BinaryOperation¶
- class lsst.daf.relation.BinaryOperation¶
Bases:
ABC
An abstract base class for operations that act on a pair of relations.
See also
Notes
A
BinaryOperation
represents the operation itself; the combination of an operation and the “lhs” and “rhs” relations it acts on to form a new relation is represented by theBinaryOperationRelation
class, which should always be performed via a call to theapply
method (or something that calls it, like the convenience methods on theRelation
class). In many cases, applying aBinaryOperation
doesn’t return something involving the original operation, because of some combination of defaulted-parameter population and simplification, and there are even someBinaryOperation
classes that should never actually appear in aBinaryOperationRelation
.BinaryOperation
cannot be subclassed by external code.All concrete
BinaryOperation
types are frozen, equality-comparabledataclasses
. They also provide a very concisestr
representation (in addition to the dataclass-providedrepr
) suitable for summarizing an entire relation tree.Methods Summary
applied_columns
(lhs, rhs)Return the columns of the relation that results from applying this operation to the given targets.
applied_max_rows
(lhs, rhs)Return the maximum number of rows of the relation that results from applying this operation to the given target.
applied_min_rows
(lhs, rhs)Return the minimum number of rows of the relation that results from applying this operation to the given targets.
apply
(lhs, rhs)Create a new relation that represents the action of this operation on a pair of existing relations.
Methods Documentation
- abstract applied_columns(lhs: Relation, rhs: Relation) Set[ColumnTag] ¶
Return the columns of the relation that results from applying this operation to the given targets.
- abstract applied_max_rows(lhs: Relation, rhs: Relation) int | None ¶
Return the maximum number of rows of the relation that results from applying this operation to the given target.
- abstract applied_min_rows(lhs: Relation, rhs: Relation) int ¶
Return the minimum number of rows of the relation that results from applying this operation to the given targets.
- final apply(lhs: Relation, rhs: Relation) Relation ¶
Create a new relation that represents the action of this operation on a pair of existing relations.
- Parameters:
- Returns:
- new_relation
Relation
Relation that includes this operation. This may be
self
if the operation is a no-op, and it may not be aBinaryOperationRelation
holding this operation (or even a similar one) if the operation was inserted earlier in the tree via commutation relations.
- new_relation
- Raises:
- ColumnError
Raised if the operation could not be applied due to problems with the target relations’ columns.
- EngineError
Raised if the operation could not be applied due to problems with the target relations’ engine(s).