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from sqlalchemy import schema, exceptions, util, sql, types
import StringIO, sys, re
import base, default
"""provides a thread-local transactional wrapper around the basic ComposedSQLEngine. multiple calls to engine.connect()
will return the same connection for the same thread. also provides begin/commit methods on the engine itself
which correspond to a thread-local transaction."""
class TLSession(object):
def __init__(self, engine):
self.engine = engine
self.__tcount = 0
def get_connection(self, close_with_result=False):
try:
return self.__transaction
except AttributeError:
return base.Connection(self.engine, close_with_result=close_with_result)
def begin(self):
if self.__tcount == 0:
self.__transaction = self.get_connection()
self.__trans = self.__transaction.begin()
self.__tcount += 1
def rollback(self):
if self.__tcount > 0:
try:
self.__trans.rollback()
finally:
del self.__transaction
del self.__trans
self.__tcount = 0
def commit(self):
if self.__tcount == 1:
try:
self._trans.commit()
finally:
del self.__transaction
del self._trans
self.__tcount = 0
elif self.__tcount > 1:
self.__tcount -= 1
def is_begun(self):
return self.__tcount > 0
class TLEngine(base.ComposedSQLEngine):
"""a ComposedSQLEngine that includes support for thread-local managed transactions. This engine
is better suited to be used with threadlocal Pool object."""
def __init__(self, *args, **kwargs):
"""the TLEngine relies upon the ConnectionProvider having "threadlocal" behavior,
so that once a connection is checked out for the current thread, you get that same connection
repeatedly."""
base.ComposedSQLEngine.__init__(self, *args, **kwargs)
self.context = util.ThreadLocal()
def raw_connection(self):
"""returns a DBAPI connection."""
return self.connection_provider.get_connection()
def connect(self, **kwargs):
"""returns a Connection that is not thread-locally scoped. this is the equilvalent to calling
"connect()" on a ComposedSQLEngine."""
return base.Connection(self, self.connection_provider.unique_connection())
def _session(self):
if not hasattr(self.context, 'session'):
self.context.session = TLSession(self)
return self.context.session
session = property(_session, doc="returns the current thread's TLSession")
def contextual_connect(self, **kwargs):
"""returns a TLConnection which is thread-locally scoped."""
return self.session.get_connection(**kwargs)
def begin(self):
return self.session.begin()
def commit(self):
self.session.commit()
def rollback(self):
self.session.rollback()
class TLocalConnectionProvider(default.PoolConnectionProvider):
def unique_connection(self):
return self._pool.unique_connection()
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