diff --git a/application/Espo/ORM/Repository/Deprecation/RDBRepositoryDeprecationTrait.php b/application/Espo/ORM/Repository/Deprecation/RDBRepositoryDeprecationTrait.php
new file mode 100644
index 0000000000..e8af245e5e
--- /dev/null
+++ b/application/Espo/ORM/Repository/Deprecation/RDBRepositoryDeprecationTrait.php
@@ -0,0 +1,517 @@
+<?php
+/************************************************************************
+ * This file is part of EspoCRM.
+ *
+ * EspoCRM - Open Source CRM application.
+ * Copyright (C) 2014-2023 Yurii Kuznietsov, Taras Machyshyn, Oleksii Avramenko
+ * Website: https://www.espocrm.com
+ *
+ * EspoCRM is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * EspoCRM is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with EspoCRM. If not, see http://www.gnu.org/licenses/.
+ *
+ * The interactive user interfaces in modified source and object code versions
+ * of this program must display Appropriate Legal Notices, as required under
+ * Section 5 of the GNU General Public License version 3.
+ *
+ * In accordance with Section 7(b) of the GNU General Public License version 3,
+ * these Appropriate Legal Notices must retain the display of the "EspoCRM" word.
+ ************************************************************************/
+
+namespace Espo\ORM\Repository\Deprecation;
+
+use Espo\ORM\Collection;
+use Espo\ORM\Entity;
+use Espo\ORM\EntityManager;
+use Espo\ORM\Mapper\BaseMapper;
+use Espo\ORM\Query\Part\Expression;
+use Espo\ORM\Query\Select;
+use Espo\ORM\Repository\RDBSelectBuilder;
+use Espo\ORM\SthCollection;
+
+/**
+ * @internal
+ * @template TEntity of Entity
+ */
+trait RDBRepositoryDeprecationTrait
+{
+    /**
+     * @deprecated Use `group` method.
+     * @param Expression|Expression[]|string|string[] $groupBy
+     * @return RDBSelectBuilder<TEntity>
+     */
+    public function groupBy($groupBy): RDBSelectBuilder
+    {
+        return $this->group($groupBy);
+    }
+
+    /**
+     * @deprecated As of v7.0. Use the Query Builder instead. Otherwise, code will be not portable.
+     */
+    protected function getPDO(): \PDO
+    {
+        return $this->entityManager->getPDO();
+    }
+
+    /**
+     * @deprecated Use `$this->entityManager`.
+     */
+    protected function getEntityManager(): EntityManager
+    {
+        return $this->entityManager;
+    }
+
+    /**
+     * @deprecated Use QueryBuilder instead.
+     * @todo Rewrite usages.
+     */
+    public function deleteFromDb(string $id, bool $onlyDeleted = false): void
+    {
+        $mapper = $this->getMapper();
+
+        if (!$mapper instanceof BaseMapper) {
+            throw new \RuntimeException("Not supported 'deleteFromDb'.");
+        }
+
+        $mapper->deleteFromDb($this->entityType, $id, $onlyDeleted);
+    }
+
+    /**
+     * Get an entity. If ID is NULL, a new entity is returned.
+     *
+     * @deprecated Use `getById` and `getNew`.
+     */
+    public function get(?string $id = null): ?Entity
+    {
+        if (is_null($id)) {
+            return $this->getNew();
+        }
+
+        return $this->getById($id);
+    }
+
+    /**
+     * @deprecated As of v6.0. Use `getRelation(...)->find()`.
+     * @param ?array<string,mixed> $params
+     * @return Collection<TEntity>|TEntity|null
+     */
+    public function findRelated(Entity $entity, string $relationName, ?array $params = null)
+    {
+        $params = $params ?? [];
+
+        if ($entity->getEntityType() !== $this->entityType) {
+            throw new \RuntimeException("Not supported entity type.");
+        }
+
+        if (!$entity->hasId()) {
+            return null;
+        }
+
+        $type = $entity->getRelationType($relationName);
+        /** @phpstan-ignore-next-line */
+        $entityType = $entity->getRelationParam($relationName, 'entity');
+
+        $additionalColumns = $params['additionalColumns'] ?? [];
+        unset($params['additionalColumns']);
+
+        $additionalColumnsConditions = $params['additionalColumnsConditions'] ?? [];
+        unset($params['additionalColumnsConditions']);
+
+        $select = null;
+
+        if ($entityType) {
+            $params['from'] = $entityType;
+            $select = Select::fromRaw($params);
+        }
+
+        if ($type === Entity::MANY_MANY && count($additionalColumns)) {
+            if ($select === null) {
+                throw new \RuntimeException();
+            }
+
+            $select = $this->applyRelationAdditionalColumns($entity, $relationName, $additionalColumns, $select);
+        }
+
+        // @todo Get rid of 'additionalColumnsConditions' usage. Use 'whereClause' instead.
