Naming convention for primary key and Flask, Sqlalchemy

[Gastón Avila]

Hi all,

I have set up specific naming conventions in a Flask-Sqlalchemy app using the metadata argument and it all seems to work except for naming PRIMARY KEY constraints. Here is what I have

self.db.init_app(app)
self.db.Model.metadata = MetaData(
 schema=self.app.config['SQLALCHEMY_DATABASE_SCHEMA'],
 naming_convention={
  "columns": columns,
  "ix": '%(table_name)s_%(columns)s_idx',
  "uq": "%(table_name)s_%(columns)s_key",
  "fk": "%(table_name)s_%(columns)s_fkey",
  "pk": "%(table_name)s_%(columns)s_pkey"
 }
)

and the columns helper is defined by:

def columns(constraint, table):
    return "_".join([col.name for col in constraint.columns])

It works for every single kind except for the primary key property of the naming convention obj. When printed out, the helper receives a constraint argument that when

print constraint

is added, gives PrimaryKeyConstraint() so no columns can be gotten from it.

Does anyone know what could be causing this? I have a guess that it might be this flask-sqlalchemy pluging but cannot figure it out.

Thanks a lot!

[Mike Bayer]

On 01/25/2016 02:51 PM, Gastón Avila wrote:
> Hi all,
>
> I have set up specific naming conventions in a Flask-Sqlalchemy app
> using the metadata argument and it all seems to work except for naming
> PRIMARY KEY constraints. Here is what I have
>
> |
> self.db.init_app(app)
> self.db.Model.metadata =MetaData(
> schema=self.app.config['SQLALCHEMY_DATABASE_SCHEMA'],
> naming_convention={
> "columns":columns,
> "ix":'%(table_name)s_%(columns)s_idx',
> "uq":"%(table_name)s_%(columns)s_key",
> "fk":"%(table_name)s_%(columns)s_fkey",
> "pk":"%(table_name)s_%(columns)s_pkey"
> }
> )
> |
>

> and the *columns* helper is defined by:
> |
> defcolumns(constraint,table):
> return"_".join([col.name forcol inconstraint.columns])
> |
>
> It works for every single kind except for the *primary key* property of

> the naming convention obj. When printed out, the helper receives a
> constraint argument that when
> |
> printconstraint
> |

> is added, gives *PrimaryKeyConstraint()* so no columns can be gotten
> from it.

Table makes its own PrimaryKeyConstraint up front and the naming
convention is not "deferred", that is the convention is called
immediately, so you'd need to specify a PrimaryKeyConstraint explicitly;
the good news is you can forego the "primary_key=True" flag within
columns when working this way:

def columns(constraint, table):
return "_".join([col.name for col in constraint.columns])

from sqlalchemy import MetaData, Integer, Column, Table, create_engine,
PrimaryKeyConstraint

m = MetaData(

naming_convention={
"columns": columns,
"ix": '%(table_name)s_%(columns)s_idx',
"uq": "%(table_name)s_%(columns)s_key",
"fk": "%(table_name)s_%(columns)s_fkey",
"pk": "%(table_name)s_%(columns)s_pkey"
}
)

t = Table('t', m, Column('id', Integer), PrimaryKeyConstraint('id'))

e = create_engine("sqlite://", echo=True)
m.create_all(e)

>
> Does anyone know what could be causing this? I have a guess that it
> might be this flask-sqlalchemy pluging but cannot figure it out.
>
> Thanks a lot!
>
>

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[Gastón J. Avila]

I had to use 

   __tablename__ = 'some_name'
   __table_args__ = (PrimaryKeyConstraint('id'), )

in my declarative models to get the same result.

Thanks Mike, that clears it all up.

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