Coverage for python/lsst/daf/butler/queries/tree/_base.py: 91%

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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 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/>. 

27 

28from __future__ import annotations 

29 

30__all__ = ( 

31 "QueryTreeBase", 

32 "ColumnExpressionBase", 

33 "DatasetFieldName", 

34 "DATASET_FIELD_NAMES", 

35) 

36 

37from abc import ABC, abstractmethod 

38from typing import TYPE_CHECKING, Any, ClassVar, Literal, TypeAlias, TypeVar, cast, get_args 

39 

40import pydantic 

41 

42from ...column_spec import ColumnType 

43 

44if TYPE_CHECKING: 

45 from ..visitors import ColumnExpressionVisitor 

46 from ._column_literal import ColumnLiteral 

47 from ._column_set import ColumnSet 

48 

49 

50# Type annotation for string literals that can be used as dataset fields in 

51# the public API. The 'collection' and 'run' fields are string collection 

52# names. Internal interfaces may define other dataset field strings (e.g. 

53# collection primary key values) and hence should use `str` rather than this 

54# type. 

55DatasetFieldName: TypeAlias = Literal["dataset_id", "ingest_date", "run", "collection", "timespan"] 

56 

57# Tuple of the strings that can be use as dataset fields in public APIs. 

58DATASET_FIELD_NAMES: tuple[DatasetFieldName, ...] = tuple(get_args(DatasetFieldName)) 

59 

60_T = TypeVar("_T") 

61_L = TypeVar("_L") 

62_A = TypeVar("_A") 

63_O = TypeVar("_O") 

64 

65 

66class QueryTreeBase(pydantic.BaseModel): 

67 """Base class for all non-primitive types in a query tree.""" 

68 

69 model_config = pydantic.ConfigDict(frozen=True, extra="forbid", strict=True) 

70 

71 

72class ColumnExpressionBase(QueryTreeBase, ABC): 

73 """Base class for objects that represent non-boolean column expressions in 

74 a query tree. 

75 

76 Notes 

77 ----- 

78 This is a closed hierarchy whose concrete, `~typing.final` derived classes 

79 are members of the `ColumnExpression` union. That union should be used in 

80 type annotations rather than the technically-open base class. 

81 """ 

82 

83 expression_type: str 

84 """String literal corresponding to a concrete expression type.""" 

85 

86 is_literal: ClassVar[bool] = False 

87 """Whether this expression wraps a literal Python value.""" 

88 

89 is_column_reference: ClassVar[bool] = False 

90 """Whether this expression wraps a direct reference to column.""" 

91 

92 @property 

93 @abstractmethod 

94 def column_type(self) -> ColumnType: 

95 """A string enumeration value representing the type of the column 

96 expression. 

97 """ 

98 raise NotImplementedError() 

99 

100 def get_literal_value(self) -> Any | None: 

101 """Return the literal value wrapped by this expression, or `None` if 

102 it is not a literal. 

103 """ 

104 return None 

105 

106 @abstractmethod 

107 def gather_required_columns(self, columns: ColumnSet) -> None: 

108 """Add any columns required to evaluate this expression to the 

109 given column set. 

110 

111 Parameters 

112 ---------- 

113 columns : `ColumnSet` 

114 Set of columns to modify in place. 

115 """ 

116 raise NotImplementedError() 

117 

118 @abstractmethod 

119 def visit(self, visitor: ColumnExpressionVisitor[_T]) -> _T: 

120 """Invoke the visitor interface. 

121 

122 Parameters 

123 ---------- 

124 visitor : `ColumnExpressionVisitor` 

125 Visitor to invoke a method on. 

126 

127 Returns 

128 ------- 

129 result : `object` 

130 Forwarded result from the visitor. 

131 """ 

132 raise NotImplementedError() 

133 

134 

135class ColumnLiteralBase(ColumnExpressionBase): 

136 """Base class for objects that represent literal values as column 

137 expressions in a query tree. 

138 

139 Notes 

140 ----- 

141 This is a closed hierarchy whose concrete, `~typing.final` derived classes 

142 are members of the `ColumnLiteral` union. That union should be used in 

143 type annotations rather than the technically-open base class. The concrete 

144 members of that union are only semi-public; they appear in the serialized 

145 form of a column expression tree, but should only be constructed via the 

146 `make_column_literal` factory function. All concrete members of the union 

147 are also guaranteed to have a read-only ``value`` attribute holding the 

148 wrapped literal, but it is unspecified whether that is a regular attribute 

149 or a `property` (and hence cannot be type-annotated). 

150 """ 

151 

152 is_literal: ClassVar[bool] = True 

153 """Whether this expression wraps a literal Python value.""" 

154 

155 def get_literal_value(self) -> Any: 

156 # Docstring inherited. 

157 return cast("ColumnLiteral", self).value 

158 

159 def gather_required_columns(self, columns: ColumnSet) -> None: 

160 # Docstring inherited. 

161 pass 

162 

163 @property 

164 def column_type(self) -> ColumnType: 

165 # Docstring inherited. 

166 return cast(ColumnType, self.expression_type) 

167 

168 def visit(self, visitor: ColumnExpressionVisitor[_T]) -> _T: 

169 # Docstring inherited 

170 return visitor.visit_literal(cast("ColumnLiteral", self))