+        if ($type === Entity::MANY_MANY && count($additionalColumnsConditions)) {
+            if ($select === null) {
+                throw new \RuntimeException();
+            }
+
+            $select = $this->applyRelationAdditionalColumnsConditions(
+                $entity,
+                $relationName,
+                $additionalColumnsConditions,
+                $select
+            );
+        }
+
+        /** @var Collection<TEntity>|TEntity|null $result */
+        $result = $this->getMapper()->selectRelated($entity, $relationName, $select);
+
+        if ($result instanceof SthCollection) {
+            /** @var SthCollection<TEntity> */
+            return $this->entityManager->getCollectionFactory()->createFromSthCollection($result);
+        }
+
+        return $result;
+    }
+
+    /**
+     * @deprecated As of v6.0. Use `getRelation(...)->count()`.
+     * @param ?array<string, mixed> $params
+     */
+    public function countRelated(Entity $entity, string $relationName, ?array $params = null): int
+    {
+        $params = $params ?? [];
+
+        if ($entity->getEntityType() !== $this->entityType) {
+            throw new \RuntimeException("Not supported entity type.");
+        }
+
+        if (!$entity->hasId()) {
+            return 0;
+        }
+
+        $type = $entity->getRelationType($relationName);
+        /** @phpstan-ignore-next-line */
+        $entityType = $entity->getRelationParam($relationName, 'entity');
+
+        $additionalColumnsConditions = $params['additionalColumnsConditions'] ?? [];
+        unset($params['additionalColumnsConditions']);
+
+        $select = null;
+
+        if ($entityType) {
+            $params['from'] = $entityType;
+
+            $select = Select::fromRaw($params);
+        }
+
+        if ($type === Entity::MANY_MANY && count($additionalColumnsConditions)) {
+            if ($select === null) {
+                throw new \RuntimeException();
+            }
+
+            $select = $this->applyRelationAdditionalColumnsConditions(
+                $entity,
+                $relationName,
+                $additionalColumnsConditions,
+                $select
+            );
+        }
+
+        return (int) $this->getMapper()->countRelated($entity, $relationName, $select);
+    }
+
+    /**
+     * @param string[] $columns
+     */
+    private function applyRelationAdditionalColumns(
+        Entity $entity,
+        string $relationName,
+        array $columns,
+        Select $select
+    ): Select {
+
+        if (empty($columns)) {
+            return $select;
+        }
+
+        /** @phpstan-ignore-next-line */
+        $middleName = lcfirst($entity->getRelationParam($relationName, 'relationName'));
+
+        $selectItemList = $select->getSelect();
+
+        if ($selectItemList === []) {
+            $selectItemList[] = '*';
+        }
+
+        foreach ($columns as $column => $alias) {
+            $selectItemList[] = [
+                $middleName . '.' . $column,
+                $alias
+            ];
+        }
+
+        return $this->entityManager
+            ->getQueryBuilder()
+            ->select()
+            ->clone($select)
+            ->select($selectItemList)
+            ->build();
+    }
+
+    /**
+     * @param array<string, mixed> $conditions
+     */
+    private function applyRelationAdditionalColumnsConditions(
+        Entity $entity,
+        string $relationName,
+        array $conditions,
+        Select $select
+    ): Select {
+
+        if (empty($conditions)) {
+            return $select;
+        }
+
+        /** @phpstan-ignore-next-line */
+        $middleName = lcfirst($entity->getRelationParam($relationName, 'relationName'));
+
+        $builder = $this->entityManager
+            ->getQueryBuilder()
+            ->select()
+            ->clone($select);
+
+        foreach ($conditions as $column => $value) {
+            $builder->where(
+                $middleName . '.' . $column,
+                $value
+            );
+        }
+
+        return $builder->build();
+    }
+    /**
+     * @deprecated As of v6.0. Use `getRelation(...)->isRelated(...)`.
