"""illustrates an explicit way to persist an XML document expressed using ElementTree.
-This example explicitly marshals/unmarshals the ElementTree document into
-mapped entities which have their own tables. Compare to pickle.py which
+This example explicitly marshals/unmarshals the ElementTree document into
+mapped entities which have their own tables. Compare to pickle.py which
uses pickle to accomplish the same task. Note that the usage of both
styles of persistence are identical, as is the structure of the main Document class.
"""
-################################# PART I - Imports/Coniguration ###########################################
+################################# PART I - Imports/Coniguration ####################################
from sqlalchemy import (MetaData, Table, Column, Integer, String, ForeignKey,
Unicode, and_)
from sqlalchemy.orm import mapper, relation, create_session, lazyload
meta = MetaData()
meta.bind = 'sqlite://'
-################################# PART II - Table Metadata ###########################################
-
-# stores a top level record of an XML document.
+################################# PART II - Table Metadata #########################################
+
+# stores a top level record of an XML document.
documents = Table('documents', meta,
Column('document_id', Integer, primary_key=True),
Column('filename', String(30), unique=True),
Column('element_id', Integer, ForeignKey('elements.element_id'))
)
-# stores XML nodes in an adjacency list model. This corresponds to
+# stores XML nodes in an adjacency list model. This corresponds to
# Element and SubElement objects.
elements = Table('elements', meta,
Column('element_id', Integer, primary_key=True),
#################################### PART III - Model #############################################
# our document class. contains a string name,
-# and the ElementTree root element.
+# and the ElementTree root element.
class Document(object):
def __init__(self, name, element):
self.filename = name
self.element = element
-
+
def __str__(self):
buf = StringIO.StringIO()
self.element.write(buf)
return buf.getvalue()
-#################################### PART IV - Persistence Mapping ###################################
+#################################### PART IV - Persistence Mapping #################################
-# Node class. a non-public class which will represent
+# Node class. a non-public class which will represent
# the DB-persisted Element/SubElement object. We cannot create mappers for
-# ElementTree elements directly because they are at the very least not new-style
+# ElementTree elements directly because they are at the very least not new-style
# classes, and also may be backed by native implementations.
# so here we construct an adapter.
class _Node(object):
pass
-# Attribute class. also internal, this will represent the key/value attributes stored for
+# Attribute class. also internal, this will represent the key/value attributes stored for
# a particular Node.
class _Attribute(object):
def __init__(self, name, value):
})
mapper(_Node, elements, properties={
- 'children':relation(_Node, cascade="all"),
- 'attributes':relation(_Attribute, lazy=False, cascade="all, delete-orphan"), # eagerly load attributes
+ 'children':relation(_Node, cascade="all"),
+ # eagerly load attributes
+ 'attributes':relation(_Attribute, lazy=False, cascade="all, delete-orphan"),
})
mapper(_Attribute, attributes)
def __get__(self, document, owner):
if document is None:
return self
-
+
if hasattr(document, '_element'):
return document._element
-
+
def traverse(node, parent=None):
if parent is not None:
elem = ElementTree.SubElement(parent, node.tag)
document._element = ElementTree.ElementTree(traverse(document._root))
return document._element
-
+
def __set__(self, document, element):
def traverse(node):
n = _Node()
document._root = traverse(element.getroot())
document._element = element
-
+
def __delete__(self, document):
del document._element
document._root = []
# override Document's "element" attribute with the marshaller.
Document.element = ElementTreeMarshal()
-########################################### PART V - Basic Persistence Example ############################
+########################################### PART V - Basic Persistence Example #####################
line = "\n--------------------------------------------------------"
print document
-############################################ PART VI - Searching for Paths #######################################
+############################################ PART VI - Searching for Paths #########################
# manually search for a document which contains "/somefile/header/field1:hi"
d = session.query(Document).join('_root', aliased=True).filter(_Node.tag==u'somefile').\
join('children', aliased=True, from_joinpoint=True).filter(_Node.tag==u'header').\
- join('children', aliased=True, from_joinpoint=True).filter(and_(_Node.tag==u'field1', _Node.text==u'hi')).\
- one()
+ join('children', aliased=True, from_joinpoint=True).filter(
+ and_(_Node.tag==u'field1', _Node.text==u'hi')).one()
print d
# generalize the above approach into an extremely impoverished xpath function:
attribute = 'children'
if attrname:
if attrvalue:
- query = query.join('attributes', aliased=True, from_joinpoint=True).filter(and_(_Attribute.name==attrname, _Attribute.value==attrvalue))
+ query = query.join('attributes', aliased=True, from_joinpoint=True).filter(
+ and_(_Attribute.name==attrname, _Attribute.value==attrvalue))
else:
- query = query.join('attributes', aliased=True, from_joinpoint=True).filter(_Attribute.name==attrname)
+ query = query.join('attributes', aliased=True, from_joinpoint=True).filter(
+ _Attribute.name==attrname)
return query.options(lazyload('_root')).filter(_Node.text==compareto).all()
for path, compareto in (
projects / thirdparty / sqlalchemy / sqlalchemy.git / commitdiff
