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https://github.com/sqlalchemy/sqlalchemy.git
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Mike Bayer
42 lines
1.6 KiB
Python
42 lines
1.6 KiB
Python
"""
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Illustrates three strategies for persisting and querying XML
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documents as represented by ElementTree in a relational
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database. The techniques do not apply any mappings to the
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ElementTree objects directly, so are compatible with the
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native cElementTree as well as lxml, and can be adapted to
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suit any kind of DOM representation system. Querying along
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xpath-like strings is illustrated as well.
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In order of complexity:
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* ``pickle.py`` - Quick and dirty, serialize the whole DOM into a BLOB
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column. While the example is very brief, it has very limited
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functionality.
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* ``adjacency_list.py`` - Each DOM node is stored in an individual
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table row, with attributes represented in a separate table. The
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nodes are associated in a hierarchy using an adjacency list
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structure. A query function is introduced which can search for nodes
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along any path with a given structure of attributes, basically a
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(very narrow) subset of xpath.
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* ``optimized_al.py`` - Uses the same strategy as
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``adjacency_list.py``, but associates each DOM row with its owning
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document row, so that a full document of DOM nodes can be loaded
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using O(1) queries - the construction of the "hierarchy" is performed
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after the load in a non-recursive fashion and is much more
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efficient.
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E.g.::
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# parse an XML file and persist in the database
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doc = ElementTree.parse("test.xml")
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session.add(Document(file, doc))
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session.commit()
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# locate documents with a certain path/attribute structure
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for document in find_document('/somefile/header/field2[@attr=foo]'):
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# dump the XML
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print document
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""" |