relational query: Limit the max level to break the infinite loop when circles appear in relation graph

dao/src/main/java/org/thingsboard/server/dao/sql/query/DefaultEntityQueryRepository.java

@@ -223,6 +223,7 @@ public class DefaultEntityQueryRepository implements EntityQueryRepository {
     private static final String SELECT_API_USAGE_STATE = "(select aus.id, aus.created_time, aus.tenant_id, aus.entity_id, " +
             "coalesce((select title from tenant where id = aus.entity_id), (select title from customer where id = aus.entity_id)) as name " +
             "from api_usage_state as aus)";
+    static final int MAX_LEVEL_DEFAULT = 10; //This value has to be reasonable small to prevent infinite recursion as early as possible
 
     static {
         entityTableMap.put(EntityType.ASSET, "asset");
@@ -704,8 +705,12 @@ public class DefaultEntityQueryRepository implements EntityQueryRepository {
         return whereFilter.toString();
     }
 
-    private String getLvlFilter(int maxLevel) {
-        return maxLevel > 0 ? ("and lvl <= " + (maxLevel - 1)) : "";
+    String getLvlFilter(int maxLevel) {
+        return "and re.lvl <= " + (getMaxLevel(maxLevel) - 1);
+    }
+
+    int getMaxLevel(int maxLevel) {
+        return maxLevel > 0 ? maxLevel : MAX_LEVEL_DEFAULT;
     }
 
     private String getQueryTemplate(EntitySearchDirection direction) {

dao/src/test/java/org/thingsboard/server/dao/service/BaseEntityServiceTest.java

@@ -568,9 +568,9 @@ public abstract class BaseEntityServiceTest extends AbstractServiceTest {
 
         createManyCustomRelationsBetweenTwoNodes(tenantId, "UseCase", assets, devices);
         createHorizontalRingRelations(tenantId, "Ring(Loop)-Ast", assets);
-        //createLoopRelations(tenantId, "Loop-Tnt-Ast-Dev", tenantId, assets.get(0).getId(), devices.get(0).getId());
-        //createLoopRelations(tenantId, "Loop-Tnt-Ast", tenantId, assets.get(1).getId());
-        //createLoopRelations(tenantId, "Loop-Ast-Tnt-Ast", assets.get(2).getId(), tenantId, assets.get(3).getId());
+        createLoopRelations(tenantId, "Loop-Tnt-Ast-Dev", tenantId, assets.get(0).getId(), devices.get(0).getId());
+        createLoopRelations(tenantId, "Loop-Tnt-Ast", tenantId, assets.get(1).getId());
+        createLoopRelations(tenantId, "Loop-Ast-Tnt-Ast", assets.get(2).getId(), tenantId, assets.get(3).getId());
     }
 
     void createLoopRelations(TenantId tenantId, String type, EntityId... ids) {

dao/src/test/java/org/thingsboard/server/dao/sql/query/DefaultEntityQueryRepositoryTest.java

@@ -0,0 +1,42 @@
+package org.thingsboard.server.dao.sql.query;
+
+import org.junit.Test;
+import org.thingsboard.server.common.data.id.CustomerId;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.containsString;
+import static org.hamcrest.Matchers.equalTo;
+import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.BDDMockito.willCallRealMethod;
+import static org.mockito.Mockito.mock;
+
+public class DefaultEntityQueryRepositoryTest {
+
+    /*
+     * This value has to be reasonable small to prevent infinite recursion as early as possible
+     * */
+    @Test
+    public void givenDefaultMaxLevel_whenStaticConstant_thenEqualsTo() {
+        assertThat(DefaultEntityQueryRepository.MAX_LEVEL_DEFAULT, equalTo(10));
+    }
+
+    @Test
+    public void givenMaxLevelZeroOrNegative_whenGetMaxLevel_thenReturnDefaultMaxLevel() {
+        DefaultEntityQueryRepository repo = mock(DefaultEntityQueryRepository.class);
+        willCallRealMethod().given(repo).getMaxLevel(anyInt());
+        assertThat(repo.getMaxLevel(0), equalTo(DefaultEntityQueryRepository.MAX_LEVEL_DEFAULT));
+        assertThat(repo.getMaxLevel(-1), equalTo(DefaultEntityQueryRepository.MAX_LEVEL_DEFAULT));
+        assertThat(repo.getMaxLevel(-2), equalTo(DefaultEntityQueryRepository.MAX_LEVEL_DEFAULT));
+        assertThat(repo.getMaxLevel(Integer.MIN_VALUE), equalTo(DefaultEntityQueryRepository.MAX_LEVEL_DEFAULT));
+    }
+
+    @Test
+    public void givenMaxLevelPositive_whenGetMaxLevel_thenValueTheSame() {
+        DefaultEntityQueryRepository repo = mock(DefaultEntityQueryRepository.class);
+        willCallRealMethod().given(repo).getMaxLevel(anyInt());
+        assertThat(repo.getMaxLevel(1), equalTo(1));
+        assertThat(repo.getMaxLevel(2), equalTo(2));
+        assertThat(repo.getMaxLevel(Integer.MAX_VALUE), equalTo(Integer.MAX_VALUE));
+    }
+
+}