258 lines
8.5 KiB
Python
258 lines
8.5 KiB
Python
# engine/strategies.py
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# Copyright (C) 2005-2014 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 sqlalchemy.engine import base, threadlocal, url
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from sqlalchemy import util, exc, event
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from sqlalchemy import pool as poollib
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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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dialect_cls = u.get_dialect()
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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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# 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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# 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():
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try:
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return dialect.connect(*cargs, **cparams)
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except dialect.dbapi.Error as e:
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invalidated = dialect.is_disconnect(e, None, None)
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util.raise_from_cause(
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exc.DBAPIError.instance(
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None, None, e, dialect.dbapi.Error,
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connection_invalidated=invalidated
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)
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)
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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 = {}
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# consume pool arguments from kwargs, translating a few of
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# the arguments
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translate = {'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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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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pool = poolclass(creator, **pool_args)
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else:
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if isinstance(pool, poollib._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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# 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." % (','.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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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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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(engine, connection=dbapi_connection,
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_has_events=False)
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dialect.initialize(c)
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event.listen(pool, 'first_connect', first_connect, once=True)
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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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def contextual_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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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(
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self.dialect, self, **kwargs).traverse_single(entity)
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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(
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self.dialect, self, **kwargs).traverse_single(entity)
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def _run_visitor(self, visitorcallable, element,
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connection=None,
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**kwargs):
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kwargs['checkfirst'] = False
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visitorcallable(self.dialect, self,
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**kwargs).traverse_single(element)
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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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