Class UnionEliminatorRule

  extended by org.eigenbase.relopt.RelOptRule
      extended by org.eigenbase.rel.rules.UnionEliminatorRule

public class UnionEliminatorRule
extends RelOptRule

UnionEliminatorRule checks to see if its possible to optimize a Union call by eliminating the Union operator altogether in the case the call consists of only one input.

Feb 4, 2005
$Id: //open/dev/farrago/src/org/eigenbase/rel/rules/ $
Wael Chatila

Field Summary
static UnionEliminatorRule instance
Fields inherited from class org.eigenbase.relopt.RelOptRule
ANY, description, operands
Constructor Summary
private UnionEliminatorRule()
          Creates a UnionEliminatorRule.
Method Summary
 void onMatch(RelOptRuleCall call)
          Receives notification about a rule match.
Methods inherited from class org.eigenbase.relopt.RelOptRule
convert, equals, equals, getOperand, getOperands, getOutConvention, getOutTrait, hashCode, matches, mergeTraitsAndConvert, mergeTraitsAndConvert, toString
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail


public static final UnionEliminatorRule instance
Constructor Detail


private UnionEliminatorRule()
Creates a UnionEliminatorRule.

Method Detail


public void onMatch(RelOptRuleCall call)
Description copied from class: RelOptRule
Receives notification about a rule match. At the time that this method is called, call.rels holds the set of relational expressions which match the operands to the rule; call.rels[0] is the root expression.

Typically a rule would check that the nodes are valid matches, creates a new expression, then calls back RelOptRuleCall.transformTo(org.eigenbase.rel.RelNode) to register the expression.

Specified by:
onMatch in class RelOptRule
call - Rule call
See Also: