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

Fields

Modifier and Type
Field and Description


private boolean
hasVariant 


private boolean
ignoreParameters 


private int
variantType 

Constructor Summary

Constructors

Constructor and Description
HasVariantValueNodeVisitor() Construct a visitor
HasVariantValueNodeVisitor(int variantType, boolean ignoreParameters) Construct a visitor.

Method Summary

Modifier and Type	Method and Description
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