Implement #7865: Consider the return value of deterministic functions to be invariant if all its arguments are invariant

Author: dyemanov

src/dsql/ExprNodes.cpp

@@ -13429,12 +13429,28 @@ ValueExprNode* UdfCallNode::pass1(thread_db* tdbb, CompilerScratch* csb)
 
 ValueExprNode* UdfCallNode::pass2(thread_db* tdbb, CompilerScratch* csb)
 {
-	if (function->fun_deterministic && !function->fun_inputs)
+	if (function->fun_deterministic)
 	{
 		// Deterministic function without input arguments is expected to be
-		// always returning the same result, so it can be marked as invariant
-		nodFlags |= FLAG_INVARIANT;
-		csb->csb_invariants.push(&impureOffset);
+		// always returning the same result, so it can be marked as invariant.
+		// Ditto if all its input arguments are deterministic expressions
+		// that do not reference any stream.
+
+		bool invariant = true;
+		for (const auto& arg : args->items)
+		{
+			if (!arg->deterministic() || arg->containsAnyStream())
+			{
+				invariant = false;
+				break;
+			}
+		}
+
+		if (invariant)
+		{
+			nodFlags |= FLAG_INVARIANT;
+			csb->csb_invariants.push(&impureOffset);
+		}
 	}
 
 	ValueExprNode::pass2(tdbb, csb);

src/dsql/Nodes.h

@@ -698,6 +698,14 @@ class ExprNode : public DmlNode
 		return false;
 	}
 
+	bool containsAnyStream() const
+	{
+		SortedStreamList nodeStreams;
+		collectStreams(nodeStreams);
+
+		return nodeStreams.hasData();
+	}
+
 	virtual bool dsqlMatch(DsqlCompilerScratch* dsqlScratch, const ExprNode* other, bool ignoreMapCast) const;
 
 	virtual ExprNode* dsqlPass(DsqlCompilerScratch* dsqlScratch)