org.apache.derby.impl.sql.execute.xplain

Class XPLAINSystemTableVisitor

java.lang.Object

org.apache.derby.impl.sql.execute.xplain.XPLAINSystemTableVisitor

All Implemented Interfaces:

XPLAINVisitor

public class XPLAINSystemTableVisitor
extends java.lang.Object
implements XPLAINVisitor

This is the Visitor, which explains the information and stores the statistics in the system catalogs. It traverses the result set statistics tree and extracts the information.

Constructor Summary

Constructors

Constructor and Description
XPLAINSystemTableVisitor()

Method Summary

Modifier and Type	Method and Description
void	doXPLAIN(RunTimeStatistics rss, Activation activation) the interface method, which gets called by the Top-ResultSet, which starts the tree traversal.
void	reset() This method resets the visitor.
void	setNumberOfChildren(int noChildren) this method only stores the current number of children of the current explained node.
void	visit(ResultSetStatistics statistics) Visit this node, calling back to it to get details.

Methods inherited from class java.lang.Object

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

Constructor Detail

XPLAINSystemTableVisitor

public XPLAINSystemTableVisitor()

Method Detail

setNumberOfChildren

public void setNumberOfChildren(int noChildren)

this method only stores the current number of children of the current explained node. The child nodes then can re-use this information.

Specified by:

setNumberOfChildren in interface XPLAINVisitor

Parameters:

noChildren - the number of children of the current explained node.

visit

public void visit(ResultSetStatistics statistics)

Visit this node, calling back to it to get details. This method visits the RS Statisitcs node, calling back to the node to get detailed descriptor information about it.

Specified by:

visit in interface XPLAINVisitor

Parameters:

statistics - the statistics, which want to get explained.

reset

public void reset()

This method resets the visitor. Gets called right before explanation to make sure all needed objects exist and are up to date and the lists are cleared

Specified by:

reset in interface XPLAINVisitor

doXPLAIN

public void doXPLAIN(RunTimeStatistics rss,
                     Activation activation)
              throws StandardException

the interface method, which gets called by the Top-ResultSet, which starts the tree traversal.

Specified by:

doXPLAIN in interface XPLAINVisitor

Throws:

StandardException