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

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

All Implemented Interfaces:

org.apache.derby.iapi.sql.compile.Visitor

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public class HasVariantValueNodeVisitor

extends java.lang.Object

implements org.apache.derby.iapi.sql.compile.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.














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(org.apache.derby.iapi.sql.compile.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



 org.apache.derby.iapi.sql.compile.Visitable
visit(org.apache.derby.iapi.sql.compile.Visitable node)



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


 


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.









Method Detail




visit
public org.apache.derby.iapi.sql.compile.Visitable visit(org.apache.derby.iapi.sql.compile.Visitable node)
                                                  throws org.apache.derby.iapi.error.StandardException

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


Specified by:
visit in interface org.apache.derby.iapi.sql.compile.Visitor








skipChildren
public boolean skipChildren(org.apache.derby.iapi.sql.compile.Visitable node)

Description copied from interface: org.apache.derby.iapi.sql.compile.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 org.apache.derby.iapi.sql.compile.Visitor








stopTraversal
public boolean stopTraversal()

Stop traversal if we found the target node


Specified by:
stopTraversal in interface org.apache.derby.iapi.sql.compile.Visitor








hasVariant
public boolean hasVariant()

Indicate whether we found the node in
 question

















  

  
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