Index: src/main/java/com/db/finki/www/build_board/entity/blacklisted_user/BlacklistedUser.java
===================================================================
--- src/main/java/com/db/finki/www/build_board/entity/blacklisted_user/BlacklistedUser.java	(revision 2626dbcc27e66a04666be61151a9c4d7f5eb4249)
+++ src/main/java/com/db/finki/www/build_board/entity/blacklisted_user/BlacklistedUser.java	(revision 5cad1def03cc15d467828e6f6469d1b47224f6b0)
@@ -13,22 +13,22 @@
 @Getter
 @Setter
-@IdClass(BlacklistedUserId.class)
 public class BlacklistedUser {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.SEQUENCE,generator = "blacklisted_user_id_gen")
+    @SequenceGenerator(name = "blacklisted_user_id_gen",sequenceName = "blacklisted_user_id_seq",allocationSize=1)
+    private Integer id;
     @ManyToOne
-    @Id
     @JoinColumn(name = "topic_id")
     Topic topic;
 
     @ManyToOne
-    @Id
     @JoinColumn(name = "moderator_id")
     Moderator moderator;
 
-    @Id
     @Column(name = "start_date")
     LocalDateTime startTime;
 
     @ManyToOne
-    @Id
     @JoinColumn(name = "user_id")
     BBUser refersTo;
Index: src/main/java/com/db/finki/www/build_board/repository/BlacklistedUserRepo.java
===================================================================
--- src/main/java/com/db/finki/www/build_board/repository/BlacklistedUserRepo.java	(revision 2626dbcc27e66a04666be61151a9c4d7f5eb4249)
+++ src/main/java/com/db/finki/www/build_board/repository/BlacklistedUserRepo.java	(revision 5cad1def03cc15d467828e6f6469d1b47224f6b0)
@@ -9,4 +9,5 @@
 import org.springframework.data.repository.query.Param;
 
+import java.time.LocalDateTime;
 import java.util.List;
 
@@ -17,5 +18,5 @@
                 select *
                 from blacklisted_user bu
-                where bu.end_date is NULL and bu.user_id=:userId and bu.topic_id = :topicId 
+                where bu.end_date is NULL and bu.user_id=:userId and bu.topic_id = :topicId
         ) 
     """)
@@ -32,4 +33,4 @@
     void revoke(@Param("topic") long topicId, @Param("user") int blacklistedUserId);
 
-    List<BlacklistedUser> findAllByTopicId(Integer topicId);
+    List<BlacklistedUser> findAllByTopicIdAndEndTimeIsNull(Integer topicI);
 }
Index: src/main/java/com/db/finki/www/build_board/service/BlacklistedUserService.java
===================================================================
--- src/main/java/com/db/finki/www/build_board/service/BlacklistedUserService.java	(revision 2626dbcc27e66a04666be61151a9c4d7f5eb4249)
+++ src/main/java/com/db/finki/www/build_board/service/BlacklistedUserService.java	(revision 5cad1def03cc15d467828e6f6469d1b47224f6b0)
@@ -5,4 +5,5 @@
 import org.springframework.stereotype.Service;
 
+import java.time.LocalDateTime;
 import java.util.List;
 import java.util.Set;
@@ -24,5 +25,5 @@
 
     public Set<Integer> findForTopic(int topicId) {
-       return blacklistedUserRepo.findAllByTopicId(topicId).stream().map(b -> b.getRefersTo()
+       return blacklistedUserRepo.findAllByTopicIdAndEndTimeIsNull(topicId).stream().map(b -> b.getRefersTo()
                .getId()).collect(Collectors.toSet());
     }
Index: src/main/resources/db/migration/V1__init_ddl.sql
===================================================================
--- src/main/resources/db/migration/V1__init_ddl.sql	(revision 2626dbcc27e66a04666be61151a9c4d7f5eb4249)
+++ src/main/resources/db/migration/V1__init_ddl.sql	(revision 5cad1def03cc15d467828e6f6469d1b47224f6b0)
@@ -90,5 +90,6 @@
     title     VARCHAR(256) NOT NULL,
     id        INT PRIMARY KEY REFERENCES embeddable_thread (id) on delete cascade, --INHERITANCE
-    parent_id int REFERENCES project_thread (id) on delete CASCADE                 --PARENT
+    parent_id int REFERENCES project_thread (id) on delete CASCADE,                 --PARENT
+    UNIQUE (parent_id, title)
 );
 create table topic_guidelines
@@ -132,11 +133,12 @@
 CREATE TABLE blacklisted_user
 (
-    topic_id     INT REFERENCES topic_thread (id) ON DELETE CASCADE NOT NULL, --BLACLISTED_FROM
-    user_id      INT REFERENCES users (id) ON DELETE CASCADE NOT NULL,        --REFERS_TO
-    moderator_id INT REFERENCES moderator (id) ON DELETE CASCADE NOT NULL,    --BLACKLISTED_BY
-    start_date   TIMESTAMP NOT NULL,
+    id serial primary key,
+    topic_id     INT REFERENCES thread (id) ON DELETE CASCADE,
+    user_id      INT REFERENCES users (id) ON DELETE CASCADE,
+    moderator_id INT REFERENCES users (id) ON DELETE CASCADE,
+    start_date   TIMESTAMP,
     end_date     TIMESTAMP,
     reason       TEXT,
-    PRIMARY KEY (user_id, moderator_id, topic_id, start_date)
+    UNIQUE (user_id, moderator_id, topic_id, start_date)
 );
 CREATE TABLE developer_associated_with_project