/usr/lib/python2.7/dist-packages/twext/enterprise/dal/record.py is in calendarserver 5.2+dfsg-1.
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##
# Copyright (c) 2012-2014 Apple Inc. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
##
"""
RECORD: Relational Entity Creation from Objects Representing Data.
This is an asynchronous object-relational mapper based on
L{twext.enterprise.dal.syntax}.
"""
from twisted.internet.defer import inlineCallbacks, returnValue
from twext.enterprise.dal.syntax import (
Select, Tuple, Constant, ColumnSyntax, Insert, Update, Delete
)
from twext.enterprise.util import parseSQLTimestamp
# from twext.enterprise.dal.syntax import ExpressionSyntax
class ReadOnly(AttributeError):
"""
A caller attempted to set an attribute on a database-backed record, rather
than updating it through L{Record.update}.
"""
def __init__(self, className, attributeName):
self.className = className
self.attributeName = attributeName
super(ReadOnly, self).__init__("SQL-backed attribute '{0}.{1}' is "
"read-only. Use '.update(...)' to "
"modify attributes."
.format(className, attributeName))
class NoSuchRecord(Exception):
"""
No matching record could be found.
"""
class _RecordMeta(type):
"""
Metaclass for associating a L{fromTable} with a L{Record} at inheritance
time.
"""
def __new__(cls, name, bases, ns):
"""
Create a new instance of this meta-type.
"""
newbases = []
table = None
namer = None
for base in bases:
if isinstance(base, fromTable):
if table is not None:
raise RuntimeError(
"Can't define a class from two or more tables at once."
)
table = base.table
elif getattr(base, "table", None) is not None:
raise RuntimeError(
"Can't define a record class by inheriting one already "
"mapped to a table."
# TODO: more info
)
else:
if namer is None:
if isinstance(base, _RecordMeta):
namer = base
newbases.append(base)
if table is not None:
attrmap = {}
colmap = {}
allColumns = list(table)
for column in allColumns:
attrname = namer.namingConvention(column.model.name)
attrmap[attrname] = column
colmap[column] = attrname
ns.update(table=table, __attrmap__=attrmap, __colmap__=colmap)
ns.update(attrmap)
return super(_RecordMeta, cls).__new__(cls, name, tuple(newbases), ns)
class fromTable(object):
"""
Inherit from this after L{Record} to specify which table your L{Record}
subclass is mapped to.
"""
def __init__(self, aTable):
"""
@param table: The table to map to.
@type table: L{twext.enterprise.dal.syntax.TableSyntax}
"""
self.table = aTable
class Record(object):
"""
Superclass for all database-backed record classes. (i.e. an object mapped
from a database record).
@cvar table: the table that represents this L{Record} in the database.
@type table: L{TableSyntax}
@ivar transaction: The L{IAsyncTransaction} where this record is being
loaded. This may be C{None} if this L{Record} is not participating in
a transaction, which may be true if it was instantiated but never
saved.
@cvar __colmap__: map of L{ColumnSyntax} objects to attribute names.
@type __colmap__: L{dict}
@cvar __attrmap__: map of attribute names to L{ColumnSyntax} objects.
@type __attrmap__: L{dict}
"""
__metaclass__ = _RecordMeta
transaction = None
def __setattr__(self, name, value):
"""
Once the transaction is initialized, this object is immutable. If you
want to change it, use L{Record.update}.
"""
if self.transaction is not None:
raise ReadOnly(self.__class__.__name__, name)
return super(Record, self).__setattr__(name, value)
def __repr__(self):
r = "<{0} record from table {1}".format(self.__class__.__name__,
self.table.model.name)
for k in sorted(self.__attrmap__.keys()):
r += " {0}={1}".format(k, repr(getattr(self, k)))
r += ">"
return r
@staticmethod
def namingConvention(columnName):
"""
Implement the convention for naming-conversion between column names
(typically, upper-case database names map to lower-case attribute
names).
"""
words = columnName.lower().split("_")
def cap(word):
if word.lower() == 'id':
return word.upper()
else:
return word.capitalize()
return words[0] + "".join(map(cap, words[1:]))
@classmethod
def _primaryKeyExpression(cls):
return Tuple([ColumnSyntax(c) for c in cls.table.model.primaryKey])
def _primaryKeyValue(self):
val = []
for col in self._primaryKeyExpression().columns:
val.append(getattr(self, self.__class__.__colmap__[col]))
return val
@classmethod
def _primaryKeyComparison(cls, primaryKey):
return (cls._primaryKeyExpression() ==
Tuple(map(Constant, primaryKey)))
@classmethod
@inlineCallbacks
def load(cls, transaction, *primaryKey):
results = (yield cls.query(transaction,
cls._primaryKeyComparison(primaryKey)))
if len(results) != 1:
raise NoSuchRecord()
else:
returnValue(results[0])
@classmethod
@inlineCallbacks
def create(cls, transaction, **k):
"""
Create a row.