+     * @param TEntity|string $foreign
+     */
+    public function isRelated(Entity $entity, string $relationName, $foreign): bool
+    {
+        if (!$entity->hasId()) {
+            return false;
+        }
+
+        if ($entity->getEntityType() !== $this->entityType) {
+            throw new \RuntimeException("Not supported entity type.");
+        }
+
+        /** @var mixed $foreign */
+
+        if ($foreign instanceof Entity) {
+            if (!$foreign->hasId()) {
+                return false;
+            }
+
+            $id = $foreign->getId();
+        }
+        else if (is_string($foreign)) {
+            $id = $foreign;
+        }
+        else {
+            throw new \RuntimeException("Bad 'foreign' value.");
+        }
+
+        if (!$id) {
+            return false;
+        }
+
+        if (in_array($entity->getRelationType($relationName), [Entity::BELONGS_TO, Entity::BELONGS_TO_PARENT])) {
+            if (!$entity->has($relationName . 'Id')) {
+                $entity = $this->getById($entity->getId());
+            }
+        }
+
+        /** @phpstan-var TEntity $entity */
+
+        $relation = $this->getRelation($entity, $relationName);
+
+        if ($foreign instanceof Entity) {
+            return $relation->isRelated($foreign);
+        }
+
+        return (bool) $this->countRelated($entity, $relationName, [
+            'whereClause' => [
+                'id' => $id,
+            ],
+        ]);
+    }
+    /**
+     * @deprecated As of v6.0. Use `getRelation(...)->relate(...)`.
+     * @phpstan-ignore-next-line
+     */
+    public function relate(Entity $entity, string $relationName, $foreign, $columnData = null, array $options = [])
+    {
+        if (!$entity->hasId()) {
+            throw new \RuntimeException("Can't relate an entity w/o ID.");
+        }
+
+        if (!$foreign instanceof Entity && !is_string($foreign)) {
+            throw new \RuntimeException("Bad 'foreign' value.");
+        }
+
+        if ($entity->getEntityType() !== $this->entityType) {
+            throw new \RuntimeException("Not supported entity type.");
+        }
+
+        $this->beforeRelate($entity, $relationName, $foreign, $columnData, $options);
+
+        $beforeMethodName = 'beforeRelate' . ucfirst($relationName);
+
+        if (method_exists($this, $beforeMethodName)) {
+            $this->$beforeMethodName($entity, $foreign, $columnData, $options);
+        }
+
+        $result = false;
+
+        $methodName = 'relate' . ucfirst($relationName);
+
+        if (method_exists($this, $methodName)) {
+            $result = $this->$methodName($entity, $foreign, $columnData, $options);
+        }
+        else {
+            $data = $columnData;
+
+            if ($columnData instanceof \stdClass) {
+                $data = get_object_vars($columnData);
+            }
+
+            if ($foreign instanceof Entity) {
+                $result = $this->getMapper()->relate($entity, $relationName, $foreign, $data);
+            }
+            else {
+                $id = $foreign;
+
+                $result = $this->getMapper()->relateById($entity, $relationName, $id, $data);
+            }
+        }
+
+        if ($result) {
+            $this->afterRelate($entity, $relationName, $foreign, $columnData, $options);
+
+            $afterMethodName = 'afterRelate' . ucfirst($relationName);
+
+            if (method_exists($this, $afterMethodName)) {
+                $this->$afterMethodName($entity, $foreign, $columnData, $options);
+            }
+        }
+
+        return $result;
+    }
+
+    /**
+     * @deprecated As of v6.0. Use `getRelation(...)->unrelate(...)`.
