first draft for a simple hooks based custom attribute storage,
with a BytesFileSystemStorage POC implementation.
Basically:
* a dictionary contains maps from which attribute of which entity types are
mapped to which custom storage
* hooks check for one of these entity type being added/modified/deleted
* read is based on the sql generator callback mecanism (used in vcsfile for
instance)
* all storages have the same basic interface (read, add, update, delete),
and should be pluggable in a transparent way (except at migration time
when one want to change from a storage to another)
* the sample BytesFileSystemStorage:
* may store Bytes attributes content of any entity type as file on the file system
* is based on one FSPATH rql/sql function and another _fsopen only available in sql
* has a dumb file name allocation algorithm
"""hooks to handle attributes mapped to a custom storage
"""
from os import unlink
from cubicweb.server.hook import Hook
from cubicweb.server.sources.storages import ETYPE_ATTR_STORAGE
class BFSSHook(Hook):
"""abstract class for bytes file-system storage hooks"""
__abstract__ = True
category = 'bfss'
class PreAddEntityHook(BFSSHook):
""""""
__regid__ = 'bfss_add_entity'
events = ('before_add_entity', )
#__select__ = Hook.__select__ & implements('Repository')
def __call__(self):
for attr in ETYPE_ATTR_STORAGE.get(self.entity.__regid__, ()):
fpath = ETYPE_ATTR_STORAGE[self.entity.__regid__][attr].entity_added(self.entity, attr)
if fpath is not None:
AddFileOp(filepath=fpath)
class PreUpdateEntityHook(BFSSHook):
""""""
__regid__ = 'bfss_update_entity'
events = ('before_update_entity', )
#__select__ = Hook.__select__ & implements('Repository')
def __call__(self):
for attr in ETYPE_ATTR_STORAGE.get(self.entity.__regid__, ()):
ETYPE_ATTR_STORAGE[self.entity.__regid__][attr].entity_updated(self.entity, attr)
class PreDeleteEntityHook(BFSSHook):
""""""
__regid__ = 'bfss_delete_entity'
events = ('before_delete_entity', )
#__select__ = Hook.__select__ & implements('Repository')
def __call__(self):
for attr in ETYPE_ATTR_STORAGE.get(self.entity.__regid__, ()):
ETYPE_ATTR_STORAGE[self.entity.__regid__][attr].entity_deleted(self.entity, attr)