change comment and function name

src/binder/bind/bind_graph_pattern.cpp

@@ -27,9 +27,10 @@ Binder::bindGraphPattern(const std::vector<std::unique_ptr<PatternElement>>& gra
     return std::make_pair(std::move(queryGraphCollection), std::move(propertyCollection));
 }
 
-void static addUndirectedTableNames(const PatternElement& patternElement) {
-    // Neighbouring nodes connected by an undirected query need to each contain a union
-    // of table names so that the query works.
+void static rewriteNodeTableNameForUndirectedRel(const PatternElement& patternElement) {
+    // For undirected pattern (A)-[R]-(B), we need to match R in both FWD and BWD direction.
+    // Since computation always starts from one node, we need to rewrite the node table names to be
+    // the union of both node table names, i.e. (A|B)-[R]-(A|B)
     auto leftNode = patternElement.getFirstNodePattern();
     for (auto i = 0u; i < patternElement.getNumPatternElementChains(); ++i) {
         auto patternElementChain = patternElement.getPatternElementChain(i);
@@ -54,7 +55,7 @@ void static addUndirectedTableNames(const PatternElement& patternElement) {
 // Grammar ensures pattern element is always connected and thus can be bound as a query graph.
 std::unique_ptr<QueryGraph> Binder::bindPatternElement(
     const PatternElement& patternElement, PropertyKeyValCollection& collection) {
-    addUndirectedTableNames(patternElement);
+    rewriteNodeTableNameForUndirectedRel(patternElement);
     auto queryGraph = std::make_unique<QueryGraph>();
     auto leftNode = bindQueryNode(*patternElement.getFirstNodePattern(), *queryGraph, collection);
     for (auto i = 0u; i < patternElement.getNumPatternElementChains(); ++i) {