Used like this::
MyRecord.create(transaction, column1=1, column2=u'two')
"""
self = cls()
colmap = {}
attrtocol = cls.__attrmap__
needsCols = []
needsAttrs = []
for attr in attrtocol:
col = attrtocol[attr]
if attr in k:
setattr(self, attr, k[attr])
colmap[col] = k.pop(attr)
else:
if col.model.needsValue():
raise TypeError("required attribute " + repr(attr) +
" not passed")
else:
needsCols.append(col)
needsAttrs.append(attr)
if k:
raise TypeError("received unknown attribute{0}: {1}".format(
"s" if len(k) > 1 else "", ", ".join(sorted(k))
))
result = yield (Insert(colmap, Return=needsCols if needsCols else None)
.on(transaction))
if needsCols:
self._attributesFromRow(zip(needsAttrs, result[0]))
self.transaction = transaction
returnValue(self)
def _attributesFromRow(self, attributeList):
"""
Take some data loaded from a row and apply it to this instance,
converting types as necessary.
@param attributeList: a C{list} of 2-C{tuples} of C{(attributeName,
attributeValue)}.
"""
for setAttribute, setValue in attributeList:
setColumn = self.__attrmap__[setAttribute]
if setColumn.model.type.name == "timestamp":
setValue = parseSQLTimestamp(setValue)
setattr(self, setAttribute, setValue)
def delete(self):
"""
Delete this row from the database.
@return: a L{Deferred} which fires with C{None} when the underlying row
has been deleted, or fails with L{NoSuchRecord} if the underlying
row was already deleted.
"""
return Delete(From=self.table,
Where=self._primaryKeyComparison(self._primaryKeyValue())
).on(self.transaction, raiseOnZeroRowCount=NoSuchRecord)
@inlineCallbacks
def update(self, **kw):
"""
Modify the given attributes in the database.
@return: a L{Deferred} that fires when the updates have been sent to
the database.
"""
colmap = {}
for k, v in kw.iteritems():
colmap[self.__attrmap__[k]] = v
yield (Update(colmap,
Where=self._primaryKeyComparison(self._primaryKeyValue()))
.on(self.transaction))
self.__dict__.update(kw)
@classmethod
def pop(cls, transaction, *primaryKey):
"""
Atomically retrieve and remove a row from this L{Record}'s table
with a primary key value of C{primaryKey}.
@return: a L{Deferred} that fires with an instance of C{cls}, or fails
with L{NoSuchRecord} if there were no records in the database.
@rtype: L{Deferred}
"""
return cls._rowsFromQuery(
transaction, Delete(Where=cls._primaryKeyComparison(primaryKey),
From=cls.table, Return=list(cls.table)),
lambda : NoSuchRecord()
).addCallback(lambda x: x[0])
@classmethod
def query(cls, transaction, expr, order=None, ascending=True, group=None):
"""
Query the table that corresponds to C{cls}, and return instances of
C{cls} corresponding to the rows that are returned from that table.
@param expr: An L{ExpressionSyntax} that constraints the results of the
query. This is most easily produced by accessing attributes on the
class; for example, C{MyRecordType.query((MyRecordType.col1 >
MyRecordType.col2).And(MyRecordType.col3 == 7))}
@param order: A L{ColumnSyntax} to order the resulting record objects
by.
@param ascending: A boolean; if C{order} is not C{None}, whether to
sort in ascending or descending order.
@param group: a L{ColumnSyntax} to group the resulting record objects
by.
"""
kw = {}
if order is not None:
kw.update(OrderBy=order, Ascending=ascending)
if group is not None:
kw.update(GroupBy=group)
return cls._rowsFromQuery(transaction, Select(list(cls.table),
From=cls.table,
Where=expr, **kw), None)
@classmethod
def all(cls, transaction):
"""
Load all rows from the table that corresponds to C{cls} and return
instances of C{cls} corresponding to all.
"""
return cls._rowsFromQuery(transaction,
Select(list(cls.table),
From=cls.table,
OrderBy=cls._primaryKeyExpression()),
None)
@classmethod
@inlineCallbacks
def _rowsFromQuery(cls, transaction, qry, rozrc):
"""
Execute the given query, and transform its results into instances of
C{cls}.
@param transaction: an L{IAsyncTransaction} to execute the query on.
@param qry: a L{_DMLStatement} (XXX: maybe _DMLStatement or some
interface that defines 'on' should be public?) whose results are
the list of columns in C{self.table}.
@param rozrc: The C{raiseOnZeroRowCount} argument.
@return: a L{Deferred} that succeeds with a C{list} of instances of
C{cls} or fails with an exception produced by C{rozrc}.
"""
rows = yield qry.on(transaction, raiseOnZeroRowCount=rozrc)
selves = []
names = [cls.__colmap__[column] for column in list(cls.table)]
for row in rows:
self = cls()
self._attributesFromRow(zip(names, row))
self.transaction = transaction
selves.append(self)
returnValue(selves)
__all__ = [
"ReadOnly",
"fromTable",
"NoSuchRecord",
]
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