Apache Derby Database Engine and Embedded JDBC Driver 10.17.1.0 · org.apache.derby.impl.sql.compile.OffsetOrderVisitor

Modifier and Type	Field and Description
private static final Comparator<QueryTreeNode>	COMPARATOR Comparator that orders nodes by ascending begin offset.
private final int	highOffset
private final int	lowOffset
private final Class<T>	nodeClass
private final TreeSet<T>	nodes

Access	Constructor and Description
pack-priv	OffsetOrderVisitor(Class<T> the type of nodes to collect nodeClass, int the lowest begin offset to accept (inclusive) low, int the highest end offset to accept (exclusive) high) Create a new `OffsetOrderVisitor` that collects nodes of the specified type.

Method Summary

Modifier and Type	Method and Description
pack-priv SortedSet<T>	getNodes()
public boolean	skipChildren(Visitable the node to process node) Implements org.apache.derby.iapi.sql.compile.Visitor.skipChildren. Method that is called to indicate whether we should skip all nodes below this node for traversal.
public boolean	stopTraversal() Implements org.apache.derby.iapi.sql.compile.Visitor.stopTraversal. Method that is called to see if query tree traversal should be stopped before visiting all nodes.
public Visitable	visit(Visitable the node to process node) Implements org.apache.derby.iapi.sql.compile.Visitor.visit. This is the default visit operation on a QueryTreeNode.
public boolean	visitChildrenFirst(Visitable the top node of a sub-tree about to be visited node) Implements org.apache.derby.iapi.sql.compile.Visitor.visitChildrenFirst. Method that is called to see if `visit()` should be called on the children of `node` before it is called on `node` itself.

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll toString wait wait wait

COMPARATOR	back to summary
private static final Comparator<QueryTreeNode> COMPARATOR Comparator that orders nodes by ascending begin offset.

highOffset	back to summary
private final int highOffset

lowOffset	back to summary
private final int lowOffset

nodeClass	back to summary
private final Class<T> nodeClass

nodes	back to summary
private final TreeSet<T> nodes

OffsetOrderVisitor	back to summary
pack-priv OffsetOrderVisitor(Class<T> nodeClass, int low, int high) Create a new `OffsetOrderVisitor` that collects nodes of the specified type. The nodes must have begin offset and end offset in the range given by the `low` and `high` parameters. Parameters nodeClass:Class<T> the type of nodes to collect low:int the lowest begin offset to accept (inclusive) high:int the highest end offset to accept (exclusive)

Method Detail

getNodes	back to summary
pack-priv SortedSet<T> getNodes()

skipChildren	back to summary
public boolean skipChildren(Visitable node) throws StandardException Implements org.apache.derby.iapi.sql.compile.Visitor.skipChildren. Doc from org.apache.derby.iapi.sql.compile.Visitor.skipChildren. 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. Parameters node:Visitable the node to process Returns:boolean true/false Annotations @Override

skipChildren

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public boolean skipChildren(Visitable node) throws StandardException

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

Doc from org.apache.derby.iapi.sql.compile.Visitor.skipChildren.

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.

Parameters

node:Visitable: the node to process

Returns:boolean

true/false

Annotations

@Override

stopTraversal	back to summary
public boolean stopTraversal() Implements org.apache.derby.iapi.sql.compile.Visitor.stopTraversal. Doc from org.apache.derby.iapi.sql.compile.Visitor.stopTraversal. Method that is called to see if query tree traversal should be stopped before visiting all nodes. Useful for short circuiting traversal if we already know we are done. Returns:boolean true/false Annotations @Override

stopTraversal

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public boolean stopTraversal()

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

Doc from org.apache.derby.iapi.sql.compile.Visitor.stopTraversal.

Method that is called to see if query tree traversal should be stopped before visiting all nodes. Useful for short circuiting traversal if we already know we are done.

Returns:boolean

true/false

Annotations

@Override

visit	back to summary
public Visitable visit(Visitable node) throws StandardException Implements org.apache.derby.iapi.sql.compile.Visitor.visit. Doc from org.apache.derby.iapi.sql.compile.Visitor.visit. This is the default visit operation on a QueryTreeNode. It just returns the node. This will typically suffice as the default visit operation for most visitors unless the visitor needs to count the number of nodes visited or something like that. 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. Parameters node:Visitable the node to process Returns:Visitable a query tree node. Often times this is the same node that was passed in, but Visitors that replace nodes with other nodes will use this to return the new replacement node. Annotations @Override Exceptions 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).

visit

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public Visitable visit(Visitable node) throws StandardException

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

Doc from org.apache.derby.iapi.sql.compile.Visitor.visit.

This is the default visit operation on a QueryTreeNode. It just returns the node. This will typically suffice as the default visit operation for most visitors unless the visitor needs to count the number of nodes visited or something like that.

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.

Parameters

node:Visitable: the node to process

Returns:Visitable

a query tree node. Often times this is the same node that was passed in, but Visitors that replace nodes with other nodes will use this to return the new replacement node.

Annotations

@Override

Exceptions

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).

visitChildrenFirst back to summary

visitChildrenFirst	back to summary
public boolean visitChildrenFirst(Visitable node) Implements org.apache.derby.iapi.sql.compile.Visitor.visitChildrenFirst. Doc from org.apache.derby.iapi.sql.compile.Visitor.visitChildrenFirst. 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. Parameters node:Visitable the top node of a sub-tree about to be visited Returns:boolean `true` if `node`'s children should be visited before `node`, `false` otherwise Annotations @Override

public boolean visitChildrenFirst(Visitable node)

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

Doc from org.apache.derby.iapi.sql.compile.Visitor.visitChildrenFirst.

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.

Parameters

node:Visitable: the top node of a sub-tree about to be visited

Returns:boolean

true if node's children should be visited before node, false otherwise

Annotations

@Override

pack-priv Class OffsetOrderVisitor<T extends QueryTreeNode>

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