From 12732525b55ed31fbde44e3d42ab2c0ad6ff7459 Mon Sep 17 00:00:00 2001
From: Anders Schack-Mulligen <aschackmull@github.com>
Date: Fri, 18 Jul 2025 11:45:45 +0200
Subject: [PATCH 1/3] Java: Allow 2-column join on delta to improve join-order.

---
 java/ql/lib/semmle/code/java/Generics.qll | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/java/ql/lib/semmle/code/java/Generics.qll b/java/ql/lib/semmle/code/java/Generics.qll
index e0204b1beace..fbd979a03694 100644
--- a/java/ql/lib/semmle/code/java/Generics.qll
+++ b/java/ql/lib/semmle/code/java/Generics.qll
@@ -521,7 +521,13 @@ private predicate unificationTargets(RefType t1, Type t2) {
     t2 = a2.getComponentType()
   )
   or
-  exists(ParameterizedType pt1, ParameterizedType pt2, int pos |
+  unificationTargetsParameterized(_, _, t1, t2)
+}
+
+private predicate unificationTargetsParameterized(
+  ParameterizedType pt1, ParameterizedType pt2, RefType t1, RefType t2
+) {
+  exists(int pos |
     unificationTargets(pt1, pt2) and
     t1 = pt1.getTypeArgument(pos) and
     t2 = pt2.getTypeArgument(pos)
@@ -565,10 +571,12 @@ private predicate hasParameterSubstitution(
   GenericType g1, ParameterizedType pt1, GenericType g2, ParameterizedType pt2, TypeVariable v,
   RefType subst
 ) {
-  unificationTargets(pt1, pt2) and
-  exists(int pos | hasSubstitution(pt1.getTypeArgument(pos), pt2.getTypeArgument(pos), v, subst)) and
-  g1 = pt1.getGenericType() and
-  g2 = pt2.getGenericType()
+  exists(RefType t1, RefType t2 |
+    unificationTargetsParameterized(pt1, pt2, t1, t2) and
+    hasSubstitution(t1, t2, v, subst) and
+    g1 = pt1.getGenericType() and
+    g2 = pt2.getGenericType()
+  )
 }
 
 /**

From 7883124abddf3ac73c383df10e9942cd8d0dedb8 Mon Sep 17 00:00:00 2001
From: Anders Schack-Mulligen <aschackmull@github.com>
Date: Fri, 18 Jul 2025 11:47:14 +0200
Subject: [PATCH 2/3] Java: getSourceDeclaration() and getASourceSupertype*()
 commute and this yields much better join-order.

---
 java/ql/src/Likely Bugs/Collections/ContainsTypeMismatch.ql | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/java/ql/src/Likely Bugs/Collections/ContainsTypeMismatch.ql b/java/ql/src/Likely Bugs/Collections/ContainsTypeMismatch.ql
index d1a398d1322c..497aa10cb4de 100644
--- a/java/ql/src/Likely Bugs/Collections/ContainsTypeMismatch.ql	
+++ b/java/ql/src/Likely Bugs/Collections/ContainsTypeMismatch.ql	
@@ -103,8 +103,8 @@ class MismatchedContainerAccess extends MethodCall {
     |
       this.getCallee()
           .getDeclaringType()
-          .getASourceSupertype*()
           .getSourceDeclaration()
+          .getASourceSupertype*()
           .hasQualifiedName(package, type) and
       this.getCallee().getParameter(i).getType() instanceof TypeObject
     )
@@ -119,7 +119,7 @@ class MismatchedContainerAccess extends MethodCall {
       containerAccess(package, type, p, this.getCallee().getSignature(), i)
     |
       t = this.getCallee().getDeclaringType() and
-      t.getASourceSupertype*().getSourceDeclaration() = g and
+      t.getSourceDeclaration().getASourceSupertype*() = g and
       g.hasQualifiedName(package, type) and
       indirectlyInstantiates(t, g, p, result)
     )

From d9f47bdec9ec0ac568c1a447ccf42fe93ad0ccdc Mon Sep 17 00:00:00 2001
From: Anders Schack-Mulligen <aschackmull@github.com>
Date: Fri, 18 Jul 2025 11:48:50 +0200
Subject: [PATCH 3/3] Java: Improve join-order by properly annotating
 haveIntersection.

---
 java/ql/lib/semmle/code/java/Type.qll | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/java/ql/lib/semmle/code/java/Type.qll b/java/ql/lib/semmle/code/java/Type.qll
index aa1cc5fdc7f7..dd646e74285c 100644
--- a/java/ql/lib/semmle/code/java/Type.qll
+++ b/java/ql/lib/semmle/code/java/Type.qll
@@ -1261,14 +1261,21 @@ private Type erase(Type t) {
  *
  * For the definition of the notion of *erasure* see JLS v8, section 4.6 (Type Erasure).
  */
+bindingset[t1, t2]
 overlay[caller?]
-pragma[inline]
+pragma[inline_late]
 predicate haveIntersection(RefType t1, RefType t2) {
   exists(RefType e1, RefType e2 | e1 = erase(t1) and e2 = erase(t2) |
-    erasedHaveIntersection(e1, e2)
+    erasedHaveIntersectionFilter(e1, e2)
   )
 }
 
+bindingset[t1, t2]
+pragma[inline_late]
+private predicate erasedHaveIntersectionFilter(RefType t1, RefType t2) {
+  erasedHaveIntersection(t1, t2)
+}
+
 /**
  * Holds if there is no common (reflexive, transitive) subtype of the erasures
  * of types `t1` and `t2`.