model.py 文件源码

def setup():
    """
    Set up ORM.

    Does not create any database tables, see :py:func:`create_tables`
    for that.
    """
    global resource_metadata_table
    if resource_metadata_table is None:
        log.debug('Defining resource metadata table')
        resource_metadata_table = Table(
            RESOURCE_METADATA_TABLE_NAME,
            metadata,
            Column('resource_id', types.UnicodeText, ForeignKey('resource.id',
                   ondelete='CASCADE', onupdate='CASCADE'), nullable=False,
                   primary_key=True),
            Column('last_extracted', types.DateTime),
            Column('last_url', types.UnicodeText),
            Column('last_format', types.UnicodeText),
            Column('task_id', types.UnicodeText)
        )
        mapper(
            ResourceMetadata,
            resource_metadata_table,
            properties={
                '_meta': relationship(ResourceMetadatum, collection_class=
                                      attribute_mapped_collection('key'),
                                      cascade='all, delete, delete-orphan'),
            }
        )
    else:
        log.debug('Resource metadata table already defined')
    global resource_metadatum_table
    if resource_metadatum_table is None:
        log.debug('Defining resource metadatum table')
        resource_metadatum_table = Table(
            RESOURCE_METADATUM_TABLE_NAME,
            metadata,
            Column('id', types.Integer, nullable=False, primary_key=True),
            Column('resource_id', types.UnicodeText, ForeignKey(
                   RESOURCE_METADATA_TABLE_NAME + '.resource_id',
                   ondelete='CASCADE', onupdate='CASCADE'), nullable=False),
            Column('key', types.UnicodeText, nullable=False),
            Column('value', types.UnicodeText)
        )
        mapper(ResourceMetadatum, resource_metadatum_table)
    else:
        log.debug('Resource metadatum table already defined')