Bind Argument ops to the subplan they belong to (#2167)

Co-authored-by: Roi Lipman <swilly22@users.noreply.github.com>

src/execution_plan/execution_plan_build/execution_plan_modify.c

@@ -268,7 +268,7 @@ OpBase *ExecutionPlan_LocateReferences
 	rax *refs_to_resolve
 ) {
 	return ExecutionPlan_LocateReferencesExcludingOps(
-			root, recurse_limit, NULL, 0, refs_to_resolve);
+			   root, recurse_limit, NULL, 0, refs_to_resolve);
 }
 
 void _ExecutionPlan_LocateTaps
@@ -368,7 +368,8 @@ OpBase *ExecutionPlan_BuildOpsFromPath(ExecutionPlan *plan, const char **bound_v
 	match_stream_plan->record_map = plan->record_map;
 
 	// If we have bound variables, build an Argument op that represents them.
-	if(bound_vars) match_stream_plan->root = NewArgumentOp(plan, bound_vars);
+	if(bound_vars) match_stream_plan->root = NewArgumentOp(match_stream_plan,
+															   bound_vars);
 
 	AST *ast = QueryCtx_GetAST();
 	// Build a temporary AST holding a MATCH clause.

tests/flow/test_optional_match.py

@@ -1,5 +1,4 @@
-import os
-import sys
+import re
 from RLTest import Env
 from redisgraph import Graph, Node, Edge
 from base import FlowTestsBase
@@ -275,3 +274,20 @@ def test21_optional_filters_without_references(self):
         actual_result = redis_graph.query(query)
         expected_result = [['v1', 'v2']]
         self.env.assertEquals(actual_result.result_set, expected_result)
+
+    # validate that the correct plan is populated and executed when OPTIONAL
+    # does not introduce any new variables
+    def test22_optional_repeats_reference(self):
+        global redis_graph
+        query = """MATCH (n1) OPTIONAL MATCH (n1) WHERE n1.nonexistent > 0 RETURN n1.v ORDER BY n1.v"""
+        plan = redis_graph.execution_plan(query)
+        # the first child of the Apply op should be a scan and the
+        # second should be the OPTIONAL subtree
+        self.env.assertTrue(re.search('Apply\s+All Node Scan | (n1)\s+Optional\s+Filter\s+Argument', plan))
+
+        actual_result = redis_graph.query(query)
+        expected_result = [['v1'],
+                           ['v2'],
+                           ['v3'],
+                           ['v4']]
+        self.env.assertEquals(actual_result.result_set, expected_result)