mirror of
https://github.com/sqlalchemy/sqlalchemy.git
synced 2026-05-09 10:20:00 -04:00
Mike Bayer
62 lines
1.8 KiB
Python
62 lines
1.8 KiB
Python
"""illustrates a quick and dirty way to persist an XML document expressed using ElementTree and pickle.
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This is a trivial example using PickleType to marshal/unmarshal the ElementTree
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document into a binary column. Compare to explicit.py which stores the individual components of the ElementTree
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structure in distinct rows using two additional mapped entities. Note that the usage of both
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styles of persistence are identical, as is the structure of the main Document class.
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"""
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from sqlalchemy import (create_engine, MetaData, Table, Column, Integer, String,
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PickleType)
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from sqlalchemy.orm import mapper, Session
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import sys, os
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from xml.etree import ElementTree
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e = create_engine('sqlite://')
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meta = MetaData()
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# setup a comparator for the PickleType since it's a mutable
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# element.
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def are_elements_equal(x, y):
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return x == y
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# stores a top level record of an XML document.
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# the "element" column will store the ElementTree document as a BLOB.
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documents = Table('documents', meta,
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Column('document_id', Integer, primary_key=True),
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Column('filename', String(30), unique=True),
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Column('element', PickleType(comparator=are_elements_equal))
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)
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meta.create_all(e)
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# our document class. contains a string name,
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# and the ElementTree root element.
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class Document(object):
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def __init__(self, name, element):
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self.filename = name
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self.element = element
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# setup mapper.
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mapper(Document, documents)
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###### time to test ! #########
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# get ElementTree document
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filename = os.path.join(os.path.dirname(__file__), "test.xml")
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doc = ElementTree.parse(filename)
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# save to DB
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session = Session(e)
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session.add(Document("test.xml", doc))
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session.commit()
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# restore
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document = session.query(Document).filter_by(filename="test.xml").first()
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# print
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document.element.write(sys.stdout)
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