From dd31ac55fd3eb56667ac7c9eaa75ba89bbaf66e7 Mon Sep 17 00:00:00 2001
From: Andrii Shvaika <ashvayka@thingsboard.io>
Date: Thu, 6 Aug 2020 12:58:00 +0300
Subject: [PATCH] Performance improvement for queries with no results

---
 .../server/dao/sql/query/DefaultEntityQueryRepository.java   | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/dao/src/main/java/org/thingsboard/server/dao/sql/query/DefaultEntityQueryRepository.java b/dao/src/main/java/org/thingsboard/server/dao/sql/query/DefaultEntityQueryRepository.java
index b51f6a53e0..2bb99fe75b 100644
--- a/dao/src/main/java/org/thingsboard/server/dao/sql/query/DefaultEntityQueryRepository.java
+++ b/dao/src/main/java/org/thingsboard/server/dao/sql/query/DefaultEntityQueryRepository.java
@@ -5,7 +5,7 @@
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
- *     http://www.apache.org/licenses/LICENSE-2.0
+ * http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
@@ -315,6 +315,9 @@ public class DefaultEntityQueryRepository implements EntityQueryRepository {
             String countQuery = String.format("select count(id) %s", fromClauseCount);
             int totalElements = jdbcTemplate.queryForObject(countQuery, ctx, Integer.class);
 
+            if (totalElements == 0) {
+                return new PageData<>();
+            }
             String dataQuery = String.format("select * %s", fromClauseData);
 
             EntityDataSortOrder sortOrder = pageLink.getSortOrder();