+     * @phpstan-ignore-next-line
+     */
+    public function unrelate(Entity $entity, string $relationName, $foreign, array $options = [])
+    {
+        if (!$entity->hasId()) {
+            throw new \RuntimeException("Can't unrelate an entity w/o ID.");
+        }
+
+        if (!$foreign instanceof Entity && !is_string($foreign)) {
+            throw new \RuntimeException("Bad foreign value.");
+        }
+
+        if ($entity->getEntityType() !== $this->entityType) {
+            throw new \RuntimeException("Not supported entity type.");
+        }
+
+        $this->beforeUnrelate($entity, $relationName, $foreign, $options);
+
+        $beforeMethodName = 'beforeUnrelate' . ucfirst($relationName);
+
+        if (method_exists($this, $beforeMethodName)) {
+            $this->$beforeMethodName($entity, $foreign, $options);
+        }
+
+        $result = false;
+
+        $methodName = 'unrelate' . ucfirst($relationName);
+
+        if (method_exists($this, $methodName)) {
+            $this->$methodName($entity, $foreign);
+        }
+        else {
+            if ($foreign instanceof Entity) {
+                $this->getMapper()->unrelate($entity, $relationName, $foreign);
+            }
+            else {
+                $id = $foreign;
+
+                $this->getMapper()->unrelateById($entity, $relationName, $id);
+            }
+        }
+
+        $this->afterUnrelate($entity, $relationName, $foreign, $options);
+
+        $afterMethodName = 'afterUnrelate' . ucfirst($relationName);
+
+        if (method_exists($this, $afterMethodName)) {
+            $this->$afterMethodName($entity, $foreign, $options);
+        }
+
+        return $result;
+    }
+
+    /**
+     * @deprecated As of v6.0. Use `getRelation(...)->getColumn(...)`.
+     * @phpstan-ignore-next-line
+     */
+    public function getRelationColumn(Entity $entity, string $relationName, string $foreignId, string $column)
+    {
+        return $this->getMapper()->getRelationColumn($entity, $relationName, $foreignId, $column);
+    }
+
+    /**
+     * @deprecated As of v6.0. Use `getRelation(...)->updateColumns(...)`.
+     * @phpstan-ignore-next-line
+     */
+    public function updateRelation(Entity $entity, string $relationName, $foreign, $columnData)
+    {
+        if (!$entity->hasId()) {
+            throw new \RuntimeException("Can't update a relation for an entity w/o ID.");
+        }
+
+        if (!$foreign instanceof Entity && !is_string($foreign)) {
+            throw new \RuntimeException("Bad foreign value.");
+        }
+
+        if ($columnData instanceof \stdClass) {
+            $columnData = get_object_vars($columnData);
+        }
+
+        if ($foreign instanceof Entity) {
+            $id = $foreign->getId();
+        } else {
+            $id = $foreign;
+        }
+
+        if (!is_string($id)) {
+            throw new \RuntimeException("Bad foreign value.");
+        }
+
+        $this->getMapper()->updateRelationColumns($entity, $relationName, $id, $columnData);
+
+        return true;
+    }
+
+    /**
+     * @deprecated As of v6.0. Use `getRelation(...)->massRelate(...)`.
+     * @phpstan-ignore-next-line
+     */
+    public function massRelate(Entity $entity, string $relationName, array $params = [], array $options = [])
+    {
+        if (!$entity->hasId()) {
+            throw new \RuntimeException("Can't related an entity w/o ID.");
+        }
+
+        $this->beforeMassRelate($entity, $relationName, $params, $options);
+
+        $select = Select::fromRaw($params);
+
+        $this->getMapper()->massRelate($entity, $relationName, $select);
+
+        $this->afterMassRelate($entity, $relationName, $params, $options);
+    }
+}
diff --git a/application/Espo/ORM/Repository/RDBRepository.php b/application/Espo/ORM/Repository/RDBRepository.php
index 53cfec7f8a..b6d8fa097a 100644
--- a/application/Espo/ORM/Repository/RDBRepository.php
+++ b/application/Espo/ORM/Repository/RDBRepository.php
@@ -32,6 +32,7 @@ namespace Espo\ORM\Repository;
 use Espo\ORM\EntityManager;
 use Espo\ORM\EntityFactory;
 use Espo\ORM\Collection;
+use Espo\ORM\Repository\Deprecation\RDBRepositoryDeprecationTrait;
 use Espo\ORM\Repository\Option\SaveOption;
 use Espo\ORM\SthCollection;
 use Espo\ORM\BaseEntity;
@@ -45,9 +46,7 @@ use Espo\ORM\Query\Part\Expression;
 use Espo\ORM\Query\Part\Order;
 use Espo\ORM\Mapper\BaseMapper;
 
-use stdClass;
 use RuntimeException;
-use PDO;
 
 /**
  * A relation database repository.
@@ -57,6 +56,9 @@ use PDO;
  */
 class RDBRepository implements Repository
 {
+    /** @phpstan-use RDBRepositoryDeprecationTrait<TEntity> */
+    use RDBRepositoryDeprecationTrait;
+
     protected HookMediator $hookMediator;
     protected RDBTransactionManager $transactionManager;
 
@@ -114,22 +116,6 @@ class RDBRepository implements Repository
         return $entity;
     }
 
-    /**
-     * Get an entity. If ID is NULL, a new entity is returned.
