Package org.apache.derby.impl.sql.compile

Class HasVariantValueNodeVisitor

  • All Implemented Interfaces:
    Visitor
    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
    

    

      

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        Field Summary
        

    




    
Fields 

    
Modifier and Type
Field
Description

    

    
private boolean
hasVariant
 

    

    
private boolean
ignoreParameters
 

    

    
private int
variantType
 

  • Method Summary

    All Methods Instance Methods Concrete Methods 
    Modifier and Type Method Description
    (package private) 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

        HasVariantValueNodeVisitor()
        Construct a visitor

      • HasVariantValueNodeVisitor

        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

      • 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

        boolean hasVariant()
        Indicate whether we found the node in question
        Returns:
        true/false