# engine/mock.py
# Copyright (C) 2005-2024 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: https://www.opensource.org/licenses/mit-license.php
from operator import attrgetter
from . import base
from . import url as _url
from .. import util
from ..sql import ddl
class MockConnection(base.Connectable):
def __init__(self, dialect, execute):
self._dialect = dialect
self.execute = execute
engine = property(lambda s: s)
dialect = property(attrgetter("_dialect"))
name = property(lambda s: s._dialect.name)
def schema_for_object(self, obj):
return obj.schema
def connect(self, **kwargs):
return self
def execution_options(self, **kw):
return self
def compiler(self, statement, parameters, **kwargs):
return self._dialect.compiler(
statement, parameters, engine=self, **kwargs
)
def create(self, entity, **kwargs):
kwargs["checkfirst"] = False
ddl.SchemaGenerator(self.dialect, self, **kwargs).traverse_single(
entity
)
def drop(self, entity, **kwargs):
kwargs["checkfirst"] = False
ddl.SchemaDropper(self.dialect, self, **kwargs).traverse_single(entity)
def _run_ddl_visitor(
self, visitorcallable, element, connection=None, **kwargs
):
kwargs["checkfirst"] = False
visitorcallable(self.dialect, self, **kwargs).traverse_single(element)
def execute(self, object_, *multiparams, **params):
raise NotImplementedError()
def create_mock_engine(url, executor, **kw):
"""Create a "mock" engine used for echoing DDL.
This is a utility function used for debugging or storing the output of DDL
sequences as generated by :meth:`_schema.MetaData.create_all`
and related methods.
The function accepts a URL which is used only to determine the kind of
dialect to be used, as well as an "executor" callable function which
will receive a SQL expression object and parameters, which can then be
echoed or otherwise printed. The executor's return value is not handled,
nor does the engine allow regular string statements to be invoked, and
is therefore only useful for DDL that is sent to the database without
receiving any results.
E.g.::
from sqlalchemy import create_mock_engine
def dump(sql, *multiparams, **params):
print(sql.compile(dialect=engine.dialect))
engine = create_mock_engine('postgresql://', dump)
metadata.create_all(engine, checkfirst=False)
:param url: A string URL which typically needs to contain only the
database backend name.
:param executor: a callable which receives the arguments ``sql``,
``*multiparams`` and ``**params``. The ``sql`` parameter is typically
an instance of :class:`.DDLElement`, which can then be compiled into a
string using :meth:`.DDLElement.compile`.
.. versionadded:: 1.4 - the :func:`.create_mock_engine` function replaces
the previous "mock" engine strategy used with
:func:`_sa.create_engine`.
.. seealso::
:ref:`faq_ddl_as_string`
"""
# create url.URL object
u = _url.make_url(url)
dialect_cls = u.get_dialect()
dialect_args = {}
# consume dialect arguments from kwargs
for k in util.get_cls_kwargs(dialect_cls):
if k in kw:
dialect_args[k] = kw.pop(k)
# create dialect
dialect = dialect_cls(**dialect_args)
return MockConnection(dialect, executor)
