SQLAlchemy create multi column index using naming_convention

Question

I am trying to create multi (i.e. 2-column index) for a model based table. But I'd like not to give specific name for this index. I'd like that naming_convention and alembic revision --autogenerate would do it's job with naming index. So far I have code like this:

from sqlalchemy import MetaData
from sqlalchemy.ext.declarative import as_declarative
from sqlalchemy.schema import Index

metadata = MetaData(
        naming_convention={
            'pk': '%(table_name)s_pk',
            'ix': '%(table_name)s_%(column_0_N_name)s_ix',
        },
    )

@as_declarative(metadata=metadata)
class Base:
    pass

class Foo(Base):
    id = Column(Integer, primary_key=True)
    col1 = Column('Col1', Integer)
    col2 = Column('Col2', DateTime)

Index(
    metadata.naming_convention['ix'] % {
        'table_name': Foo.__tablename__,
        'column_0_N_name': Foo.col1.expression.name + "_" + Foo.col2.expression.name
    },
    Foo.col1,
    Foo.col2,
)

So I'd like to avoid the 'creating name' part of code:

    metadata.naming_convention['ix'] % {
        'table_name': Foo.__tablename__,
        'column_0_N_name': Foo.col1.expression.name + "_" + Foo.col2.expression.name
    }

Answer 1

after more search there is very simple solution. According to github comment in SQLAlchemy issue if you would like to create index by Index() you silmply need to pass name=None argument, and fill arguments for columns.

so the code above should look like (part that stays the same):

from sqlalchemy import MetaData
from sqlalchemy.ext.declarative import as_declarative
from sqlalchemy.schema import Index

metadata = MetaData(
        naming_convention={
            'pk': '%(table_name)s_pk',
            'ix': '%(table_name)s_%(column_0_N_name)s_ix',
        },
    )

@as_declarative(metadata=metadata)
class Base:
    pass

Option 1 (declare multi column index out of table model)

class Foo(Base):
    id = Column(Integer, primary_key=True)
    col1 = Column('Col1', Integer)
    col2 = Column('Col2', DateTime)

Index(None, Foo.col1, Foo.col2)

Option 2 (declare multi column index inside of table model)

class Foo(Base):
    id = Column(Integer, primary_key=True)
    col1 = Column('Col1', Integer)
    col2 = Column('Col2', DateTime)
    __table_args__ = (
        Index(None, 'Col1', 'Col2'),
    )

Then index name (in both options) would be:

Foo_Col1_Col2_ix

I have not found this kind of solution in SQLALchemy documentation (maybe there is?), but it's good that there are some answers on github issues in SQLAlchemy github :)