Chain¶

class lsst.daf.relation.Chain¶

Bases: lsst.daf.relation.BinaryOperation

A relation operation that concatenates the rows of a pair of relations with the same columns.

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

applied_columns(lhs: Relation, rhs: Relation) → Set[ColumnTag]¶

Return the columns of the relation that results from applying this operation to the given targets.

Parameters:	lhs : `Relation` On relation the operation will act on. rhs : `Relation` The other relation the operation will act on.
Returns:	columns : `Set` [ `ColumnTag` ] Columns the new relation would have.

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.

Parameters:	lhs : `Relation` On relation the operation will act on. rhs : `Relation` The other relation the operation will act on.
Returns:	max_rows : `int` or `None` Maximum number of rows the new relation would have.

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.

Parameters:	lhs : `Relation` On relation the operation will act on. rhs : `Relation` The other relation the operation will act on.
Returns:	min_rows : `int` Minimum number of rows the new relation would have.

apply(lhs: lsst.daf.relation._relation.Relation, rhs: lsst.daf.relation._relation.Relation) → lsst.daf.relation._relation.Relation¶

Create a new relation that represents the action of this operation on a pair of existing relations.

Parameters:	lhs : `Relation` One relation the operation will act on. rhs : `Relation` The other relation the operation will act on.
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 a `BinaryOperationRelation` holding this operation (or even a similar one) if the operation was inserted earlier in the tree via commutation relations.
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).