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package oracle.toplink.essentials.internal.parsing;
import java.util.Iterator;
import java.util.List;
import java.util.ArrayList;
import oracle.toplink.essentials.expressions.*;
import oracle.toplink.essentials.internal.expressions.ConstantExpression;
import oracle.toplink.essentials.internal.queryframework.ReportItem;
import oracle.toplink.essentials.queryframework.ReportQuery;
/**
* INTERNAL
* <p><b>Purpose</b>: Represent an EXISTS subquery.
*/
public class ExistsNode extends Node {
/** True in case of a NOT EXISTS (...) query. */
private boolean notIndicated = false;
/**
* Return a new ExistsNode.
*/
public ExistsNode() {
super();
}
/**
* INTERNAL
* Validate node and calculate its type.
* Change subquery SELECT clause.
*/
public void validate(ParseTreeContext context) {
if (left != null) {
// change SELECT clause of subquery
SubqueryNode subqueryNode = (SubqueryNode)getLeft();
// validate changed subquery
subqueryNode.validate(context);
TypeHelper typeHelper = context.getTypeHelper();
setType(typeHelper.getBooleanType());
}
}
/**
* INTERNAL
* Generate the TopLink expression for this node
*/
public Expression generateExpression(GenerationContext context) {
SubqueryNode subqueryNode = (SubqueryNode)getLeft();
ReportQuery reportQuery = subqueryNode.getReportQuery(context);
// Replace the SELECT clause of the exists subquery by SELECT 1 to
// avoid problems with databases not supporting mutiple columns in the
// subquery SELECT clause in SQL.
// The original select clause expressions might include relationship
// navigations which should result in FK joins in the generated SQL,
// e.g. ... EXISTS (SELECT o.customer FROM Order o ...). Add the
// select clause expressions as non fetch join attributes to the
// ReportQuery representing the subquery. This make sure the FK joins
// get generated.
List items = reportQuery.getItems();
for (Iterator i = items.iterator(); i.hasNext();) {
ReportItem item = (ReportItem)i.next();
Expression expr = item.getAttributeExpression();
reportQuery.addNonFetchJoinedAttribute(expr);
}
reportQuery.clearItems();
Expression one = new ConstantExpression(new Integer(1), new ExpressionBuilder());
reportQuery.addItem("one", one);
reportQuery.dontUseDistinct();
Expression expr = context.getBaseExpression();
return notIndicated() ? expr.notExists(reportQuery) :
expr.exists(reportQuery);
}
/**
* INTERNAL
* Indicate if a NOT was found in the WHERE clause.
* Examples: WHERE ... NOT EXISTS(...)
*/
public void indicateNot() {
notIndicated = true;
}
public boolean notIndicated() {
return notIndicated;
}
}