I have the following Table model representing a timeline.
class TimeRange(Base):
__tablename__ = "time_line"
record_id = Column(Integer, primary_key=True)
level = Column(String, nullable=False) # e.g. "Point", "Range"
content = Column(String, nullable=False)
language_marker = Column(String) # this one column is optional and
needs to be queried
immediate_parent_id = Column(Integer, ForeignKey('time_line.record_id'))
child_timelines = relationship('TimeRange', backref=backref(
'parent_timeline', remote_side=[record_id]))
The language_marker Column is the one that needs to be queried in a
recursive manner. Not all records have such an attribute, and the business
logic is: along the hierarchy lineage from the root down to the child
timelines, at least one level of the TimeRange instance carries such an
attribute, and the one in the lowest level should be returned. This works a
little like cascading style sheet, where if the TimeRange object itself
doesn't have such an attribute, just look further up one level above, util
found one, and the latest defined style wins.
What is the technical direction I should look into to implement such
queries? I'm using SQLAlchemy and the backend is SQLite. Thanks.
--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
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