Add bugfix comment

src/main/scala/datalog/execution/SemiNaiveExecutionEngine.scala

@@ -98,7 +98,8 @@ class SemiNaiveExecutionEngine(override val storageManager: StorageManager, stra
         innerSolve(toSolve, relations.toSeq)
         if (idx < strata.length - 1)
           storageManager.updateDiscovered()
-          storageManager.clearKnownDelta()
+          storageManager.clearKnownDelta()  // KnownDelta is not always empty when moving to the next stratum,
+                                            // it is a problem for aggregates because it leads to the creation of unwanted tuples.
       )
     storageManager.getNewIDBResult(toSolve)
   }

src/main/scala/datalog/execution/ir/IROp.scala

@@ -132,7 +132,7 @@ case class UpdateDiscoveredOp()(using JITOptions) extends IROp[Any] {
   val code: OpCode = OpCode.UPDATE_DISCOVERED
   override def run(storageManager: StorageManager): Any =
     storageManager.updateDiscovered()
-    storageManager.clearKnownDelta()
+    storageManager.clearKnownDelta()  // See explanation in SemiNaiveExecutionEngine::solve
 
   override def run_continuation(storageManager: StorageManager, opFns: Seq[CompiledFn[Any]]): Any =
     run(storageManager)