Current File : //opt/alt/python37/lib64/python3.7/site-packages/sqlalchemy/engine/strategies.py
# engine/strategies.py
# Copyright (C) 2005-2019 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
"""Strategies for creating new instances of Engine types.
These are semi-private implementation classes which provide the
underlying behavior for the "strategy" keyword argument available on
:func:`~sqlalchemy.engine.create_engine`. Current available options are
``plain``, ``threadlocal``, and ``mock``.
New strategies can be added via new ``EngineStrategy`` classes.
"""
from operator import attrgetter
from . import base
from . import threadlocal
from . import url
from .. import event
from .. import pool as poollib
from .. import util
from ..sql import schema
strategies = {}
class EngineStrategy(object):
"""An adaptor that processes input arguments and produces an Engine.
Provides a ``create`` method that receives input arguments and
produces an instance of base.Engine or a subclass.
"""
def __init__(self):
strategies[self.name] = self
def create(self, *args, **kwargs):
"""Given arguments, returns a new Engine instance."""
raise NotImplementedError()
class DefaultEngineStrategy(EngineStrategy):
"""Base class for built-in strategies."""
def create(self, name_or_url, **kwargs):
# create url.URL object
u = url.make_url(name_or_url)
plugins = u._instantiate_plugins(kwargs)
u.query.pop("plugin", None)
kwargs.pop("plugins", None)
entrypoint = u._get_entrypoint()
dialect_cls = entrypoint.get_dialect_cls(u)
if kwargs.pop("_coerce_config", False):
def pop_kwarg(key, default=None):
value = kwargs.pop(key, default)
if key in dialect_cls.engine_config_types:
value = dialect_cls.engine_config_types[key](value)
return value
else:
pop_kwarg = kwargs.pop
dialect_args = {}
# consume dialect arguments from kwargs
for k in util.get_cls_kwargs(dialect_cls):
if k in kwargs:
dialect_args[k] = pop_kwarg(k)
dbapi = kwargs.pop("module", None)
if dbapi is None:
dbapi_args = {}
for k in util.get_func_kwargs(dialect_cls.dbapi):
if k in kwargs:
dbapi_args[k] = pop_kwarg(k)
dbapi = dialect_cls.dbapi(**dbapi_args)
dialect_args["dbapi"] = dbapi
for plugin in plugins:
plugin.handle_dialect_kwargs(dialect_cls, dialect_args)
# create dialect
dialect = dialect_cls(**dialect_args)
# assemble connection arguments
(cargs, cparams) = dialect.create_connect_args(u)
cparams.update(pop_kwarg("connect_args", {}))
cargs = list(cargs) # allow mutability
# look for existing pool or create
pool = pop_kwarg("pool", None)
if pool is None:
def connect(connection_record=None):
if dialect._has_events:
for fn in dialect.dispatch.do_connect:
connection = fn(
dialect, connection_record, cargs, cparams
)
if connection is not None:
return connection
return dialect.connect(*cargs, **cparams)
creator = pop_kwarg("creator", connect)
poolclass = pop_kwarg("poolclass", None)
if poolclass is None:
poolclass = dialect_cls.get_pool_class(u)
pool_args = {"dialect": dialect}
# consume pool arguments from kwargs, translating a few of
# the arguments
translate = {
"logging_name": "pool_logging_name",
"echo": "echo_pool",
"timeout": "pool_timeout",
"recycle": "pool_recycle",
"events": "pool_events",
"use_threadlocal": "pool_threadlocal",
"reset_on_return": "pool_reset_on_return",
"pre_ping": "pool_pre_ping",
"use_lifo": "pool_use_lifo",
}
for k in util.get_cls_kwargs(poolclass):
tk = translate.get(k, k)
if tk in kwargs:
pool_args[k] = pop_kwarg(tk)
for plugin in plugins:
plugin.handle_pool_kwargs(poolclass, pool_args)
pool = poolclass(creator, **pool_args)
else:
if isinstance(pool, poollib.dbapi_proxy._DBProxy):
pool = pool.get_pool(*cargs, **cparams)
else:
pool = pool
pool._dialect = dialect
# create engine.
engineclass = self.engine_cls
engine_args = {}
for k in util.get_cls_kwargs(engineclass):
if k in kwargs:
engine_args[k] = pop_kwarg(k)
_initialize = kwargs.pop("_initialize", True)
# all kwargs should be consumed
if kwargs:
raise TypeError(
"Invalid argument(s) %s sent to create_engine(), "
"using configuration %s/%s/%s. Please check that the "
"keyword arguments are appropriate for this combination "
"of components."
% (
",".join("'%s'" % k for k in kwargs),
dialect.__class__.__name__,
pool.__class__.__name__,
engineclass.__name__,
)
)
engine = engineclass(pool, dialect, u, **engine_args)
if _initialize:
do_on_connect = dialect.on_connect()
if do_on_connect:
def on_connect(dbapi_connection, connection_record):
conn = getattr(
dbapi_connection, "_sqla_unwrap", dbapi_connection
)
if conn is None:
return
do_on_connect(conn)
event.listen(pool, "first_connect", on_connect)
event.listen(pool, "connect", on_connect)
def first_connect(dbapi_connection, connection_record):
c = base.Connection(
engine, connection=dbapi_connection, _has_events=False
)
c._execution_options = util.immutabledict()
dialect.initialize(c)
dialect.do_rollback(c.connection)
event.listen(pool, "first_connect", first_connect, once=True)
dialect_cls.engine_created(engine)
if entrypoint is not dialect_cls:
entrypoint.engine_created(engine)
for plugin in plugins:
plugin.engine_created(engine)
return engine
class PlainEngineStrategy(DefaultEngineStrategy):
"""Strategy for configuring a regular Engine."""
name = "plain"
engine_cls = base.Engine
PlainEngineStrategy()
class ThreadLocalEngineStrategy(DefaultEngineStrategy):
"""Strategy for configuring an Engine with threadlocal behavior."""
name = "threadlocal"
engine_cls = threadlocal.TLEngine
ThreadLocalEngineStrategy()
class MockEngineStrategy(EngineStrategy):
"""Strategy for configuring an Engine-like object with mocked execution.
Produces a single mock Connectable object which dispatches
statement execution to a passed-in function.
"""
name = "mock"
def create(self, name_or_url, executor, **kwargs):
# create url.URL object
u = url.make_url(name_or_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 kwargs:
dialect_args[k] = kwargs.pop(k)
# create dialect
dialect = dialect_cls(**dialect_args)
return MockEngineStrategy.MockConnection(dialect, executor)
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)
schema_for_object = schema._schema_getter(None)
def contextual_connect(self, **kwargs):
return self
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
from sqlalchemy.engine import ddl
ddl.SchemaGenerator(self.dialect, self, **kwargs).traverse_single(
entity
)
def drop(self, entity, **kwargs):
kwargs["checkfirst"] = False
from sqlalchemy.engine import ddl
ddl.SchemaDropper(self.dialect, self, **kwargs).traverse_single(
entity
)
def _run_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()
MockEngineStrategy()
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