/*******************************************************************************
* Copyright (c) 1998, 2008 Oracle. All rights reserved.
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
* which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
* and the Eclipse Distribution License is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* Contributors:
* Oracle - initial API and implementation from Oracle TopLink
******************************************************************************/
package org.eclipse.persistence.internal.jpa.parsing;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import org.eclipse.persistence.queries.*;
import org.eclipse.persistence.expressions.Expression;
import org.eclipse.persistence.descriptors.ClassDescriptor;
/**
* INTERNAL:
* <p><b>Purpose</b>: Represent a SELECT
* <p><b>Responsibilities</b>:<ul>
* <li> Hold the distinct status
* <li> Modify a query based on the contents
* </ul>
*
* <p>The SELECT statement determines the return type of an EJBQL query.
* The SELECT may also determine the distinct state of a query
*
* A SELECT can be one of the following:
* <pre>
* 1. SELECT OBJECT(someObject)... This query will return a collection of objects
* 2. SELECT anObject.anAttribute ... This will return a collection of anAttribute
* 3. SELECT <aggregateFunction> ... This will return a single value
* The allowable aggregateFunctions are: AVG, COUNT, MAX, MIN, SUM
* SELECT AVG(emp.salary)... Returns the average of all the employees salaries
* SELECT COUNT(emp)... Returns a count of the employees
* SELECT COUNT(emp.firstName)... Returns a count of the employee's firstNames
* SELECT MAX(emp.salary)... Returns the maximum employee salary
* SELECT MIN(emp.salary)... Returns the minimum employee salary
* SELECT SUM(emp.salary)... Returns the sum of all the employees salaries
* </pre>
* @author Jon Driscoll
* @since TopLink 5.0
*/
public class SelectNode extends QueryNode {
private List selectExpressions = new ArrayList();
private boolean distinct = false;
public SelectNode() {
}
public List getSelectExpressions() {
return selectExpressions;
}
public void setSelectExpressions(List exprs) {
selectExpressions = exprs;
}
public boolean usesDistinct() {
return distinct;
}
public void setDistinct(boolean distinct) {
this.distinct = distinct;
}
/**
* Returns a DatabaseQuery instance representing the owning
* ParseTree. This implementation returns a ReadAllQuery for simple SELECT
* queries and a ReportQuery otherwise.
*/
public DatabaseQuery createDatabaseQuery(ParseTreeContext context) {
// TODO: This optimization needs to be revisited because it causes GlassFish issues: 2084 and 2171
// These issues have been solve in GlassFish by always generating a ReportQuery
// The same fix has not been made in Oracle TopLink because it disables some advanced JPA Query Hints
ObjectLevelReadQuery query;
if (isReadAllQuery(context)) {
query = new ReadAllQuery();
} else {
query = new ReportQuery();
}
query.dontUseDistinct(); //gf bug 1395- prevents using distinct unless user specified
return query;
}
/**
* Returns true if the SELECT clause consists of a single expression
* returning the base identification variable of the query and if the base
* variable is defined as a range variable w/o FETCH JOINs.
*/
private boolean isReadAllQuery(ParseTreeContext context) {
if (!isSingleSelectExpression()) {
// multiple expressions in the select clause => ReportQuery
return false;
}
Node node = getFirstSelectExpressionNode();
if (!node.isVariableNode()) {
// Does not select an identification variable (e.g. projection or
// aggregate function) => ReportQuery
return false;
}
String variable = ((VariableNode)node).getCanonicalVariableName();
// Note, the base variable in ParseTreeContext is not yet set =>
// calculate it
String baseVariable = getParseTree().getFromNode().getFirstVariable();
if (!context.isRangeVariable(baseVariable)) {
// Query's base variable is not a range variable.
