Create and check schema on ORM

[Dmitry Tyutryumov]

Hi guys, i need you help.

How i can create a schema on ORM, for few tables,

• MetaData doesn't work when schema doesn't exist.

• event.listen(DeclBase.metadata, 'before_create', CreateSchema('schema')) i see an error if schema is exist, but i don't know how to check schema on ORM

Will be appreciate for help

[Mike Bayer]

hello -

you'd need to either run the appropriate SQL to detect if this schema exists (this is database dependent, see http://docs.sqlalchemy.org/en/latest/core/ddl.html#controlling-ddl-sequences for an example), or just emit the statement "CREATE SCHEMA IF NOT EXISTS <foobar>":

from sqlalchemy import MetaData, Integer, Table, Column, event, create_engine
from sqlalchemy.schema import CreateSchema
from sqlalchemy import exc

m = MetaData()

t = Table(
    't', m, Column('x', Integer),
    schema="some_schema"
)


def should_create(ddl, target, connection, **kw):
    try:
        connection.execute(
            "SHOW CREATE SCHEMA %s" %
            ddl.element).scalar()
        return False
    except exc.DBAPIError:
        return True

event.listen(
    m, "before_create",
    CreateSchema("some_schema").execute_if(
        callable_=should_create
    )
)


e = create_engine("mysql://scott:tiger@localhost/test", echo=True)

m.create_all(e)

[Mike Bayer]

Duplicate of #2843.

[Dmitry Tyutryumov]

Thank you for help