#190 - Test and fix for fetch joins with scalar selects

CHANGELOG.md

@@ -16,6 +16,7 @@ Not yet released
 * Support enum and entity type literal like the JPA spec says
 * Introduction of `@MappingCorrelatedSimple` for simple correlations
 * Allow empty correlation result with `JOIN` fetch strategy
+* Support for join fetching with scalar selects
 
 ### Bug fixes
 

core/impl/src/main/java/com/blazebit/persistence/impl/AbstractCommonQueryBuilder.java

@@ -159,6 +159,8 @@ public abstract class AbstractCommonQueryBuilder<QueryResultType, BuilderType, S
     protected String cachedExternalQueryString;
     protected boolean hasGroupBy = false;
     protected boolean needsCheck = true;
+    // Fetch owner's are evaluated during implicit joining
+    protected Map<JoinNode, Boolean> fetchOwners = new HashMap<>();
 
     private boolean checkSetBuilderEnded = true;
     private boolean implicitJoinsApplied = false;
@@ -1392,6 +1394,12 @@ public void visit(JoinNode node) {
         selectManager.acceptVisitor(joinVisitor);
         joinVisitor.setJoinRequired(true);
 
+        // Only the main query does has fetch owners
+        if (isMainQuery) {
+            fetchOwners.clear();
+            selectManager.collectFetchOwners(fetchOwners);
+        }
+
         joinVisitor.setFromClause(ClauseType.WHERE);
         whereManager.acceptVisitor(joinVisitor);
         joinVisitor.setFromClause(ClauseType.GROUP_BY);
@@ -1818,7 +1826,7 @@ protected void appendSelectClause(StringBuilder sbSelectFrom) {
 
     protected List<String> appendFromClause(StringBuilder sbSelectFrom, boolean externalRepresentation) {
         List<String> whereClauseConjuncts = new ArrayList<>();
-        joinManager.buildClause(sbSelectFrom, EnumSet.noneOf(ClauseType.class), null, false, externalRepresentation, whereClauseConjuncts, explicitVersionEntities);
+        joinManager.buildClause(sbSelectFrom, EnumSet.noneOf(ClauseType.class), null, false, externalRepresentation, whereClauseConjuncts, explicitVersionEntities, fetchOwners);
         return whereClauseConjuncts;
     }
 

core/impl/src/main/java/com/blazebit/persistence/impl/AbstractFullQueryBuilder.java

@@ -176,17 +176,10 @@ private void checkEntityId(Object entityId) {
         return (FullQueryBuilder<Y, ?>) this;
     }
 
-    private void checkFetchJoinAllowed() {
-        if (selectManager.getSelectInfos().size() > 0) {
-            throw new IllegalStateException("Fetch joins are only possible if the root entity is selected");
-        }
-    }
-
     @Override
     @SuppressWarnings("unchecked")
     public X fetch(String path) {
         prepareForModification();
-        checkFetchJoinAllowed();
         verifyBuilderEnded();
         joinManager.implicitJoin(expressionFactory.createPathExpression(path), true, null, null, false, false, true, true);
         return (X) this;
@@ -196,7 +189,6 @@ public X fetch(String path) {
     @SuppressWarnings("unchecked")
     public X fetch(String... paths) {
         prepareForModification();
-        checkFetchJoinAllowed();
         verifyBuilderEnded();
 
         for (String path : paths) {
@@ -262,10 +254,6 @@ private X join(String path, String alias, JoinType type, boolean fetch, boolean
             throw new IllegalArgumentException("Empty alias");
         }
 
-        if (fetch == true) {
-            checkFetchJoinAllowed();
-        }
-
         verifyBuilderEnded();
         joinManager.join(path, alias, type, fetch, defaultJoin);
         return (X) this;

core/impl/src/main/java/com/blazebit/persistence/impl/BaseSubqueryBuilderImpl.java

@@ -72,7 +72,7 @@ public Set<Expression> getCorrelatedExpressions() {
     public T getResult() {
         return result;
     }
-    
+
     protected BaseFinalSetOperationSubqueryBuilderImpl<T, ?> createFinalSetOperationBuilder(SetOperationType operator, boolean nested, boolean isSubquery) {
         SubqueryBuilderImpl<?> newInitiator = finalSetOperationBuilder == null ? null : finalSetOperationBuilder.getInitiator();
         return createFinalSetOperationBuilder(operator, nested, isSubquery, newInitiator);

core/impl/src/main/java/com/blazebit/persistence/impl/FinalSetOperationCTECriteriaBuilderImpl.java

@@ -31,6 +31,11 @@ public FinalSetOperationCTECriteriaBuilderImpl(MainQuery mainQuery, Class<T> cla
         super(mainQuery, clazz, result, operator, nested, listener, initiator);
     }
 
+    @Override
+    protected void applyImplicitJoins() {
+        // There is nothing to do here for final builders as they don't have any nodes
+    }
+
     @Override
     public T end() {
         subListener.verifyBuilderEnded();

core/impl/src/main/java/com/blazebit/persistence/impl/FinalSetOperationCriteriaBuilderImpl.java

@@ -31,4 +31,9 @@ public class FinalSetOperationCriteriaBuilderImpl<T> extends BaseFinalSetOperati
     public FinalSetOperationCriteriaBuilderImpl(MainQuery mainQuery, boolean isMainQuery, Class<T> clazz, SetOperationType operator, boolean nested, BuilderListener<Object> listener) {
         super(mainQuery, isMainQuery, clazz, operator, nested, listener, null);
     }
+
+    @Override
+    protected void applyImplicitJoins() {
+        // There is nothing to do here for final builders as they don't have any nodes
+    }
 }

core/impl/src/main/java/com/blazebit/persistence/impl/FinalSetOperationSubqueryBuilderImpl.java

@@ -31,6 +31,11 @@ public FinalSetOperationSubqueryBuilderImpl(MainQuery mainQuery, T result, SetOp
         super(mainQuery, result, operator, nested, listener, initiator);
     }
 
+    @Override
+    protected void applyImplicitJoins() {
+        // There is nothing to do here for final builders as they don't have any nodes
+    }
+
     @Override
     public T end() {
         subListener.verifySubqueryBuilderEnded();