Coverage for python/lsst/daf/butler/dimensions/record_cache.py: 36%
34 statements
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« prev ^ index » next coverage.py v7.4.3, created at 2024-03-12 10:07 +0000
1# This file is part of daf_butler.
2#
3# Developed for the LSST Data Management System.
4# This product includes software developed by the LSST Project
5# (http://www.lsst.org).
6# See the COPYRIGHT file at the top-level directory of this distribution
7# for details of code ownership.
8#
9# This software is dual licensed under the GNU General Public License and also
10# under a 3-clause BSD license. Recipients may choose which of these licenses
11# to use; please see the files gpl-3.0.txt and/or bsd_license.txt,
12# respectively. If you choose the GPL option then the following text applies
13# (but note that there is still no warranty even if you opt for BSD instead):
14#
15# This program is free software: you can redistribute it and/or modify
16# it under the terms of the GNU General Public License as published by
17# the Free Software Foundation, either version 3 of the License, or
18# (at your option) any later version.
19#
20# This program is distributed in the hope that it will be useful,
21# but WITHOUT ANY WARRANTY; without even the implied warranty of
22# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
23# GNU General Public License for more details.
24#
25# You should have received a copy of the GNU General Public License
26# along with this program. If not, see <http://www.gnu.org/licenses/>.
28from __future__ import annotations
30__all__ = ("DimensionRecordCache",)
32import copy
33from collections.abc import Callable, Iterator, Mapping
35from ._record_set import DimensionRecordSet
36from ._universe import DimensionUniverse
39class DimensionRecordCache(Mapping[str, DimensionRecordSet]):
40 """A mapping of cached dimension records.
42 This object holds all records for elements where
43 `DimensionElement.is_cached` is `True`.
45 Parameters
46 ----------
47 universe : `DimensionUniverse`
48 Definitions of all dimensions.
49 fetch : `~collections.abc.Callable`
50 A callable that takes no arguments and returns a `dict` mapping `str`
51 element name to a `DimensionRecordSet` of all records for that element.
52 They keys of the returned `dict` must be exactly the elements in
53 ``universe`` for which `DimensionElement.is_cached` is `True`.
55 Notes
56 -----
57 The nested `DimensionRecordSet` objects should never be modified in place
58 except when returned by the `modifying` context manager.
59 """
61 def __init__(self, universe: DimensionUniverse, fetch: Callable[[], dict[str, DimensionRecordSet]]):
62 self._universe = universe
63 self._keys = [element.name for element in universe.elements if element.is_cached]
64 self._records: dict[str, DimensionRecordSet] | None = None
65 self._fetch = fetch
67 def reset(self) -> None:
68 """Reset the cache, causing it to be fetched again on next use."""
69 self._records = None
71 def load_from(self, other: DimensionRecordCache) -> None:
72 """Load records from another cache, but do nothing if it doesn't
73 currently have any records.
75 Parameters
76 ----------
77 other : `DimensionRecordCache`
78 Other cache to potentially copy records from.
79 """
80 self._records = copy.deepcopy(other._records)
82 def preload_cache(self) -> None:
83 """Fetch the cache from the DB if it has not already been fetched."""
84 if self._records is None:
85 self._records = self._fetch()
86 assert self._records.keys() == set(self._keys), "Logic bug in fetch callback."
88 def __contains__(self, key: object) -> bool:
89 if not isinstance(key, str):
90 return False
91 if (element := self._universe.get(key)) is not None:
92 return element.is_cached
93 return False
95 def __getitem__(self, element: str) -> DimensionRecordSet:
96 self.preload_cache()
97 assert self._records is not None
98 return self._records[element]
100 def __iter__(self) -> Iterator[str]:
101 return iter(self._keys)
103 def __len__(self) -> int:
104 return len(self._keys)