QB: reduce number of MLv2 calls (#39208)

frontend/src/metabase/query_builder/components/notebook/steps/JoinStep/use-join-condition.ts

@@ -24,7 +24,7 @@ export function useJoinCondition(
   );
   const [operator, _setOperator] = useState<
     Lib.JoinConditionOperator | undefined
-  >(getInitialConditionOperator(query, stageIndex, condition));
+  >(getInitialConditionOperator(query, stageIndex, conditionParts));
 
   useEffect(() => {
     if (condition && previousCondition !== condition) {
@@ -180,19 +180,16 @@ function getDefaultJoinOperator(
 function getInitialConditionOperator(
   query: Lib.Query,
   stageIndex: number,
-  condition?: Lib.JoinCondition,
+  conditionParts: Lib.JoinConditionParts | undefined,
 ) {
-  if (condition) {
-    const { operator, lhsColumn, rhsColumn } = Lib.joinConditionParts(
-      query,
-      stageIndex,
-      condition,
-    );
+  if (conditionParts) {
+    const { operator, lhsColumn, rhsColumn } = conditionParts;
+
     return (
       operator ||
       getDefaultJoinOperator(query, stageIndex, lhsColumn, rhsColumn)
     );
-  } else {
-    return getDefaultJoinOperator(query, stageIndex, undefined, undefined);
   }
+
+  return getDefaultJoinOperator(query, stageIndex, undefined, undefined);
 }