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"""
Illustrates "vertical table" mappings.
A "vertical table" refers to a technique where individual attributes
of an object are stored as distinct rows in a table. The "vertical
table" technique is used to persist objects which can have a varied
set of attributes, at the expense of simple query control and brevity.
It is commonly found in content/document management systems in order
to represent user-created structures flexibly.
Two variants on the approach are given. In the second, each row
references a "datatype" which contains information about the type of
information stored in the attribute, such as integer, string, or date.
Example::
shrew = Animal(u'shrew')
shrew[u'cuteness'] = 5
shrew[u'weasel-like'] = False
shrew[u'poisonous'] = True
session.add(shrew)
session.flush()
q = (session.query(Animal).
filter(Animal.facts.any(
and_(AnimalFact.key == u'weasel-like',
AnimalFact.value == True))))
print 'weasel-like animals', q.all()
.. autosource::
"""
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