return false;
}
// Use ReadAllQuery if the variable of the SELECT clause expression is
// the base variable
return baseVariable.equals(variable);
}
/**
* INTERNAL
* Apply this node to the passed query
*/
public void applyToQuery(DatabaseQuery theQuery, GenerationContext context) {
ObjectLevelReadQuery readQuery = (ObjectLevelReadQuery)theQuery;
if (selectExpressions.isEmpty()) {
return;
}
//set the distinct state
//BUG 3168673: Don't set distinct state if we're using Count
if (!(isSingleSelectExpression() && getFirstSelectExpressionNode().isCountNode())) {
// Set the distinct state for the query
if (usesDistinct()) {
getParseTree().setDistinctState(ObjectLevelReadQuery.USE_DISTINCT);
readQuery.setDistinctState(ObjectLevelReadQuery.USE_DISTINCT);
}
}
if (readQuery instanceof ReportQuery) {
ReportQuery reportQuery = (ReportQuery)readQuery;
reportQuery.returnWithoutReportQueryResult();
if (isSingleSelectExpression()) {
reportQuery.returnSingleAttribute();
}
}
SelectGenerationContext selectContext = (SelectGenerationContext)context;
for (Iterator i = selectExpressions.iterator(); i.hasNext();) {
Node node = (Node)i.next();
if (selectingRelationshipField(node, context)) {
selectContext.useOuterJoins();
}
node.applyToQuery(readQuery, context);
selectContext.dontUseOuterJoins();
}
//indicate on the query if "return null if primary key null"
//This means we want nulls returned if we expect an outer join
readQuery.setShouldBuildNullForNullPk(this.hasOneToOneSelected(context));
}
public boolean hasOneToOneSelected(GenerationContext context) {
// Iterate the select expression and return true if one of it has a
// oneToOne selected.
for (Iterator i = selectExpressions.iterator(); i.hasNext();) {
Node node = (Node)i.next();
if (hasOneToOneSelected(node, context)) {
return true;
}
}
return false;
}
/**
* Answer true if there is a one-to-one relationship selected.
* This includes a chain of relationships.
* True: SELECT employee.address FROM ..... //Simple 1:1
* True: SELECT a.b.c.d FROM ..... //where a->b, b->c and c->d are all 1:1.
* False: SELECT OBJECT(employee) FROM ..... //simple SELECT
* False: SELECT phoneNumber.areaCode FROM ..... //direct-to-field
*/
private boolean hasOneToOneSelected(Node node, GenerationContext context) {
//BUG 3240484: Not SELECTing 1:1 if it's in a COUNT
if (node.isCountNode()) {
return false;
}
if (node.isAggregateNode()) {
// delegate to aggregate expression
return hasOneToOneSelected(node.getLeft(), context);
}
if (node.isVariableNode()){
return !nodeRefersToObject(node, context);
}
if (node.isConstructorNode()) {
List args = ((ConstructorNode)node).getConstructorItems();
for (Iterator i = args.iterator(); i.hasNext();) {
Node arg = (Node)i.next();
if (hasOneToOneSelected(arg, context)) {
return true;
}
}
return false;
}
// check whether it is a direct-to-field mapping
return !selectingDirectToField(node, context);
}
/**
* Verify that the selected alias is a valid alias. If it's not valid,
* an Exception will be thrown, likely JPQLException.aliasResolutionException.
*
* Valid: SELECT OBJECT(emp) FROM Employee emp WHERE ...
* Invalid: SELECT OBJECT(badAlias) FROM Employee emp WHERE ...
*/
public void verifySelectedAlias(GenerationContext context) {
for (Iterator i = selectExpressions.iterator(); i.hasNext();) {
Node node = (Node)i.next();
//if the node is a DotNode, there is no selected alias
if (node.isDotNode()) {
return;
}
node.resolveClass(context);
}
}
/**
* Answer true if the variable name given as argument is SELECTed.
*
* True: "SELECT OBJECT(emp) ...." & variableName = "emp"
* False: "SELECT OBJECT(somethingElse) ..." & variableName = "emp"
*/
public boolean isSelected(String variableName) {
for (Iterator i = selectExpressions.iterator(); i.hasNext();) {
Node node = (Node)i.next();
//Make sure we've SELECted a VariableNode
if (node.isVariableNode() &&
((VariableNode)node).getCanonicalVariableName().equals(variableName)) {
return true;
}
}
return false;
}
public boolean isSelectNode() {
return true;
}
/**
* Check the select expression nodes for a path expression starting with a
* unqualified field access and if so, replace it by a qualified field
* access.
