JezK
Edit File: mock.py
# engine/mock.py # Copyright (C) 2005-2023 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)