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119 lines
3.5 KiB
119 lines
3.5 KiB
# engine/mock.py
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# Copyright (C) 2005-2022 the SQLAlchemy authors and contributors
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# <see AUTHORS file>
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#
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# This module is part of SQLAlchemy and is released under
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# the MIT License: https://www.opensource.org/licenses/mit-license.php
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from operator import attrgetter
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from . import base
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from . import url as _url
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from .. import util
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from ..sql import ddl
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class MockConnection(base.Connectable):
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def __init__(self, dialect, execute):
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self._dialect = dialect
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self.execute = execute
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engine = property(lambda s: s)
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dialect = property(attrgetter("_dialect"))
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name = property(lambda s: s._dialect.name)
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def schema_for_object(self, obj):
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return obj.schema
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def connect(self, **kwargs):
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return self
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def execution_options(self, **kw):
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return self
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def compiler(self, statement, parameters, **kwargs):
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return self._dialect.compiler(
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statement, parameters, engine=self, **kwargs
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)
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def create(self, entity, **kwargs):
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kwargs["checkfirst"] = False
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ddl.SchemaGenerator(self.dialect, self, **kwargs).traverse_single(
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entity
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)
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def drop(self, entity, **kwargs):
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kwargs["checkfirst"] = False
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ddl.SchemaDropper(self.dialect, self, **kwargs).traverse_single(entity)
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def _run_ddl_visitor(
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self, visitorcallable, element, connection=None, **kwargs
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):
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kwargs["checkfirst"] = False
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visitorcallable(self.dialect, self, **kwargs).traverse_single(element)
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def execute(self, object_, *multiparams, **params):
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raise NotImplementedError()
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def create_mock_engine(url, executor, **kw):
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"""Create a "mock" engine used for echoing DDL.
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This is a utility function used for debugging or storing the output of DDL
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sequences as generated by :meth:`_schema.MetaData.create_all`
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and related methods.
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The function accepts a URL which is used only to determine the kind of
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dialect to be used, as well as an "executor" callable function which
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will receive a SQL expression object and parameters, which can then be
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echoed or otherwise printed. The executor's return value is not handled,
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nor does the engine allow regular string statements to be invoked, and
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is therefore only useful for DDL that is sent to the database without
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receiving any results.
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E.g.::
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from sqlalchemy import create_mock_engine
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def dump(sql, *multiparams, **params):
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print(sql.compile(dialect=engine.dialect))
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engine = create_mock_engine('postgresql://', dump)
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metadata.create_all(engine, checkfirst=False)
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:param url: A string URL which typically needs to contain only the
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database backend name.
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:param executor: a callable which receives the arguments ``sql``,
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``*multiparams`` and ``**params``. The ``sql`` parameter is typically
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an instance of :class:`.DDLElement`, which can then be compiled into a
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string using :meth:`.DDLElement.compile`.
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.. versionadded:: 1.4 - the :func:`.create_mock_engine` function replaces
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the previous "mock" engine strategy used with
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:func:`_sa.create_engine`.
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.. seealso::
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:ref:`faq_ddl_as_string`
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"""
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# create url.URL object
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u = _url.make_url(url)
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dialect_cls = u.get_dialect()
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dialect_args = {}
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# consume dialect arguments from kwargs
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for k in util.get_cls_kwargs(dialect_cls):
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if k in kw:
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dialect_args[k] = kw.pop(k)
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# create dialect
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dialect = dialect_cls(**dialect_args)
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return MockConnection(dialect, executor)
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