Cross database join

[RealJTG]

Is it possible to perform cross database join somehow on the same MySQL instance? For example:

SELECT A.value, B.value
FROM db1.foo A 
JOIN db2.bar B ON A.id = B.id

[coleifer]

Interesting. Peewee does not support this out of the box, so your best option right now is to probably use the RawQuery helper (docs).

Another option is to take a look at how the PostgresqlDatabase supports a "schema" argument. The schema is only used to prefix table and column names, so maybe it could be repurposed to prefix with the database name instead?

[RealJTG]

schema seems to work fine. I'm using flask-peewee and my DB class now looks like this (with delayed initialization coleifer/flask-peewee#154 and multiple configurations support)

class SchemaProxy(object):
    __slots__ = ['obj']

    def __init__(self):
        self.initialize(None)

    def initialize(self, obj):
        self.obj = obj

    def __str__(self):
        return self.obj or None


class ConfigurableDatabase(Database):

    def __init__(self, app=None, config_key='DATABASE'):
        self.config_key = config_key
        self.schema = SchemaProxy()
        super(ConfigurableDatabase, self).__init__(app)

    def load_database(self):
        self.database_config = dict(self.app.config[self.config_key])
        try:
            self.database_name = self.database_config.pop('name')
            self.database_engine = self.database_config.pop('engine')
            self.schema.initialize(self.database_name)
        except KeyError:
            raise ImproperlyConfigured('Please specify a "name" and "engine" for your database')

        try:
            self.database_class = load_class(self.database_engine)
            assert issubclass(self.database_class, PeeweeDatabase)
        except ImportError:
            raise ImproperlyConfigured('Unable to import: "%s"' % self.database_engine)
        except AttributeError:
            raise ImproperlyConfigured('Database engine not found: "%s"' % self.database_engine)
        except AssertionError:
            raise ImproperlyConfigured('Database engine not a subclass of peewee.Database: "%s"' % self.database_engine)

        self.database = self.database_class(self.database_name, **self.database_config)

    def get_model_class(self):
        class BaseModel(Model):
            class Meta:
                database = self.proxy
                schema = self.schema

        return BaseModel

With werkzeug.local.LocalProxy even cleaner, but not sure about side effects

class ConfigurableDatabase(Database):

    def get_model_class(self):
        class BaseModel(Model):
            class Meta:
                database = self.proxy
                schema = LocalProxy(lambda: self.database_name)

        return BaseModel

[coleifer]

Neat. I'm going to close as it sounds like your immediate issue is resolved. Please comment if this is not the case.