diff --git a/database/rag-inference.js b/database/rag-inference.js
index 76566af..c0ce4ca 100644
--- a/database/rag-inference.js
+++ b/database/rag-inference.js
@@ -62,9 +62,11 @@ export async function loadDataset(dataset_name, dataset_url, force = false) {
  * Search in given dataset using provided embedding value to get Q/A pair
  * @param {String} dataset_name The dataset name to be query from
  * @param {Array<Float>} vector The embedding result to be searched
+ * @param {Number} max_distance If the calculated distance is over given max_distance, then the result will be excluded.  
+ * Default to `1`.
  * @returns {Promise<EmbeddingSearchResult|null>} If there's no result, returns null, otherwise returns the result
  */
-export async function searchByEmbedding(dataset_name, vector) {
+export async function searchByEmbedding(dataset_name, vector, max_distance = 1) {
     const embedding_result = (await (
         await getTable(DATASET_TABLE)
     ).search(vector).where(`dataset_name = "${dataset_name}"`)
@@ -72,6 +74,7 @@ export async function searchByEmbedding(dataset_name, vector) {
 
     if(embedding_result) {
         const { question, answer, _distance } = embedding_result;
+        if(_distance >= max_distance) return null;
         return { question, answer, _distance }
     }
     return null;
@@ -82,12 +85,14 @@ export async function searchByEmbedding(dataset_name, vector) {
  * This will firstly embedding the message and query use {@link searchByEmbedding}
  * @param {String} dataset_name The dataset name to be query from
  * @param {String} message The message to be searched
+ * @param {Number} max_distance If the calculated distance is over given max_distance, then the result will be excluded.  
+ * Default to `1`.
  * @returns {Promise<EmbeddingSearchResult|null>} If there's no result, returns null, otherwise returns the result
  */
-export async function searchByMessage(dataset_name, message) {
+export async function searchByMessage(dataset_name, message, max_distance = 1) {
     const { embedding, http_error } = await post('embedding', {body: {
         content: message
     }}, { eng: "embedding" });
 
-    return http_error ? null : await searchByEmbedding(dataset_name, embedding);
+    return http_error ? null : await searchByEmbedding(dataset_name, embedding, max_distance);
 }
\ No newline at end of file