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