320 lines
9.6 KiB
Python
320 lines
9.6 KiB
Python
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# engine/strategies.py
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# Copyright (C) 2005-2019 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: http://www.opensource.org/licenses/mit-license.php
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"""Strategies for creating new instances of Engine types.
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These are semi-private implementation classes which provide the
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underlying behavior for the "strategy" keyword argument available on
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:func:`~sqlalchemy.engine.create_engine`. Current available options are
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``plain``, ``threadlocal``, and ``mock``.
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New strategies can be added via new ``EngineStrategy`` classes.
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"""
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from operator import attrgetter
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from . import base
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from . import threadlocal
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from . import url
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from .. import event
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from .. import pool as poollib
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from .. import util
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from ..sql import schema
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strategies = {}
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class EngineStrategy(object):
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"""An adaptor that processes input arguments and produces an Engine.
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Provides a ``create`` method that receives input arguments and
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produces an instance of base.Engine or a subclass.
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"""
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def __init__(self):
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strategies[self.name] = self
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def create(self, *args, **kwargs):
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"""Given arguments, returns a new Engine instance."""
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raise NotImplementedError()
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class DefaultEngineStrategy(EngineStrategy):
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"""Base class for built-in strategies."""
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def create(self, name_or_url, **kwargs):
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# create url.URL object
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u = url.make_url(name_or_url)
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plugins = u._instantiate_plugins(kwargs)
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u.query.pop("plugin", None)
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kwargs.pop("plugins", None)
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entrypoint = u._get_entrypoint()
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dialect_cls = entrypoint.get_dialect_cls(u)
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if kwargs.pop("_coerce_config", False):
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def pop_kwarg(key, default=None):
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value = kwargs.pop(key, default)
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if key in dialect_cls.engine_config_types:
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value = dialect_cls.engine_config_types[key](value)
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return value
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else:
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pop_kwarg = kwargs.pop
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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 kwargs:
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dialect_args[k] = pop_kwarg(k)
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dbapi = kwargs.pop("module", None)
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if dbapi is None:
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dbapi_args = {}
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for k in util.get_func_kwargs(dialect_cls.dbapi):
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if k in kwargs:
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dbapi_args[k] = pop_kwarg(k)
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dbapi = dialect_cls.dbapi(**dbapi_args)
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dialect_args["dbapi"] = dbapi
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for plugin in plugins:
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plugin.handle_dialect_kwargs(dialect_cls, dialect_args)
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# create dialect
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dialect = dialect_cls(**dialect_args)
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# assemble connection arguments
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(cargs, cparams) = dialect.create_connect_args(u)
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cparams.update(pop_kwarg("connect_args", {}))
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cargs = list(cargs) # allow mutability
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# look for existing pool or create
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pool = pop_kwarg("pool", None)
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if pool is None:
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def connect(connection_record=None):
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if dialect._has_events:
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for fn in dialect.dispatch.do_connect:
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connection = fn(
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dialect, connection_record, cargs, cparams
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)
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if connection is not None:
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return connection
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return dialect.connect(*cargs, **cparams)
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creator = pop_kwarg("creator", connect)
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poolclass = pop_kwarg("poolclass", None)
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if poolclass is None:
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poolclass = dialect_cls.get_pool_class(u)
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pool_args = {"dialect": dialect}
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# consume pool arguments from kwargs, translating a few of
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# the arguments
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translate = {
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"logging_name": "pool_logging_name",
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"echo": "echo_pool",
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"timeout": "pool_timeout",
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"recycle": "pool_recycle",
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"events": "pool_events",
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"use_threadlocal": "pool_threadlocal",
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"reset_on_return": "pool_reset_on_return",
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"pre_ping": "pool_pre_ping",
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"use_lifo": "pool_use_lifo",
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}
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for k in util.get_cls_kwargs(poolclass):
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tk = translate.get(k, k)
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if tk in kwargs:
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pool_args[k] = pop_kwarg(tk)
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for plugin in plugins:
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plugin.handle_pool_kwargs(poolclass, pool_args)
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pool = poolclass(creator, **pool_args)
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else:
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if isinstance(pool, poollib.dbapi_proxy._DBProxy):
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pool = pool.get_pool(*cargs, **cparams)
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else:
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pool = pool
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pool._dialect = dialect
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# create engine.
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engineclass = self.engine_cls
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engine_args = {}
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for k in util.get_cls_kwargs(engineclass):
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if k in kwargs:
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engine_args[k] = pop_kwarg(k)
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_initialize = kwargs.pop("_initialize", True)
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# all kwargs should be consumed
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if kwargs:
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raise TypeError(
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"Invalid argument(s) %s sent to create_engine(), "
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"using configuration %s/%s/%s. Please check that the "
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"keyword arguments are appropriate for this combination "
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"of components."
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% (
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",".join("'%s'" % k for k in kwargs),
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dialect.__class__.__name__,
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pool.__class__.__name__,
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engineclass.__name__,
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)
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)
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engine = engineclass(pool, dialect, u, **engine_args)
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if _initialize:
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do_on_connect = dialect.on_connect()
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if do_on_connect:
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def on_connect(dbapi_connection, connection_record):
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conn = getattr(
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dbapi_connection, "_sqla_unwrap", dbapi_connection
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)
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if conn is None:
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return
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do_on_connect(conn)
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event.listen(pool, "first_connect", on_connect)
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event.listen(pool, "connect", on_connect)
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def first_connect(dbapi_connection, connection_record):
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c = base.Connection(
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engine, connection=dbapi_connection, _has_events=False
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)
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c._execution_options = util.immutabledict()
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dialect.initialize(c)
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dialect.do_rollback(c.connection)
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event.listen(
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pool,
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"first_connect",
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first_connect,
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_once_unless_exception=True,
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)
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dialect_cls.engine_created(engine)
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if entrypoint is not dialect_cls:
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entrypoint.engine_created(engine)
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for plugin in plugins:
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plugin.engine_created(engine)
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return engine
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class PlainEngineStrategy(DefaultEngineStrategy):
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"""Strategy for configuring a regular Engine."""
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name = "plain"
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engine_cls = base.Engine
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PlainEngineStrategy()
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class ThreadLocalEngineStrategy(DefaultEngineStrategy):
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"""Strategy for configuring an Engine with threadlocal behavior."""
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name = "threadlocal"
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engine_cls = threadlocal.TLEngine
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ThreadLocalEngineStrategy()
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class MockEngineStrategy(EngineStrategy):
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"""Strategy for configuring an Engine-like object with mocked execution.
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Produces a single mock Connectable object which dispatches
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statement execution to a passed-in function.
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"""
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name = "mock"
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def create(self, name_or_url, executor, **kwargs):
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# create url.URL object
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u = url.make_url(name_or_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 kwargs:
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dialect_args[k] = kwargs.pop(k)
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# create dialect
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dialect = dialect_cls(**dialect_args)
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return MockEngineStrategy.MockConnection(dialect, executor)
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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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schema_for_object = schema._schema_getter(None)
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def contextual_connect(self, **kwargs):
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return self
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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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from sqlalchemy.engine import ddl
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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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from sqlalchemy.engine import ddl
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ddl.SchemaDropper(self.dialect, self, **kwargs).traverse_single(
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entity
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)
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def _run_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(
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element
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)
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def execute(self, object_, *multiparams, **params):
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raise NotImplementedError()
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MockEngineStrategy()
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