Re: [sqlalchemy] dirtying attributes of a user-defined type
On Jan 13, 2011, at 3:29 PM, Michael Bayer wrote:
There's mistakes in how this is structured. UserDefinedType represents a
type object applied to a Column. The actual data handled by such a type is
not meant to be an instance of the type itself. ACLItem() here would be its
own class, and UserDefinedType would be the superclass of a class like
ACLItemType.ACLItemType() is placed on the Column, and its
bind_processor() and result_processor() deal with ACLItem objects.
Once you have the roles of type and value set up, you'd want to mixin
sqlalchemy.types.MutableType, which alerts the ORM that the value of this
type can change inline. Note that MutableType is not recommended for high
volume applications as it performs terribly, due to the need for flush() to
scan all mutables in the session for changes every time it's called - 0.7
has a new extension that allows mutable values to send change events in an
efficient manner.
Thank you for the detailed response!
I have implemented all of your advice, but have hit another roadblock-
specifically, I cannot determine how to properly cast the array type from
within the ACLItemArrayType class.
../sqlalchemy/engine/default.py, line 299, in do_execute
cursor.execute(statement, parameters)
ProgrammingError: (ProgrammingError) column aclarray is of type aclitem[] but
expression is of type text[]
LINE 1: INSERT INTO imageaclarray (aclarray) VALUES (ARRAY[E'user te...
^
HINT: You will need to rewrite or cast the expression.
'INSERT INTO imageaclarray (aclarray) VALUES (%(aclarray)s) RETURNING
imageaclarray.id' {'aclarray': ['user testrole1=rU*/testrole1', 'user
testrole2=Xc/testrole1']}
What is really need is:
insert into imageaclarray (aclarray) values (ARRAY[E'user
agentm=rU*/agentm',E'user agentm=Xc/agentm']::aclitem[]);
or
insert into imageaclarray (aclarray) values (ARRAY[E'user
agentm=rU*/agentm'::aclitem,E'user agentm=Xc/agentm'::aclitem]);
but I can't figure out how to add casting or if it is even possible... clearly
bind_processor is too late, but psycopg2 doesn't seem to offer an option to set
the oid for the container array either. Is there a method during compilation I
can use?
Cheers,
M
Code and unit test follow:
=
import sqlalchemy.types as types
import re
import sqlalchemy.exc
from sqlalchemy.dialects.postgresql import ARRAY
#include/utils/acl.h
#define ACL_ALL_RIGHTS_STR arwdDxtXUCTc
#update for SQLAlchemy 0.7:
http://www.sqlalchemy.org/docs/07/orm/extensions/mutable.html
class ACLItem(object):
def __init__(self,grantee,permissions,grantor,grant_option=False):
self.grantee = grantee
self.permissions = []
if permissions:
for p in permissions:
self.permissions.append(p)
self.grantor = grantor
self.grant_option = grant_option
def _as_pgsql_string(self):
#convert to string 'user grantee=perms/grantor'
string_perms = ''
for perm in self.permissions:
string_perms += perm
if self.grant_option:
grant_option = '*'
else:
grant_option = ''
return user %s=%s%s/%s %
(self.grantee,string_perms,grant_option,self.grantor)
@classmethod
def _from_pgsql_string(klass,aclstring):
grantee=perms*/grantor
matches = re.match('([^=]+)=([^/\*]+)(\*?)/(\w+)',aclstring)
if matches is None:
raise sqlalchemy.exc.DataError(aclstring,[],'')
grantee = matches.group(1)
permissions = matches.group(2)
grant_option = bool(len(matches.group(3)))
grantor = matches.group(4)
return ACLItem(grantee,permissions,grantor,grant_option)
def __eq__(self,other_object):
if not isinstance(other_object,self.__class__):
return False
return str(self) == str(other_object)
def has_permission(self,permission_test):
return permission_test in self.permissions
def set_permission(self,permission,on=True):
if not self.has_permission(permission) and on:
self.permissions.append(permission)
elif self.has_permission(permission) and not on:
self.permissions.remove(permission)
def clear_permissions(self):
del self.permissions[:]
def reset_with_acl(self,acl):
takes an acl and replaces its own settings with the argument settings
This is useful for cases where an acl in an array is replaced without
being creating a new aclitem so that the array order in unmodified
self.grantee = acl.grantee
self.permissions = acl.permissions
self.grantor = acl.grantor
self.grant_option = acl.grant_option
def __str__(self):
return self._as_pgsql_string()
class ACLItemArray(list):
#in an aclitem array, the
def
Re: [sqlalchemy] dirtying attributes of a user-defined type
On Jan 14, 2011, at 3:26 PM, A.M. wrote:
I suspect I have to implement special converter methods with psycopg2
register_adapter/new_type. That is what I am experimenting with now.
It looks like SQLAlchemy's array type support doesn't support anything beyond
basic built-in types that accept numbers or text values. (Please do correct me
if I am wrong.) I suspect this is a limitation of the default psycopg2 array
support which does not allow passing a type along with the array during
execution. It also seems to always bind arrays inline.