-     *
-     * @return ?TEntity
-     *
-     * @deprecated Use `getById` and `getNew`.
-     */
-    public function get(?string $id = null): ?Entity
-    {
-        if (is_null($id)) {
-            return $this->getNew();
-        }
-
-        return $this->getById($id);
-    }
-
     protected function processCheckEntity(Entity $entity): void
     {
         if ($entity->getEntityType() !== $this->entityType) {
@@ -230,20 +216,6 @@ class RDBRepository implements Repository
         $this->afterRemove($entity, $options);
     }
 
-    /**
-     * @deprecated Use QueryBuilder instead.
-     */
-    public function deleteFromDb(string $id, bool $onlyDeleted = false): void
-    {
-        $mapper = $this->getMapper();
-
-        if (!$mapper instanceof BaseMapper) {
-            throw new RuntimeException("Not supported 'deleteFromDb'.");
-        }
-
-        $mapper->deleteFromDb($this->entityType, $id, $onlyDeleted);
-    }
-
     /**
      * Find records.
      *
@@ -258,7 +230,7 @@ class RDBRepository implements Repository
     /**
      * Find one record.
      *
-     * @param ?array<string,mixed> $params @deprecated As of v6.0. Use query building.
+     * @param ?array<string, mixed> $params @deprecated As of v6.0. Use query building.
      */
     public function findOne(?array $params = []): ?Entity
     {
@@ -289,473 +261,7 @@ class RDBRepository implements Repository
     }
 
     /**
-     * @deprecated As of v6.0. Use `getRelation(...)->find()`.
-     * @param ?array<string,mixed> $params
-     * @return Collection<TEntity>|TEntity|null
-     */
-    public function findRelated(Entity $entity, string $relationName, ?array $params = null)
-    {
-        $params = $params ?? [];
-
-        if ($entity->getEntityType() !== $this->entityType) {
-            throw new RuntimeException("Not supported entity type.");
-        }
-
-        if (!$entity->hasId()) {
-            return null;
-        }
-
-        $type = $entity->getRelationType($relationName);
-        /** @phpstan-ignore-next-line */
-        $entityType = $entity->getRelationParam($relationName, 'entity');
-
-        $additionalColumns = $params['additionalColumns'] ?? [];
-        unset($params['additionalColumns']);
-
-        $additionalColumnsConditions = $params['additionalColumnsConditions'] ?? [];
-        unset($params['additionalColumnsConditions']);
-
-        $select = null;
-
-        if ($entityType) {
-            $params['from'] = $entityType;
-            $select = Select::fromRaw($params);
-        }
-
-        if ($type === Entity::MANY_MANY && count($additionalColumns)) {
-            if ($select === null) {
-                throw new RuntimeException();
-            }
-
-            $select = $this->applyRelationAdditionalColumns($entity, $relationName, $additionalColumns, $select);
-        }
-
-        // @todo Get rid of 'additionalColumnsConditions' usage. Use 'whereClause' instead.
-        if ($type === Entity::MANY_MANY && count($additionalColumnsConditions)) {
-            if ($select === null) {
-                throw new RuntimeException();
-            }
-
-            $select = $this->applyRelationAdditionalColumnsConditions(
-                $entity,
-                $relationName,
-                $additionalColumnsConditions,
-                $select
-            );
-        }
-
-        /** @var Collection<TEntity>|TEntity|null $result */
-        $result = $this->getMapper()->selectRelated($entity, $relationName, $select);
-
-        if ($result instanceof SthCollection) {
-            /** @var SthCollection<TEntity> */
-            return $this->entityManager->getCollectionFactory()->createFromSthCollection($result);
-        }
-
-        return $result;
-    }
-
-    /**
-     * @deprecated As of v6.0. Use `getRelation(...)->count()`.
