Class AbstractConverter

All Implemented Interfaces:
Cloneable, RelOptNode, Converter, RelNode

public class AbstractConverter
extends ConverterImpl
Converts a relational expression to any given output convention.

Unlike most Converters, an abstract converter is always abstract. You would typically create an AbstractConverter when it is necessary to transform a relational expression immediately; later, rules will transform it into relational expressions which can be implemented.

If an abstract converter cannot be satisfied immediately (because the source subset is abstract), the set is flagged, so this converter will be expanded as soon as a non-abstract relexp is added to the set.