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""" |
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ETLT |
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Copyright 2016 Set Based IT Consultancy |
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Licence MIT |
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""" |
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import abc |
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import datetime |
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class Type2ReferenceDimension(metaclass=abc.ABCMeta): |
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""" |
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Abstract class for type2 dimensions for which the reference data is supplied with date intervals. |
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""" |
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# ------------------------------------------------------------------------------------------------------------------ |
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def __init__(self): |
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""" |
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Object constructor. |
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""" |
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self._key_key = '' |
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""" |
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The key in the dict returned by call_stored_procedure holding the technical ID. |
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:type: str |
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""" |
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self._key_date_start = '' |
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""" |
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The key in the dict returned by call_stored_procedure holding the start date. |
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:type: str |
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""" |
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self._key_date_end = '' |
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""" |
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The key in the dict returned by call_stored_procedure holding the end date. |
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:type: str |
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""" |
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self._map = {} |
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""" |
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The map from natural keys to lists of tuples with start date, end date, and technical keys. The dates must be in |
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ISO 8601 (YYYY-MM-DD) format. |
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:type: dict[T, list[(str,str,int|None)]] |
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""" |
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# Pre-load look up data in to the map. |
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self.pre_load_data() |
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# ------------------------------------------------------------------------------------------------------------------ |
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def get_id(self, natural_key, date, enhancement=None): |
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""" |
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Returns the technical ID for a natural key at a date or None if the given natural key is not valid. |
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:param T natural_key: The natural key. |
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:param str date: The date in ISO 8601 (YYYY-MM-DD) format. |
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:param T enhancement: Enhancement data of the dimension row. |
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:rtype: int|None |
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""" |
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if not date: |
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return None |
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# If the natural key is known return the technical ID immediately. |
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if natural_key in self._map: |
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for row in self._map[natural_key]: |
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if row[0] <= date <= row[1]: |
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return row[2] |
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# The natural key is not in the map of this dimension. Call a stored procedure for translating the natural key |
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# to a technical key. |
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self.pre_call_stored_procedure() |
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success = False |
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try: |
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row = self.call_stored_procedure(natural_key, date, enhancement) |
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# Convert dates to strings in ISO 8601 format. |
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if isinstance(row[self._key_date_start], datetime.date): |
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row[self._key_date_start] = row[self._key_date_start].isoformat() |
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if isinstance(row[self._key_date_end], datetime.date): |
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row[self._key_date_end] = row[self._key_date_end].isoformat() |
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success = True |
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finally: |
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self.post_call_stored_procedure(success) |
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# Make sure the natural key is in the map. |
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if natural_key not in self._map: |
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self._map[natural_key] = [] |
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if row[self._key_key]: |
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self._map[natural_key].append((row[self._key_date_start], |
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row[self._key_date_end], |
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row[self._key_key])) |
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else: |
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self._map[natural_key].append((date, date, None)) |
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return row[self._key_key] |
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# ------------------------------------------------------------------------------------------------------------------ |
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@abc.abstractmethod |
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def call_stored_procedure(self, natural_key, date, enhancement): |
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""" |
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Call a stored procedure for getting the technical key of a natural key at a date. Returns the technical ID or |
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None if the given natural key is not valid. |
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:param T natural_key: The natural key. |
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:param str date: The date in ISO 8601 (YYYY-MM-DD) format. |
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:param T enhancement: Enhancement data of the dimension row. |
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:rtype: dict |
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""" |
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raise NotImplementedError() |
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# ------------------------------------------------------------------------------------------------------------------ |
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def pre_load_data(self): |
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""" |
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Can be overridden to pre-load lookup data from a dimension table. |
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:rtype: None |
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""" |
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pass |
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# ------------------------------------------------------------------------------------------------------------------ |
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def pre_call_stored_procedure(self): |
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""" |
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This method is invoked before call the stored procedure for getting the technical key of a natural key. |
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In a concurrent environment override this method to acquire a lock on the dimension or dimension hierarchy. |
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:rtype: None |
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""" |
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pass |
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# ------------------------------------------------------------------------------------------------------------------ |
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def post_call_stored_procedure(self, success): |
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""" |
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This method is invoked after calling the stored procedure for getting the technical key of a natural key. |
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In a concurrent environment override this method to release a lock on the dimension or dimension hierarchy and |
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to commit or rollback the transaction. |
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:param bool success: If True the stored procedure is executed successfully. If an exception has occurred. |
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:rtype: None |
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""" |
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pass |
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# ---------------------------------------------------------------------------------------------------------------------- |
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PyETLT /
etlt