I worked around this by installing type converters directly in psycopg2.
SQLAlchemy then ends up with the values as pre-cooked ACLItem and ACLItemArray
objects. From an external API standpoint, nothing changed.
One stumbling block I had was that the code sample in the docs was too slim and
there is no UserDefinedType example in the examples directory, so I spent a lot
of time in the debugger. I hope this code may help others.
Here is the code that worked:
==
import sqlalchemy.types as types
import re
import sqlalchemy.exc
from sqlalchemy.dialects.postgresql import ARRAY
from project.lib.aclitem import ACLItem,ACLItemArray
from copy import deepcopy
#include/utils/acl.h
#define ACL_ALL_RIGHTS_STR arwdDxtXUCTc
#update for SQLAlchemy 0.7:
http://www.sqlalchemy.org/docs/07/orm/extensions/mutable.html
class
ACLItemArrayType(types.MutableType,types.UserDefinedType,types.Concatenable):
def get_col_spec(self):
return 'aclitem[]'
def bind_processor(self,dialect):
return None
def result_process(self,dialect):
return None
def copy_value(self,value):
return deepcopy(value)
def compare_values(self,a,b):
return a == b
class ACLItemType(types.MutableType,types.UserDefinedType):
#class ACLItemType(types.UserDefinedType,types.MutableType): #FAIL
def get_col_spec(self):
return 'aclitem'
def bind_processor(self,dialect):
return None
def copy_value(self,value):
return deepcopy(value)
def result_processor(self,dialect,column_type):
return None
===
import re
from copy import deepcopy
class ACLItem(object):
def __init__(self,grantee,permissions,grantor,grant_option=False):
self.grantee = grantee
self.permissions = []
if permissions:
for p in permissions:
self.permissions.append(p)
self.grantor = grantor
self.grant_option = grant_option
def _as_pgsql_string(self):
#convert to string 'user grantee=perms/grantor'
string_perms = ''
for perm in self.permissions:
string_perms += perm
if self.grant_option:
grant_option = '*'
else:
grant_option = ''
return user %s=%s%s/%s %
(self.grantee,string_perms,grant_option,self.grantor)
def __deepcopy__(self,memo):
return
ACLItem(self.grantee,self.permissions,self.grantor,self.grant_option)
def __copy__(self):
return deepcopy(self)
@classmethod
def _from_pgsql_string(klass,aclstring):
grantee=perms*/grantor
matches = re.match('([^=]+)=([^/\*]+)(\*?)/(\w+)',aclstring)
if matches is None:
raise ValueError('string does not appear to represent a PostgreSQL
ACL')
grantee = matches.group(1)
permissions = matches.group(2)
grant_option = bool(len(matches.group(3)))
grantor = matches.group(4)
return ACLItem(grantee,permissions,grantor,grant_option)
def __eq__(self,other_object):
if not isinstance(other_object,self.__class__):
return False
return str(self) == str(other_object)
def has_permission(self,permission_test):
return permission_test in self.permissions
def set_permission(self,permission,on=True):
if not self.has_permission(permission) and on:
self.permissions.append(permission)
elif self.has_permission(permission) and not on:
self.permissions.remove(permission)
def clear_permissions(self):
del self.permissions[:]
def reset_with_acl(self,acl):
takes an acl and replaces its own settings with the argument settings
This is useful for cases where an acl in an array is replaced without
being creating a new aclitem so that the array order in unmodified
self.grantee = acl.grantee
self.permissions = acl.permissions
self.grantor = acl.grantor
self.grant_option = acl.grant_option
def __str__(self):
return self._as_pgsql_string()
def __repr__(self):
return ACLItem('%s',%s,'%s',%s) %
(self.grantee,self.permissions,self.grantor,self.grant_option)
class ACLItemArray(list):
#in an aclitem array, the
def aclitem_for_grantee(self,role):
for acl in self:
if role ==
[sqlalchemy] dirtying attributes of a user-defined type
Hello,
I have created an SQLAlchemy type which represents a postgresql aclitem (which
represents postgresql access control lists). I am able to load and save
newly-created ACLItems from the database, however, modifying the values of an
instance of the type does not dirty it for flushing. Is there some decorator
for dirtying accessors to the type instance convenience methods?
Specifically, modifying any of grantee, grantor, permissions, and
grant_option, does not trigger a proper update.
