org.apache.hadoop.hive.ql.lib
Class DefaultGraphWalker

java.lang.Object
  org.apache.hadoop.hive.ql.lib.DefaultGraphWalker

All Implemented Interfaces:

GraphWalker

Direct Known Subclasses:

ColumnPruner.ColumnPrunerWalker, GenMapRedWalker, PreOrderWalker

public class DefaultGraphWalker
extends Object
implements GraphWalker

base class for operator graph walker this class takes list of starting ops and walks them one by one. it maintains list of walked operators (dispatchedList) and a list of operators that are discovered but not yet dispatched

Field Summary

protected Stack<Node>

opStack

Constructor Summary

DefaultGraphWalker(Dispatcher disp)
Constructor.

Method Summary

void	dispatch(Node nd, Stack<Node> ndStack) Dispatch the current operator.
Set<Node>	getDispatchedList()
List<Node>	getToWalk()
void	startWalking(Collection<Node> startNodes, HashMap<Node,Object> nodeOutput) starting point for walking.
void	walk(Node nd) walk the current operator and its descendants.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

opStack

protected Stack<Node> opStack

Constructor Detail

DefaultGraphWalker

public DefaultGraphWalker(Dispatcher disp)

Constructor.

Parameters:

disp - dispatcher to call for each op encountered

Method Detail

getToWalk

public List<Node> getToWalk()

Returns:

the toWalk

getDispatchedList

public Set<Node> getDispatchedList()

Returns:

the doneList

dispatch

public void dispatch(Node nd,
                     Stack<Node> ndStack)
              throws SemanticException

Dispatch the current operator.

Parameters:

nd - node being walked

ndStack - stack of nodes encountered

Throws:

SemanticException

startWalking

public void startWalking(Collection<Node> startNodes,
                         HashMap<Node,Object> nodeOutput)
                  throws SemanticException

starting point for walking.

Specified by:

startWalking in interface GraphWalker

Parameters:

startNodes - list of starting operators

nodeOutput - If this parameter is not null, the call to the function returns the map from node to objects returned by the processors.

Throws:

SemanticException

walk

public void walk(Node nd)
          throws SemanticException

walk the current operator and its descendants.

Parameters:

nd - current operator in the graph

Throws:

SemanticException