Proper syntax for __table_args__ ?

[Don O'Hara]

I'm looking for advice on best SA coding practices to accomplish:

1. Use bind keys

2. Add user-defined tags to tables, to allow iterating through the metadata later to find tables with those tags.

3. Use base table classes for common attributes and methods

Is there a chance that class member names will get mangled in derived classes,

and cause problems somewhere downstream? The code works now, but when I remove one of the

base classes, and code the metadata directly in the table class things break.

I'd like to get  a better understanding of how it all fits, and make sure I'm setting things up correctly.

Thanks,

Don

My code:

in config.py

SQLALCHEMY_BINDS = {
    'api': 'postgresql+psycopg2://oharad:dino@localhost:5432/dev_api_02',
    'person_indexes': 'postgresql+psycopg2://oharad:dino@localhost:5432/dev_person_ix_01',
    'analysis_result': 'postgresql+psycopg2://oharad:dino@localhost:5432/dev_analysis_res_01'
}

in models/__init__.py

ACCOUNT_SCHEMA_NAMESPACE = 'account'

class BaseAppTable(db.Model):

    __abstract__ = True

    def to_json(self):

        json = {c.name: str(getattr(self, c.name)) or '' for c in self.__table__.columns}

        return json

in models/account.py

from models import BaseAppTable, db, ACCOUNT_SCHEMA_NAMESPACE

_BASE_TABLE_ARGS = {'info': {'table_namespace': ACCOUNT_SCHEMA_NAMESPACE}}

class BaseAccountTable(object):

  __bind_key__ = 'api'

  __table_args__ = _BASE_TABLE_ARGS

class Account(BaseAppTable, BaseAccountTable):

    __tablename__ = "account"

    #

    # need to explicitly code __table_args__ here to use 'tuple, dict' syntax

    __table_args__ = (UniqueConstraint('name', 'company_id', name='account_uq_ix1'), 

                      _BASE_TABLE_ARGS)

    account_id = db.Column(db.Integer, primary_key=True)

    name = db.Column(db.String(length=50), nullable=False)

    company_id = db.Column(db.Integer, db.ForeignKey('global.company.company_id'), nullable=False)

class RoleGroup(BaseAppTable, BaseAccountTable):

    __tablename__ = "role_group"

    role_group_id = db.Column(UUID, primary_key=True)

    type_code = db.Column(db.SmallInteger, nullable=False)

    name = db.Column(db.String(length=100), nullable=False, unique=True)

This code works fine, but I'm worried something might break due to name mangling.

When I change the code to avoid base classes, I get an error:

class AccountCodeNamespace(BaseAppTable):
  __tablename__ = "account_code_namespace"
  __table_args__ = _BASE_TABLE_ARGS
  __bind_key__ = 'api'

  #  AssertionError: Bind 'api' is not specified.  Set it in the SQLALCHEMY_BINDS configuration variable

[Mike Bayer]

On 10/13/15 7:16 AM, Don O'Hara wrote:
> I'm looking for advice on best SA coding practices to accomplish:
>
> 1. Use bind keys

I'm not familiar with that, I see you using something called
__bind_key__ and SQLALCHEMY_BINDS. These are not constructs that are
part of SQLAlchemy; if this is a third-party package of some kind, I'd
ask them for help.

> 2. Add user-defined tags to tables, to allow iterating through the
> metadata later to find tables with those tags.
> 3. Use base table classes for common attributes and methods
>
> Is there a chance that class member names will get mangled in derived
> classes,
> and cause problems somewhere downstream? The code works now, but when I
> remove one of the
> base classes, and code the metadata directly in the table class things
> break.
>
> I'd like to get a better understanding of how it all fits, and make
> sure I'm setting things up correctly.
>
> Thanks,
> Don
>
>
>
> My code:
>
> |

> _inconfig.__py
> _

> SQLALCHEMY_BINDS ={
> 'api':'postgresql+psycopg2://oharad:dino@localhost:5432/dev_api_02',
>
> 'person_indexes':'postgresql+psycopg2://oharad:dino@localhost:5432/dev_person_ix_01',
>
> 'analysis_result':'postgresql+psycopg2://oharad:dino@localhost:5432/dev_analysis_res_01'
> }
>

> _in models/__init__.py_

>
> ACCOUNT_SCHEMA_NAMESPACE = 'account'
>
> class BaseAppTable(db.Model):
> __abstract__ = True
> def to_json(self):
> json = {c.name: str(getattr(self, c.name)) or '' for c in
> self.__table__.columns}
> return json
>
>

> _in models/account.py_

> * # AssertionError: Bind 'api' is not specified. Set it in the
> SQLALCHEMY_BINDS configuration variable*
>
>
>
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[Don O'Hara]

Oops - should have asked the Flask-SQLAlchemy folks!

Thanks

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