Coverage for python/lsst/daf/butler/registry/queries/find_first_dataset.py: 79%

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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 program is free software: you can redistribute it and/or modify 

10# it under the terms of the GNU General Public License as published by 

11# the Free Software Foundation, either version 3 of the License, or 

12# (at your option) any later version. 

13# 

14# This program is distributed in the hope that it will be useful, 

15# but WITHOUT ANY WARRANTY; without even the implied warranty of 

16# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 

17# GNU General Public License for more details. 

18# 

19# You should have received a copy of the GNU General Public License 

20# along with this program. If not, see <http://www.gnu.org/licenses/>. 

21from __future__ import annotations 

22 

23__all__ = ("FindFirstDataset",) 

24 

25import dataclasses 

26from collections.abc import Sequence, Set 

27from typing import final 

28 

29from lsst.daf.relation import ColumnTag, Relation, RowFilter 

30from lsst.utils.classes import cached_getter 

31 

32from ...core import DatasetColumnTag, DimensionKeyColumnTag 

33 

34 

35@final 

36@dataclasses.dataclass(frozen=True) 

37class FindFirstDataset(RowFilter): 

38 """A custom relation operation that selects the first dataset from an 

39 upstream relation according to its collection rank. 

40 """ 

41 

42 dimensions: Sequence[DimensionKeyColumnTag] 

43 """Dimensions to group by while finding the first dataset within each group 

44 (`~collections.abc.Sequence` [ `DimensionKeyColumnTag` ]). 

45 """ 

46 

47 rank: DatasetColumnTag 

48 """Dataset rank column whose lowest per-group values should be selected 

49 (`DatasetColumnTag`). 

50 """ 

51 

52 @property 

53 @cached_getter 

54 def columns_required(self) -> Set[ColumnTag]: 

55 # Docstring inherited. 

56 result: set[ColumnTag] = {self.rank} 

57 result.update(self.dimensions) 

58 return result 

59 

60 @property 

61 def is_empty_invariant(self) -> bool: 

62 # Docstring inherited. 

63 return True 

64 

65 @property 

66 def is_order_dependent(self) -> bool: 

67 # Docstring inherited. 

68 return False 

69 

70 def __str__(self) -> str: 

71 return "find_first" 

72 

73 def applied_min_rows(self, target: Relation) -> int: 

74 # Docstring inherited. 

75 return 1 if target.min_rows else 0