Class RepeatUnion

All Implemented Interfaces:
Cloneable, RelOptNode, RelNode
Direct Known Subclasses:
EnumerableRepeatUnion, LogicalRepeatUnion

public abstract class RepeatUnion
extends BiRel
Relational expression that computes a repeat union (recursive union in SQL terminology).

This operation is executed as follows:

  • Evaluate the left input (i.e., seed relational expression) once. For UNION (but not UNION ALL), discard duplicated rows.
  • Evaluate the right input (i.e., iterative relational expression) over and over until it produces no more results (or until an optional maximum number of iterations is reached). For UNION (but not UNION ALL), discard duplicated results.

NOTE: The current API is experimental and subject to change without notice.