org.apache.pig.impl.plan.optimizer
Class Transformer<O extends Operator,P extends OperatorPlan<O>>
java.lang.Object
org.apache.pig.impl.plan.PlanVisitor<O,P>
org.apache.pig.impl.plan.optimizer.Transformer<O,P>
- Direct Known Subclasses:
- LogicalTransformer
public abstract class Transformer<O extends Operator,P extends OperatorPlan<O>>
- extends PlanVisitor<O,P>
Transformer represents one tranform that the optimizer can
apply to a graph. This class is a special case of a PlanVisitor,so it
can navigate the plan.
Method Summary |
abstract boolean |
check(List<O> nodes)
check if the transform should be done. |
abstract void |
reset()
Reset any internal state after the transformation. |
abstract void |
transform(List<O> nodes)
Transform the tree |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Transformer
protected Transformer(P plan,
PlanWalker<O,P> walker)
- Parameters:
plan
- OperatorPlan to be optimized.
check
public abstract boolean check(List<O> nodes)
throws OptimizerException
- check if the transform should be done. If this is being called then
the pattern matches, but there may be other criteria that must be met
as well.
- Parameters:
nodes
- - List of nodes declared in transform ($1 = nodes[0],
etc.) Remember that somes entries in node[] may be NULL since they may
not be created until after the transform.
- Returns:
- true if the transform should be done.
- Throws:
OptimizerException
transform
public abstract void transform(List<O> nodes)
throws OptimizerException
- Transform the tree
- Parameters:
nodes
- - List of nodes declared in transform ($1 = nodes[0],
etc.) This call must destruct any nodes that are being removed as part
of the transform and remove them from the nodes vector and construct
any that are being created as part of the transform and add them at the
appropriate point to the nodes vector.
- Throws:
OptimizerException
reset
public abstract void reset()
throws OptimizerException
- Reset any internal state after the transformation.
- Throws:
OptimizerException
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