Initial Configuration Push

deps/sqlalchemy/engine/strategies.py

@@ -0,0 +1,262 @@
+# engine/strategies.py
+# Copyright (C) 2005-2016 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 sqlalchemy.engine import base, threadlocal, url
+from sqlalchemy import util, exc, event
+from sqlalchemy import pool as poollib
+
+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)
+
+        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
+
+        # 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 = {}
+
+            # 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'}
+            for k in util.get_cls_kwargs(poolclass):
+                tk = translate.get(k, k)
+                if tk in kwargs:
+                    pool_args[k] = pop_kwarg(tk)
+            pool = poolclass(creator, **pool_args)
+        else:
+            if isinstance(pool, poollib._DBProxy):
+                pool = pool.get_pool(*cargs, **cparams)
+            else:
+                pool = pool
+
+        # 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)
+            event.listen(pool, 'first_connect', first_connect, once=True)
+
+        dialect_cls.engine_created(engine)
+        if entrypoint is not dialect_cls:
+            entrypoint.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)
+
+        def contextual_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()