Commit 967f9c05 authored by Jim Fulton's avatar Jim Fulton

Reenabled and moved check for conflicts on read to avoid reading

inconsistent data. Added a detailed comment with explanation.

Added explanation of the semantics for calling the function passed to
the storage tpc_finish method.
......@@ -84,8 +84,8 @@
##############################################################################
"""Database connection support
$Id: Connection.py,v 1.42 2001/01/15 15:49:29 chrism Exp $"""
__version__='$Revision: 1.42 $'[11:-2]
$Id: Connection.py,v 1.43 2001/01/15 18:49:49 jim Exp $"""
__version__='$Revision: 1.43 $'[11:-2]
from cPickleCache import PickleCache
from POSException import ConflictError, ExportError
......@@ -438,9 +438,22 @@ class Connection(ExportImport.ExportImport):
def setstate(self,object):
try:
oid=object._p_oid
#invalid=self._invalid
#if invalid(oid) or invalid(None): raise ConflictError, oid
p, serial = self._storage.load(oid, self._version)
# XXX this is quite conservative!
# We need, however, to avoid reading data from a transaction
# that committed after the current "session" started, as
# that might lead to mixing of cached data from earlier
# transactions and new inconsistent data.
#
# Note that we (carefully) wait until after we call the
# storage to make sure that we don't miss an invaildation
# notifications between the time we check and the time we
# read.
invalid=self._invalid
if invalid(oid) or invalid(None): raise ConflictError, oid
file=StringIO(p)
unpickler=Unpickler(file)
unpickler.persistent_load=self._persistent_load
......@@ -540,6 +553,13 @@ class Connection(ExportImport.ExportImport):
def tpc_finish(self, transaction):
# It's important that the storage call the function we pass
# (self.tpc_finish_) while it still has it's lock. We don't
# want another thread to be able to read any updated data
# until we've had a chance to send an invalidation message to
# all of the other connections!
self._storage.tpc_finish(transaction, self.tpc_finish_)
self._cache.invalidate(self._invalidated)
self._incrgc() # This is a good time to do some GC
......
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