1
|
|
|
""" |
2
|
|
|
ETLT |
3
|
|
|
|
4
|
|
|
Copyright 2016 Set Based IT Consultancy |
5
|
|
|
|
6
|
|
|
Licence MIT |
7
|
|
|
""" |
8
|
|
|
import abc |
9
|
|
|
|
10
|
|
|
|
11
|
|
|
class RegularDimension(metaclass=abc.ABCMeta): |
|
|
|
|
12
|
|
|
""" |
13
|
|
|
Abstract parent class for translating natural key to a technical key of a regular dimension. |
14
|
|
|
""" |
15
|
|
|
|
16
|
|
|
# ------------------------------------------------------------------------------------------------------------------ |
17
|
|
|
def __init__(self): |
18
|
|
|
""" |
19
|
|
|
Object constructor. |
20
|
|
|
""" |
21
|
|
|
|
22
|
|
|
self._map = {} |
23
|
|
|
""" |
24
|
|
|
The map from natural keys to a technical keys. |
25
|
|
|
|
26
|
|
|
:type: dict[T, int|None] |
27
|
|
|
""" |
28
|
|
|
|
29
|
|
|
# Pre-load look up data in to the map. |
30
|
|
|
self.pre_load_data() |
31
|
|
|
|
32
|
|
|
# ------------------------------------------------------------------------------------------------------------------ |
33
|
|
|
def get_id(self, natural_key, enhancement=None): |
34
|
|
|
""" |
35
|
|
|
Returns the technical ID for a natural key or None if the given natural key is not valid. |
36
|
|
|
|
37
|
|
|
:param T natural_key: The natural key. |
38
|
|
|
:param T enhancement: Enhancement data of the dimension row. |
39
|
|
|
|
40
|
|
|
:rtype: int|None |
41
|
|
|
""" |
42
|
|
|
# If the natural key is known return the technical ID immediately. |
43
|
|
|
if natural_key in self._map: |
44
|
|
|
return self._map[natural_key] |
45
|
|
|
|
46
|
|
|
# The natural key is not in the map of this dimension. Call a stored procedure for translating the natural key |
47
|
|
|
# to a technical key. |
48
|
|
|
self.pre_call_stored_procedure() |
49
|
|
|
success = False |
50
|
|
|
try: |
51
|
|
|
key = self.call_stored_procedure(natural_key, enhancement) |
52
|
|
|
success = True |
53
|
|
|
finally: |
54
|
|
|
self.post_call_stored_procedure(success) |
55
|
|
|
|
56
|
|
|
# Add the translation for natural key to technical ID to the map. |
57
|
|
|
self._map[natural_key] = key |
58
|
|
|
|
59
|
|
|
return key |
60
|
|
|
|
61
|
|
|
# ------------------------------------------------------------------------------------------------------------------ |
62
|
|
|
@abc.abstractmethod |
63
|
|
|
def call_stored_procedure(self, natural_key, enhancement): |
64
|
|
|
""" |
65
|
|
|
Calls a stored procedure for getting the technical key of a natural key. Returns the technical ID or None if |
66
|
|
|
the given natural key is not valid. |
67
|
|
|
|
68
|
|
|
:param T natural_key: The natural key. |
69
|
|
|
:param T enhancement: Enhancement data of the dimension row. |
70
|
|
|
|
71
|
|
|
:rtype: int|None |
72
|
|
|
""" |
73
|
|
|
raise NotImplementedError() |
74
|
|
|
|
75
|
|
|
# ------------------------------------------------------------------------------------------------------------------ |
76
|
|
|
def pre_load_data(self): |
77
|
|
|
""" |
78
|
|
|
Can be overridden to pre-load lookup data from a dimension table. |
79
|
|
|
|
80
|
|
|
:rtype: None |
81
|
|
|
""" |
82
|
|
|
pass |
83
|
|
|
|
84
|
|
|
# ------------------------------------------------------------------------------------------------------------------ |
85
|
|
|
def pre_call_stored_procedure(self): |
86
|
|
|
""" |
87
|
|
|
This method is invoked before call the stored procedure for getting the technical key of a natural key. |
88
|
|
|
|
89
|
|
|
In a concurrent environment override this method to acquire a lock on the dimension or dimension hierarchy. |
90
|
|
|
|
91
|
|
|
:rtype: None |
92
|
|
|
""" |
93
|
|
|
pass |
94
|
|
|
|
95
|
|
|
# ------------------------------------------------------------------------------------------------------------------ |
96
|
|
|
def post_call_stored_procedure(self, success): |
97
|
|
|
""" |
98
|
|
|
This method is invoked after calling the stored procedure for getting the technical key of a natural key. |
99
|
|
|
|
100
|
|
|
In a concurrent environment override this method to release a lock on the dimension or dimension hierarchy and |
101
|
|
|
to commit or rollback the transaction. |
102
|
|
|
|
103
|
|
|
:param bool success: If True the stored procedure is executed successfully. If an exception has occurred. |
104
|
|
|
|
105
|
|
|
:rtype: None |
106
|
|
|
""" |
107
|
|
|
pass |
108
|
|
|
|
109
|
|
|
# ---------------------------------------------------------------------------------------------------------------------- |
110
|
|
|
|