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

java.lang.Object
  extended byorg.apache.derby.impl.sql.compile.VerifyAggregateExpressionsVisitor
All Implemented Interfaces:
Visitor

public class VerifyAggregateExpressionsVisitor
extends java.lang.Object
implements Visitor

If a RCL (SELECT list) contains an aggregate, then we must verify that the RCL (SELECT list) is valid. For ungrouped queries, the RCL must be composed entirely of valid aggregate expressions - in this case, no column references outside of an aggregate. For grouped aggregates, the RCL must be composed of grouping columns or valid aggregate expressions - in this case, the only column references allowed outside of an aggregate are grouping columns.

Author:
jamie, from code written by jerry

Field Summary
private  GroupByList groupByList
           
 
Constructor Summary
VerifyAggregateExpressionsVisitor(GroupByList groupByList)
           
 
Method Summary
 boolean skipChildren(Visitable node)
          Don't visit children under an aggregate
 boolean stopTraversal()
          Method that is called to see if query tree traversal should be stopped before visiting all nodes.
 Visitable visit(Visitable node)
          Verify that this expression is ok for an aggregate query.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

groupByList

private GroupByList groupByList
Constructor Detail

VerifyAggregateExpressionsVisitor

public VerifyAggregateExpressionsVisitor(GroupByList groupByList)
Method Detail

visit

public Visitable visit(Visitable node)
                throws StandardException
Verify that this expression is ok for an aggregate query.

Specified by:
visit in interface Visitor
Parameters:
node - the node to process
Returns:
me
Throws:
StandardException - on ColumnReferernce not in group by list, ValueNode or JavaValueNode that isn't under an aggregate

skipChildren

public boolean skipChildren(Visitable node)
Don't visit children under an aggregate

Specified by:
skipChildren in interface Visitor
Parameters:
node - the node to process
Returns:
true/false

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

Built on Tue 2006-10-10 19:23:47+0200, from revision exported

Apache Derby V10.1 Engine Documentation - Copyright © 1997,2005 The Apache Software Foundation or its licensors, as applicable.