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java.lang.Objectorg.apache.derby.impl.sql.compile.SubstituteExpressionVisitor
class SubstituteExpressionVisitor
Replaces a source expression with a target expression.
Field Summary | |
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private java.lang.Class |
skipOverClass
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private ValueNode |
source
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private ValueNode |
target
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Constructor Summary | |
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SubstituteExpressionVisitor(ValueNode s,
ValueNode t,
java.lang.Class skipThisClass)
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Method Summary | |
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ValueNode |
getSource()
used by GroupByNode to process expressions by complexity level. |
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 ValueNode source
private ValueNode target
private java.lang.Class skipOverClass
Constructor Detail |
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SubstituteExpressionVisitor(ValueNode s, ValueNode t, java.lang.Class skipThisClass)
Method Detail |
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public ValueNode getSource()
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).public boolean stopTraversal()
Visitor
stopTraversal
in interface Visitor
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
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
otherwise
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Built on Thu 2010-12-23 20:49:13+0000, from revision ??? | ||||||||
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