Cheers,
M
import sqlalchemy.types as types
import re
import sqlalchemy.exc
#include/utils/acl.h
#define ACL_ALL_RIGHTS_STR arwdDxtXUCTc
class ACLItem(types.UserDefinedType):
def
__init__(self,grantee=None,permissions=None,grantor=None,grant_option=False):
#note that sqlalchemy calls this with None arguments for processing
self.grantee = grantee
self.permissions = []
if permissions:
for p in permissions:
self.permissions.append(p)
self.grantor = grantor
self.grant_option = grant_option
def get_col_spec(self):
return 'aclitem'
def bind_processor(self,dialect):
def acl2string(aclitem):
return aclitem._as_pgsql_string()
return acl2string
def compare_values(self,a,b):
return a._as_pgsql_string() == b._as_pgsql_string()
def _as_pgsql_string(self):
#convert to string 'user grantee=perms/grantor'
string_perms = ''
for perm in self.permissions:
string_perms += perm
if self.grant_option:
grant_option = '*'
else:
grant_option = ''
return user %s=%s%s/%s %
(self.grantee,string_perms,grant_option,self.grantor)
@classmethod
def _from_pgsql_string(klass,aclstring):
grantee=perms*/grantor
matches = re.match('([^=]+)=([^/\*]+)(\*?)/(\w+)',aclstring)
if matches is None:
raise sqlalchemy.exc.DataError(aclstring,[],'')
grantee = matches.group(1)
permissions = matches.group(2)
grant_option = len(matches.group(3))
grantor = matches.group(4)
return ACLItem(grantee,permissions,grantor,grant_option)
def result_processor(self,dialect,column_type):
def string2acl(aclstring):
return ACLItem._from_pgsql_string(aclstring)
return string2acl
def has_permission(self,permission_test):
return permission_test in self.permissions
def set_permission(self,permission,on=True):
if not self.has_permission(permission):
if on:
self.permissions.append(permission)
else:
self.permissions.remove(permission)
def clear_permissions(self):
del self.permissions[:]
def __str__(self):
return self._as_pgsql_string()
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Re: [sqlalchemy] dirtying attributes of a user-defined type
There's mistakes in how this is structured. UserDefinedType represents a type
object applied to a Column. The actual data handled by such a type is not
meant to be an instance of the type itself. ACLItem() here would be its own
class, and UserDefinedType would be the superclass of a class like
ACLItemType.ACLItemType() is placed on the Column, and its
bind_processor() and result_processor() deal with ACLItem objects.
Once you have the roles of type and value set up, you'd want to mixin
sqlalchemy.types.MutableType, which alerts the ORM that the value of this type
can change inline. Note that MutableType is not recommended for high volume
applications as it performs terribly, due to the need for flush() to scan all
mutables in the session for changes every time it's called - 0.7 has a new
extension that allows mutable values to send change events in an efficient
manner.
On Jan 13, 2011, at 1:33 PM, A.M. wrote:
Hello,
I have created an SQLAlchemy type which represents a postgresql aclitem
(which represents postgresql access control lists). I am able to load and
save newly-created ACLItems from the database, however, modifying the values
of an instance of the type does not dirty it for flushing. Is there some
decorator for dirtying accessors to the type instance convenience methods?
Specifically, modifying any of grantee, grantor, permissions, and
grant_option, does not trigger a proper update.
Cheers,
M
import sqlalchemy.types as types
import re
import sqlalchemy.exc
#include/utils/acl.h
#define ACL_ALL_RIGHTS_STR arwdDxtXUCTc
class ACLItem(types.UserDefinedType):
def
__init__(self,grantee=None,permissions=None,grantor=None,grant_option=False):
#note that sqlalchemy calls this with None arguments for processing
self.grantee = grantee
self.permissions = []
if permissions:
for p in permissions:
self.permissions.append(p)
self.grantor = grantor
self.grant_option = grant_option
def get_col_spec(self):
return 'aclitem'
def bind_processor(self,dialect):
def acl2string(aclitem):
return aclitem._as_pgsql_string()
return acl2string
def compare_values(self,a,b):
return a._as_pgsql_string() == b._as_pgsql_string()
def _as_pgsql_string(self):
#convert to string 'user grantee=perms/grantor'
string_perms = ''
for perm in self.permissions:
string_perms += perm
if self.grant_option:
grant_option = '*'
else:
grant_option = ''
return user %s=%s%s/%s %
(self.grantee,string_perms,grant_option,self.grantor)
@classmethod
def _from_pgsql_string(klass,aclstring):
grantee=perms*/grantor
matches = re.match('([^=]+)=([^/\*]+)(\*?)/(\w+)',aclstring)
if matches is None:
raise sqlalchemy.exc.DataError(aclstring,[],'')
grantee = matches.group(1)
permissions = matches.group(2)
grant_option = len(matches.group(3))
grantor = matches.group(4)
return ACLItem(grantee,permissions,grantor,grant_option)
def result_processor(self,dialect,column_type):
def string2acl(aclstring):
return ACLItem._from_pgsql_string(aclstring)
return string2acl
def has_permission(self,permission_test):
return permission_test in self.permissions
def set_permission(self,permission,on=True):
if not self.has_permission(permission):
if on:
self.permissions.append(permission)
else:
self.permissions.remove(permission)
def clear_permissions(self):
del self.permissions[:]
def __str__(self):
return self._as_pgsql_string()
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