-     * @param ?array<string,mixed> $params
-     */
-    public function countRelated(Entity $entity, string $relationName, ?array $params = null): int
-    {
-        $params = $params ?? [];
-
-        if ($entity->getEntityType() !== $this->entityType) {
-            throw new RuntimeException("Not supported entity type.");
-        }
-
-        if (!$entity->hasId()) {
-            return 0;
-        }
-
-        $type = $entity->getRelationType($relationName);
-        /** @phpstan-ignore-next-line */
-        $entityType = $entity->getRelationParam($relationName, 'entity');
-
-        $additionalColumnsConditions = $params['additionalColumnsConditions'] ?? [];
-        unset($params['additionalColumnsConditions']);
-
-        $select = null;
-
-        if ($entityType) {
-            $params['from'] = $entityType;
-
-            $select = Select::fromRaw($params);
-        }
-
-        if ($type === Entity::MANY_MANY && count($additionalColumnsConditions)) {
-            if ($select === null) {
-                throw new RuntimeException();
-            }
-
-            $select = $this->applyRelationAdditionalColumnsConditions(
-                $entity,
-                $relationName,
-                $additionalColumnsConditions,
-                $select
-            );
-        }
-
-        return (int) $this->getMapper()->countRelated($entity, $relationName, $select);
-    }
-
-    /**
-     * @param string[] $columns
-     */
-    protected function applyRelationAdditionalColumns(
-        Entity $entity,
-        string $relationName,
-        array $columns,
-        Select $select
-    ): Select {
-
-        if (empty($columns)) {
-            return $select;
-        }
-
-        /** @phpstan-ignore-next-line */
-        $middleName = lcfirst($entity->getRelationParam($relationName, 'relationName'));
-
-        $selectItemList = $select->getSelect();
-
-        if ($selectItemList === []) {
-            $selectItemList[] = '*';
-        }
-
-        foreach ($columns as $column => $alias) {
-            $selectItemList[] = [
-                $middleName . '.' . $column,
-                $alias
-            ];
-        }
-
-        return $this->entityManager
-            ->getQueryBuilder()
-            ->select()
-            ->clone($select)
-            ->select($selectItemList)
-            ->build();
-    }
-
-    /**
-     * @param array<string,mixed> $conditions
-     */
-    protected function applyRelationAdditionalColumnsConditions(
-        Entity $entity,
-        string $relationName,
-        array $conditions,
-        Select $select
-    ): Select {
-
-        if (empty($conditions)) {
-            return $select;
-        }
-
-        /** @phpstan-ignore-next-line */
-        $middleName = lcfirst($entity->getRelationParam($relationName, 'relationName'));
-
-        $builder = $this->entityManager
-            ->getQueryBuilder()
-            ->select()
-            ->clone($select);
-
-        foreach ($conditions as $column => $value) {
-            $builder->where(
-                $middleName . '.' . $column,
-                $value
-            );
-        }
-
-        return $builder->build();
-    }
-
-    /**
-     * @deprecated As of v6.0. Use `getRelation(...)->isRelated(...)`.
-     * @param TEntity|string $foreign
-     */
-    public function isRelated(Entity $entity, string $relationName, $foreign): bool
-    {
-        if (!$entity->hasId()) {
-            return false;
-        }
-
-        if ($entity->getEntityType() !== $this->entityType) {
-            throw new RuntimeException("Not supported entity type.");
-        }
-
-        /** @var mixed $foreign */
-
-        if ($foreign instanceof Entity) {
-            if (!$foreign->hasId()) {
-                return false;
-            }
-
-            $id = $foreign->getId();
-        }
-        else if (is_string($foreign)) {
-            $id = $foreign;
-        }
-        else {
-            throw new RuntimeException("Bad 'foreign' value.");
-        }
-
-        if (!$id) {
-            return false;
-        }
-
-        if (in_array($entity->getRelationType($relationName), [Entity::BELONGS_TO, Entity::BELONGS_TO_PARENT])) {
-            if (!$entity->has($relationName . 'Id')) {
-                $entity = $this->getById($entity->getId());
-            }
-        }
-
-        /** @phpstan-var TEntity $entity */
-
-        $relation = $this->getRelation($entity, $relationName);
-
-        if ($foreign instanceof Entity) {
-            return $relation->isRelated($foreign);
-        }
-
-        return (bool) $this->countRelated($entity, $relationName, [
-            'whereClause' => [
-                'id' => $id,
-            ],
-        ]);
-    }
-
-    /**
-     * @deprecated As of v6.0. Use `getRelation(...)->relate(...)`.
