How to customize base declarative class to add naming conventions

[rdeb...@gmail.com]

I'd like to create a mixin to specify naming conventions.

I tried both:

class Base:
    metadata = MetaData(naming_convention={
        "ix": "ix_%(column_0_label)s",
        "uq": "uq_%(table_name)s_%(column_0_name)s",
        "ck": "ck_%(table_name)s_%(constraint_name)s",
        "fk": "fk_%(table_name)s_%(column_0_name)s_%(referred_table_name)s",
        "pk": "pk_%(table_name)",
    })

and

class Base:
    @declared_attr
    def metadata(cls):
        return MetaData(naming_convention={
            "ix": "ix_%(column_0_label)s",
            "uq": "uq_%(table_name)s_%(column_0_name)s",
            "ck": "ck_%(table_name)s_%(constraint_name)s",
            "fk": "fk_%(table_name)s_%(column_0_name)s_%(referred_table_name)s",
            "pk": "pk_%(table_name)",
        })

But if I inspect a model created using this base I always got:

>>> Test.metadata.naming_convention
immutabledict({'ix': 'ix_%(column_0_label)s'})

while I correctly have:

>>> Base.metadata.naming_convention

{'ix': 'ix_%(column_0_label)s',
 'uq': 'uq_%(table_name)s_%(column_0_name)s',
 'ck': 'ck_%(table_name)s_%(constraint_name)s',
 'fk': 'fk_%(table_name)s_%(column_0_name)s_%(referred_table_name)s',
 'pk': 'pk_%(table_name)'}

What is the correct way to do it? what am i doing wrong? Should I do this in my migration tool (alembic) ?

Also would it works for unique constraint on multiple column or do we have to name them explicitly.

Thanks a lot!

[Simon King]

Is it important to you to do this via a mixin? declarative_base
accepts a "metadata" parameter, so something like this should work:

metadata = MetaData(naming_convention={...})
Base = declarative_base(metadata=metadata)

Hope that helps,

Simon

[René-paul Debroize]

It would have been great to be able to do it via a mixin, I have several DB using decalarative base constructed with this Base mixin and I liked to have the same naming_convention for all the DBs without repeating myself.

If it's not I guess i can still manage to find an acceptable way of doing it using the decalarative_base arg.

Thanks.

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[Derek Lambert]

Just define the naming convention dict in a separate file and import it into each declarative base?