org.apache.derby.impl.sql.compile
Class HasVariantValueNodeVisitor

java.lang.Object
  org.apache.derby.impl.sql.compile.HasVariantValueNodeVisitor

All Implemented Interfaces:

Visitor

public class HasVariantValueNodeVisitor
extends java.lang.Object
implements Visitor

Find out if we have a value node with variant type less than what the caller desires, anywhere below us. Stop traversal as soon as we find one. This is used in two places: one to check the values clause of an insert statement; i.e

 insert into  values (?, 1, foobar());
 
 If all the expressions in the values clause are QUERY_INVARIANT (and an
 exception is made for parameters) then we can cache the results in the
 RowResultNode. This is useful when we have a prepared insert statement which
 is repeatedly executed.
 

 The second place where this is used is to check if a subquery can be
 materialized or not.




See Also:
Qualifier




Field Summary




private  boolean
hasVariant



           



private  boolean
ignoreParameters



           



private  int
variantType



           


 



Constructor Summary
HasVariantValueNodeVisitor()



          Construct a visitor
HasVariantValueNodeVisitor(int variantType,
                           boolean ignoreParameters)



          Construct a visitor.
 



Method Summary




 boolean
hasVariant()



          Indicate whether we found the node in
 question



 boolean
skipChildren(Visitable node)



          Method that is called to indicate whether
 we should skip all nodes below this node
 for traversal.



 boolean
stopTraversal()



          Stop traversal if we found the target node



 Visitable
visit(Visitable node)



          If we have found the target node, we are done.



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





Field Detail



hasVariant
private boolean hasVariant







variantType
private int variantType







ignoreParameters
private boolean ignoreParameters








Constructor Detail



HasVariantValueNodeVisitor
public HasVariantValueNodeVisitor()

Construct a visitor





HasVariantValueNodeVisitor
public HasVariantValueNodeVisitor(int variantType,
                                  boolean ignoreParameters)

Construct a visitor.  Pass in the variant
 type.  We look for nodes that are less
 than or equal to this variant type.  E.g.,
 if the variantType is Qualifier.SCAN_VARIANT,
 then any node that is either VARIANT or
 SCAN_VARIANT will cause the visitor to 
 consider it variant.


Parameters:
variantType - the type of variance we consider
                variant
ignoreParameters - should I ignore parameter nodes?





Method Detail



visit
public Visitable visit(Visitable node)
                throws StandardException

If we have found the target node, we are done.


Specified by:
visit in interface Visitor


Parameters:
node - the node to process
Returns:
me
Throws:
StandardException - on error





skipChildren
public boolean skipChildren(Visitable node)

Description copied from interface: Visitor
Method that is called to indicate whether
 we should skip all nodes below this node
 for traversal.  Useful if we want to effectively
 ignore/prune all branches under a particular 
 node.  
 

 Differs from stopTraversal() in that it
 only affects subtrees, rather than the
 entire traversal.


Specified by:
skipChildren in interface Visitor


Parameters:
node - the node to process
Returns:
true/false





visitChildrenFirst
public boolean visitChildrenFirst(Visitable node)

Description copied from interface: Visitor
Method that is called to see if 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.


Specified by:
visitChildrenFirst in interface Visitor


Parameters:
node - the top node of a sub-tree about to be visited
Returns:
true if node's children should be visited
 before node, false otherwise





stopTraversal
public boolean stopTraversal()

Stop traversal if we found the target node


Specified by:
stopTraversal in interface Visitor



Returns:
true/false





hasVariant
public boolean hasVariant()

Indicate whether we found the node in
 question






Returns:
true/false