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java.lang.Objectorg.apache.derby.impl.sql.compile.BaseTableNumbersVisitor
public class BaseTableNumbersVisitor
Walk through a subtree and build a list of the assigned numbers for all tables that exist in that subtree. We do this by looking for any column references in the subtree and, for each column reference, we walk down the ColumnReference-ResultColumn chain until we find the the bottom-most table number, which should correspond to a base table.
Field Summary | |
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private int |
columnNumber
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private JBitSet |
tableMap
|
Constructor Summary | |
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BaseTableNumbersVisitor(JBitSet tableMap)
Constructor: takes a JBitSet to use as the holder for any base table numbers found while walking the subtree. |
Method Summary | |
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protected int |
getColumnNumber()
Retrieve the the position of the ColumnReference or ResultColumn for which we most recently found a base table number. |
protected void |
reset()
Reset the state of this visitor. |
protected void |
setTableMap(JBitSet tableMap)
Set a new JBitSet to serve as the holder for base table numbers we find while walking. |
boolean |
skipChildren(Visitable node)
Method that is called to indicate whether we should skip all nodes below this node for traversal. |
boolean |
stopTraversal()
Method that is called to see if query tree traversal should be stopped before visiting all nodes. |
Visitable |
visit(Visitable node)
This is the default visit operation on a QueryTreeNode. |
boolean |
visitChildrenFirst(Visitable node)
Method that is called to see if visit() should be called on
the children of node before it is called on node itself. |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
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private JBitSet tableMap
private int columnNumber
Constructor Detail |
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public BaseTableNumbersVisitor(JBitSet tableMap)
tableMap
- JBitSet into which we put the table numbers we find.Method Detail |
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protected void setTableMap(JBitSet tableMap)
tableMap
- JBitSet into which we put the table numbers we find.protected void reset()
protected int getColumnNumber()
public Visitable visit(Visitable node) throws StandardException
Visitor
Visitors will overload this method by implementing a version with a signature that matches a specific type of node. For example, if I want to do something special with aggregate nodes, then that Visitor will implement a visit(AggregateNode node) method which does the aggregate specific processing.
visit
in interface Visitor
node
- the node to process
StandardException
- may be throw an error
as needed by the visitor (i.e. may be a normal error
if a particular node is found, e.g. if checking
a group by, we don't expect to find any ColumnReferences
that aren't under an AggregateNode -- the easiest
thing to do is just throw an error when we find the
questionable node).Visitor.visit(org.apache.derby.iapi.sql.compile.Visitable)
public boolean skipChildren(Visitable node)
Visitor
Differs from stopTraversal() in that it only affects subtrees, rather than the entire traversal.
skipChildren
in interface Visitor
node
- the node to process
Visitor.skipChildren(org.apache.derby.iapi.sql.compile.Visitable)
public boolean stopTraversal()
Visitor
stopTraversal
in interface Visitor
Visitor.stopTraversal()
public boolean visitChildrenFirst(Visitable node)
Visitor
visit()
should be called on
the children of node
before it is called on node
itself.
If this method always returns true
, the visitor will walk the
tree bottom-up. If it always returns false
, the tree is visited
top-down.
visitChildrenFirst
in interface Visitor
node
- the top node of a sub-tree about to be visited
true
if node
's children should be visited
before node
, false
otherwiseVisitor.visitChildrenFirst(org.apache.derby.iapi.sql.compile.Visitable)
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Built on Thu 2011-03-10 11:54:14+0000, from revision ??? | ||||||||
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