*/
public Node qualifyAttributeAccess(ParseTreeContext context) {
for (int i = 0; i < selectExpressions.size(); i++) {
Node item = (Node)selectExpressions.get(i);
selectExpressions.set(i, item.qualifyAttributeAccess(context));
}
return this;
}
/**
* Validate node.
*/
public void validate(ParseTreeContext context) {
for (Iterator i = selectExpressions.iterator(); i.hasNext(); ) {
Node item = (Node)i.next();
item.validate(context);
}
}
/**
* Answer the class associated with my left node.
*/
public Class resolveClass(GenerationContext context) {
return getReferenceClass(context);
}
/**
* Return a EclipseLink expression generated using the left node.
*/
public Expression generateExpression(GenerationContext context) {
return null;
}
/**
* Compute the Reference class for this query.
* @return the class this query is querying for
*/
public Class getReferenceClass(GenerationContext context) {
return getClassOfFirstVariable(context);
}
private Class getClassOfFirstVariable(GenerationContext context) {
Class clazz = null;
String variable = getParseTree().getFromNode().getFirstVariable();
ParseTreeContext parseTreeContext = context.getParseTreeContext();
if (parseTreeContext.isRangeVariable(variable)) {
String schema = parseTreeContext.schemaForVariable(variable);
// variables is defines in a range variable declaration, so there
// is a schema name for this variable
clazz = parseTreeContext.classForSchemaName(schema, context);
} else {
// variable is defined in a JOIN clause, so there is a a defining
// node for the variable
Node path = parseTreeContext.pathForVariable(variable);
clazz = path.resolveClass(context);
}
return clazz;
}
/**
* Answer true if a variable in the IN clause is SELECTed
*/
public boolean isVariableInINClauseSelected(GenerationContext context) {
for (Iterator i = selectExpressions.iterator(); i.hasNext();) {
Node node = (Node)i.next();
if (node.isVariableNode()) {
String variableNameForLeft = ((VariableNode)node).getCanonicalVariableName();
if (!context.getParseTreeContext().isRangeVariable(variableNameForLeft)) {
return true;
}
}
}
return false;
}
/**
* Answer true if this node refers to an object described later in the EJBQL
* True: SELECT p FROM Project p
* False: SELECT p.id FROM Project p
*/
public boolean nodeRefersToObject(Node node, GenerationContext context) {
if (!node.isVariableNode()){
return false;
}
String name = ((VariableNode)node).getCanonicalVariableName();
String alias = context.getParseTreeContext().schemaForVariable(name);
if (alias != null){
ClassDescriptor descriptor = context.getSession().getDescriptorForAlias(alias);
if (descriptor != null){
return true;
}
}
return false;
}
private boolean selectingRelationshipField(Node node, GenerationContext context) {
if ((node == null) || !node.isDotNode()) {
return false;
}
TypeHelper typeHelper = context.getParseTreeContext().getTypeHelper();
Node path = node.getLeft();
AttributeNode attribute = (AttributeNode)node.getRight();
return typeHelper.isRelationship(path.getType(),
attribute.getAttributeName());
}
/**
* Answer true if the SELECT ends in a direct-to-field.
* true: SELECT phone.areaCode
* false: SELECT employee.address
*/
private boolean selectingDirectToField(Node node, GenerationContext context) {
if ((node == null) || !node.isDotNode()) {
return false;
}
return ((DotNode)node).endsWithDirectToField(context);
}
/**
* Returns the first select expression node.
*/
private Node getFirstSelectExpressionNode() {
return selectExpressions.size() > 0 ?
(Node)selectExpressions.get(0) : null;
}
private boolean isSingleSelectExpression() {
return selectExpressions.size() == 1;
}
}