PredicateLiteral¶

class lsst.daf.relation.PredicateLiteral(value: bool)¶

A concrete boolean column expression that is a constant True or False.

Attributes Summary

columns_required Columns required by this expression (Set [ ColumnTag ]).

Methods Summary

`as_trivial`()	Attempt to simplify this expression into a constant boolean.
`is_supported_by`(engine)	Test whether the given engine is capable of evaluating this expression.
`literal`(value)	Construct a boolean expression that is a constant `True` or `False`.
`logical_and`()	Return a boolean expression that is the logical AND of the given ones.
`logical_not`()	Return a boolean expression that is the logical NOT of this one.
`logical_or`()	Return a boolean expression that is the logical OR of the given ones.
`reference`(tag)	Construct an expression that refers to a boolean column in a relation.

Attributes Documentation

columns_required¶

Columns required by this expression (Set [ ColumnTag ]).

This includes columns required by expressions nested within this one.

Methods Documentation

as_trivial() → bool¶

Attempt to simplify this expression into a constant boolean.

Returns:	trivial : `bool` or `None` If `True` or `False`, the expression always evaluates to exactly that constant value. If `None`, the expression is nontrivial (or at least could not easily be simplified into a trivial expression).

is_supported_by(engine: Engine) → bool¶

Test whether the given engine is capable of evaluating this expression.

Parameters:	engine : `Engine` Engine to test.
Returns:	supported : `bool` Whether the engine supports this expression and all expressions nested within it.

classmethod literal(value: bool) → lsst.daf.relation._columns._predicate.PredicateLiteral¶

Construct a boolean expression that is a constant True or False.

Parameters:	value : `bool` Value for the expression.
Returns:	literal : `PredicateLiteral` A boolean column expression set to the given value.

logical_and() → lsst.daf.relation._columns._predicate.Predicate¶

Return a boolean expression that is the logical AND of the given ones.

Parameters:	*operands : `Predicate` Existing boolean expressions to AND together.
Returns:	logical_and : `Predicate` Logical AND expression. If no operands are provided, a `PredicateLiteral` for `True` is returned. If one operand is provided, it is returned directly.

logical_not() → lsst.daf.relation._columns._predicate.LogicalNot¶

Return a boolean expression that is the logical NOT of this one.

Returns:	logical_not : `Predicate` Logical NOT expression.

logical_or() → lsst.daf.relation._columns._predicate.Predicate¶

Return a boolean expression that is the logical OR of the given ones.

Parameters:	*operands : `Predicate` Existing boolean expressions to OR together.
Returns:	logical_and : `Predicate` Logical OR expression. If no operands are provided, a `PredicateLiteral` for `False` is returned. If one operand is provided, it is returned directly.

classmethod reference(tag: lsst.daf.relation._columns._tag.ColumnTag) → lsst.daf.relation._columns._predicate.PredicateReference¶

Construct an expression that refers to a boolean column in a relation.

Parameters:	tag : `ColumnTag` Identifier for the column to reference.
Returns:	reference : `PredicateReference` A column expression that refers the given relation column.