executor: support index nested loop hash join

executor/builder.go

@@ -1803,7 +1803,10 @@ func (b *executorBuilder) buildIndexLookUpJoin(v *plannercore.PhysicalIndexJoin)
 	e.innerCtx.keyCols = innerKeyCols
 	e.joinResult = newFirstChunk(e)
 	executorCounterIndexLookUpJoin.Inc()
-	return e
+	if v.KeepOuterOrder {
+		return e
+	}
+	return &IndexNestedLoopHashJoin{IndexLookUpJoin: *e}
 }
 
 // containsLimit tests if the execs contains Limit because we do not know whether `Limit` has consumed all of its' source,