Coverage for python/lsst/daf/butler/queries/tree/_base.py: 84%

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 "ANY_DATASET", 

32 "DATASET_FIELD_NAMES", 

33 "AnyDatasetType", 

34 "ColumnExpressionBase", 

35 "DatasetFieldName", 

36 "QueryTreeBase", 

37 "is_dataset_field", 

38) 

39 

40import enum 

41from abc import ABC, abstractmethod 

42from typing import TYPE_CHECKING, Any, ClassVar, Literal, TypeAlias, TypeGuard, TypeVar, cast, get_args 

43 

44import pydantic 

45 

46from ...column_spec import ColumnType 

47 

48if TYPE_CHECKING: 

49 from ..visitors import ColumnExpressionVisitor 

50 from ._column_literal import ColumnLiteral 

51 from ._column_set import ColumnSet 

52 

53 

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

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

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

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

58# type. 

59DatasetFieldName: TypeAlias = Literal["dataset_id", "ingest_date", "run", "collection", "timespan"] 

60 

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

62DATASET_FIELD_NAMES: tuple[DatasetFieldName, ...] = tuple(get_args(DatasetFieldName)) 

63 

64_T = TypeVar("_T") 

65_L = TypeVar("_L") 

66_A = TypeVar("_A") 

67_O = TypeVar("_O") 

68 

69 

70class AnyDatasetType(enum.Enum): 

71 """A single-element enum that provides a typed sentinal dataset type name 

72 for queries over multiple dataset types. 

73 """ 

74 

75 # Since we often use a type-union of ANY_DATASET and str, it's critical 

76 # the enum value (which is what Pydantic uses for serialization) not be 

77 # a str. 

78 ANY_DATASET = -1 

79 

80 def __str__(self) -> str: 

81 # This string appears in both human-read error messages and the aliases 

82 # used for columns in SQL (with quotes, of course). This is a 

83 # convenient value because it sorts before and cannot clash with any 

84 # regular alphabetical name, while still being human readable. 

85 return "[any]" 

86 

87 def __repr__(self) -> str: 

88 return "ANY_DATASET" 

89 

90 

91ANY_DATASET: AnyDatasetType = AnyDatasetType.ANY_DATASET 

92 

93 

94def is_dataset_field(s: str) -> TypeGuard[DatasetFieldName]: 

95 """Validate a field name. 

96 

97 Parameters 

98 ---------- 

99 s : `str` 

100 The field name to test. 

101 

102 Returns 

103 ------- 

104 is_field : `bool` 

105 Whether or not this is a dataset field. 

106 """ 

107 return s in DATASET_FIELD_NAMES 

108 

109 

110class QueryTreeBase(pydantic.BaseModel): 

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

112 

113 model_config = pydantic.ConfigDict(frozen=True, strict=True) 

114 

115 

116class ColumnExpressionBase(QueryTreeBase, ABC): 

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

118 a query tree. 

119 

120 Notes 

121 ----- 

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

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

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

125 """ 

126 

127 expression_type: str 

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

129 

130 is_literal: ClassVar[bool] = False 

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

132 

133 is_column_reference: ClassVar[bool] = False 

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

135 

136 @property 

137 @abstractmethod 

138 def column_type(self) -> ColumnType: 

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

140 expression. 

141 """ 

142 raise NotImplementedError() 

143 

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

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

146 it is not a literal. 

147 """ 

148 return None 

149 

150 @abstractmethod 

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

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

153 given column set. 

154 

155 Parameters 

156 ---------- 

157 columns : `ColumnSet` 

158 Set of columns to modify in place. 

159 """ 

160 raise NotImplementedError() 

161 

162 @abstractmethod 

163 def gather_governors(self, governors: set[str]) -> None: 

164 """Add any governor dimensions that need to be fully identified for 

165 this column expression to be sound. 

166 

167 Parameters 

168 ---------- 

169 governors : `set` [ `str` ] 

170 Set of governor dimension names to modify in place. 

171 """ 

172 raise NotImplementedError() 

173 

174 @abstractmethod 

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

176 """Invoke the visitor interface. 

177 

178 Parameters 

179 ---------- 

180 visitor : `ColumnExpressionVisitor` 

181 Visitor to invoke a method on. 

182 

183 Returns 

184 ------- 

185 result : `object` 

186 Forwarded result from the visitor. 

187 """ 

188 raise NotImplementedError() 

189 

190 

191class ColumnLiteralBase(ColumnExpressionBase): 

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

193 expressions in a query tree. 

194 

195 Notes 

196 ----- 

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

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

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

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

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

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

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

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

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

206 """ 

207 

208 is_literal: ClassVar[bool] = True 

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

210 

211 def get_literal_value(self) -> Any: 

212 # Docstring inherited. 

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

214 

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

216 # Docstring inherited. 

217 pass 

218 

219 def gather_governors(self, governors: set[str]) -> None: 

220 # Docstring inherited. 

221 pass 

222 

223 @property 

224 def column_type(self) -> ColumnType: 

225 # Docstring inherited. 

226 return cast(ColumnType, self.expression_type) 

227 

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

229 # Docstring inherited 

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