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 "InvalidQueryError", 

35 "DATASET_FIELD_NAMES", 

36) 

37 

38from abc import ABC, abstractmethod 

39from typing import TYPE_CHECKING, Any, ClassVar, Literal, TypeAlias, TypeVar, cast, get_args 

40 

41import pydantic 

42 

43from ...column_spec import ColumnType 

44 

45if TYPE_CHECKING: 

46 from ..visitors import ColumnExpressionVisitor 

47 from ._column_literal import ColumnLiteral 

48 from ._column_set import ColumnSet 

49 

50 

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

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

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

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

55# type. 

56DatasetFieldName: TypeAlias = Literal["dataset_id", "ingest_date", "run", "collection", "timespan"] 

57 

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

59DATASET_FIELD_NAMES: tuple[DatasetFieldName, ...] = tuple(get_args(DatasetFieldName)) 

60 

61_T = TypeVar("_T") 

62_L = TypeVar("_L") 

63_A = TypeVar("_A") 

64_O = TypeVar("_O") 

65 

66 

67class InvalidQueryError(RuntimeError): 

68 """Exception raised when a query is not valid.""" 

69 

70 

71class QueryTreeBase(pydantic.BaseModel): 

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

73 

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

75 

76 

77class ColumnExpressionBase(QueryTreeBase, ABC): 

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

79 a query tree. 

80 

81 Notes 

82 ----- 

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

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

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

86 """ 

87 

88 expression_type: str 

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

90 

91 is_literal: ClassVar[bool] = False 

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

93 

94 @property 

95 @abstractmethod 

96 def precedence(self) -> int: 

97 """Operator precedence for this operation. 

98 

99 Lower values bind more tightly, so parentheses are needed when printing 

100 an expression where an operand has a higher value than the expression 

101 itself. 

102 """ 

103 raise NotImplementedError() 

104 

105 @property 

106 @abstractmethod 

107 def column_type(self) -> ColumnType: 

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

109 expression. 

110 """ 

111 raise NotImplementedError() 

112 

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

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

115 it is not a literal. 

116 """ 

117 return None 

118 

119 @abstractmethod 

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

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

122 given column set. 

123 

124 Parameters 

125 ---------- 

126 columns : `ColumnSet` 

127 Set of columns to modify in place. 

128 """ 

129 raise NotImplementedError() 

130 

131 @abstractmethod 

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

133 """Invoke the visitor interface. 

134 

135 Parameters 

136 ---------- 

137 visitor : `ColumnExpressionVisitor` 

138 Visitor to invoke a method on. 

139 

140 Returns 

141 ------- 

142 result : `object` 

143 Forwarded result from the visitor. 

144 """ 

145 raise NotImplementedError() 

146 

147 

148class ColumnLiteralBase(ColumnExpressionBase): 

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

150 expressions in a query tree. 

151 

152 Notes 

153 ----- 

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

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

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

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

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

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

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

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

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

163 """ 

164 

165 is_literal: ClassVar[bool] = True 

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

167 

168 @property 

169 def precedence(self) -> int: 

170 # Docstring inherited. 

171 return 0 

172 

173 def get_literal_value(self) -> Any: 

174 # Docstring inherited. 

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

176 

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

178 # Docstring inherited. 

179 pass 

180 

181 @property 

182 def column_type(self) -> ColumnType: 

183 # Docstring inherited. 

184 return cast(ColumnType, self.expression_type) 

185 

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

187 # Docstring inherited 

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