Class BaseTableNumbersVisitor

java.lang.Object
org.apache.derby.impl.sql.compile.BaseTableNumbersVisitor
All Implemented Interfaces:
Visitor

class BaseTableNumbersVisitor extends Object implements Visitor
Walk through a subtree and build a list of the assigned numbers for all tables that exist in that subtree. We do this by looking for any column references in the subtree and, for each column reference, we walk down the ColumnReference-ResultColumn chain until we find the the bottom-most table number, which should correspond to a base table.
  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    private int
     
    private JBitSet
     
  • Constructor Summary

    Constructors
    Constructor
    Description
    Constructor: takes a JBitSet to use as the holder for any base table numbers found while walking the subtree.
  • Method Summary

    Modifier and Type
    Method
    Description
    protected int
    Retrieve the the position of the ColumnReference or ResultColumn for which we most recently found a base table number.
    protected void
    Reset the state of this visitor.
    protected void
    setTableMap(JBitSet tableMap)
    Set a new JBitSet to serve as the holder for base table numbers we find while walking.
    boolean
    Method that is called to indicate whether we should skip all nodes below this node for traversal.
    boolean
    Method that is called to see if query tree traversal should be stopped before visiting all nodes.
    This is the default visit operation on a QueryTreeNode.
    boolean
    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 Details

    • tableMap

      private JBitSet tableMap
    • columnNumber

      private int columnNumber
  • Constructor Details

    • BaseTableNumbersVisitor

      BaseTableNumbersVisitor(JBitSet tableMap)
      Constructor: takes a JBitSet to use as the holder for any base table numbers found while walking the subtree.
      Parameters:
      tableMap - JBitSet into which we put the table numbers we find.
  • Method Details

    • setTableMap

      protected void setTableMap(JBitSet tableMap)
      Set a new JBitSet to serve as the holder for base table numbers we find while walking.
      Parameters:
      tableMap - JBitSet into which we put the table numbers we find.
    • reset

      protected void reset()
      Reset the state of this visitor.
    • getColumnNumber

      protected int getColumnNumber()
      Retrieve the the position of the ColumnReference or ResultColumn for which we most recently found a base table number.
    • visit

      public Visitable visit(Visitable node) throws StandardException
      Description copied from interface: Visitor
      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.

      Specified by:
      visit in interface Visitor
      Parameters:
      node - the node to process
      Returns:
      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.
      Throws:
      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).
      See Also:
    • 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
      See Also:
    • stopTraversal

      public boolean stopTraversal()
      Description copied from interface: Visitor
      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.
      Specified by:
      stopTraversal in interface Visitor
      Returns:
      true/false
      See Also:
    • 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
      See Also: