": ormar.Text,
• "float": ormar.Float,
• "decimal": ormar.Decimal,
• "date": ormar.Date,
• "datetime": ormar.DateTime,
• "time": ormar.Time,
• "boolean": ormar.Boolean

Supported relations

sqlalchemy-to-ormar supports both ForeignKey as well as ManyToMany relations although like ormar itself it will create relation field on one side of the relation only and other side will be auto-populated with reversed side.

Known limitations

sqlalchemy to ormar right now does not support:

• composite (multi-column) primary keys and foreign keys (as ormar does not support them yet)
• cascade options from relationship are ignored, only the ones declared in sqlalchemy ForeignKey (ondelete, onupdate) are extracted
• ManyToMany fields names customization (as ormar does not support them yet)
• ManyToMany association table has to have primary key
• Model inheritance