org.apache.hadoop.hive.ql.lib

Class LevelOrderWalker

java.lang.Object

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

org.apache.hadoop.hive.ql.lib.LevelOrderWalker

All Implemented Interfaces:

GraphWalker

public class LevelOrderWalker
extends DefaultGraphWalker

This is a level-wise walker implementation which dispatches the node in the order that the node will only get dispatched after all the parents are dispatched. Each node will be accessed once while it could be dispatched multiple times. e.g., for a lineage generator with operator tree, 2 levels of current node's ancestors need to keep in the operator stack. FIL(2) FIL(4) | | RS(3) RS(5) \ / JOIN(7) The join lineage needs to be called twice for JOIN(7) node with different operator ancestors.

Field Summary

Fields inherited from class org.apache.hadoop.hive.ql.lib.DefaultGraphWalker

dispatcher, opQueue, opStack, retMap, toWalk

Constructor Summary

Constructors

Constructor and Description
LevelOrderWalker(Dispatcher disp) Constructor with keeping all the ancestors in the operator stack during dispatching.
LevelOrderWalker(Dispatcher disp, int numLevels) Constructor with specified number of ancestor levels to keep in the operator stack during dispatching.

Method Summary

Modifier and Type	Method and Description
void	setNodeTypes(Class<? extends Node>... nodeTypes)
void	startWalking(Collection<Node> startNodes, HashMap<Node,Object> nodeOutput) starting point for walking.

Methods inherited from class org.apache.hadoop.hive.ql.lib.DefaultGraphWalker

dispatch, dispatchAndReturn, getDispatchedList, walk

Methods inherited from class java.lang.Object

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

Constructor Detail

LevelOrderWalker

public LevelOrderWalker(Dispatcher disp)

Constructor with keeping all the ancestors in the operator stack during dispatching.

Parameters:

disp - Dispatcher to call for each op encountered

LevelOrderWalker

public LevelOrderWalker(Dispatcher disp,
                        int numLevels)

Constructor with specified number of ancestor levels to keep in the operator stack during dispatching.

Parameters:

disp - Dispatcher to call for each op encountered

numLevels - Number of ancestor levels

Method Detail

setNodeTypes

public void setNodeTypes(Class<? extends Node>... nodeTypes)

startWalking

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

starting point for walking.

Specified by:

startWalking in interface GraphWalker

Overrides:

startWalking in class DefaultGraphWalker

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