-     * @phpstan-ignore-next-line
-     */
-    public function relate(Entity $entity, string $relationName, $foreign, $columnData = null, array $options = [])
-    {
-        if (!$entity->hasId()) {
-            throw new RuntimeException("Can't relate an entity w/o ID.");
-        }
-
-        if (!$foreign instanceof Entity && !is_string($foreign)) {
-            throw new RuntimeException("Bad 'foreign' value.");
-        }
-
-        if ($entity->getEntityType() !== $this->entityType) {
-            throw new RuntimeException("Not supported entity type.");
-        }
-
-        $this->beforeRelate($entity, $relationName, $foreign, $columnData, $options);
-
-        $beforeMethodName = 'beforeRelate' . ucfirst($relationName);
-
-        if (method_exists($this, $beforeMethodName)) {
-            $this->$beforeMethodName($entity, $foreign, $columnData, $options);
-        }
-
-        $result = false;
-
-        $methodName = 'relate' . ucfirst($relationName);
-
-        if (method_exists($this, $methodName)) {
-            $result = $this->$methodName($entity, $foreign, $columnData, $options);
-        }
-        else {
-            $data = $columnData;
-
-            if ($columnData instanceof stdClass) {
-                $data = get_object_vars($columnData);
-            }
-
-            if ($foreign instanceof Entity) {
-                $result = $this->getMapper()->relate($entity, $relationName, $foreign, $data);
-            }
-            else {
-                $id = $foreign;
-
-                $result = $this->getMapper()->relateById($entity, $relationName, $id, $data);
-            }
-        }
-
-        if ($result) {
-            $this->afterRelate($entity, $relationName, $foreign, $columnData, $options);
-
-            $afterMethodName = 'afterRelate' . ucfirst($relationName);
-
-            if (method_exists($this, $afterMethodName)) {
-                $this->$afterMethodName($entity, $foreign, $columnData, $options);
-            }
-        }
-
-        return $result;
-    }
-
-    /**
-     * @deprecated As of v6.0. Use `getRelation(...)->unrelate(...)`.
-     * @phpstan-ignore-next-line
-     */
-    public function unrelate(Entity $entity, string $relationName, $foreign, array $options = [])
-    {
-        if (!$entity->hasId()) {
-            throw new RuntimeException("Can't unrelate an entity w/o ID.");
-        }
-
-        if (!$foreign instanceof Entity && !is_string($foreign)) {
-            throw new RuntimeException("Bad foreign value.");
-        }
-
-        if ($entity->getEntityType() !== $this->entityType) {
-            throw new RuntimeException("Not supported entity type.");
-        }
-
-        $this->beforeUnrelate($entity, $relationName, $foreign, $options);
-
-        $beforeMethodName = 'beforeUnrelate' . ucfirst($relationName);
-
-        if (method_exists($this, $beforeMethodName)) {
-            $this->$beforeMethodName($entity, $foreign, $options);
-        }
-
-        $result = false;
-
-        $methodName = 'unrelate' . ucfirst($relationName);
-
-        if (method_exists($this, $methodName)) {
-            $this->$methodName($entity, $foreign);
-        }
-        else {
-            if ($foreign instanceof Entity) {
-                $this->getMapper()->unrelate($entity, $relationName, $foreign);
-            }
-            else {
-                $id = $foreign;
-
-                $this->getMapper()->unrelateById($entity, $relationName, $id);
-            }
-        }
-
-        $this->afterUnrelate($entity, $relationName, $foreign, $options);
-
-        $afterMethodName = 'afterUnrelate' . ucfirst($relationName);
-
-        if (method_exists($this, $afterMethodName)) {
-            $this->$afterMethodName($entity, $foreign, $options);
-        }
-
-        return $result;
-    }
-
-    /**
-     * @deprecated As of v6.0. Use `getRelation(...)->getColumn(...)`.
-     * @phpstan-ignore-next-line
-     */
-    public function getRelationColumn(Entity $entity, string $relationName, string $foreignId, string $column)
-    {
-        return $this->getMapper()->getRelationColumn($entity, $relationName, $foreignId, $column);
-    }
-
-    /**
-     * @deprecated As of v6.0.
-     * @phpstan-ignore-next-line
-     */
-    protected function beforeRelate(Entity $entity, $relationName, $foreign, $data = null, array $options = [])
-    {
-    }
-
-    /**
-     * @deprecated As of v6.0.
-     * @phpstan-ignore-next-line
-     */
-    protected function afterRelate(Entity $entity, $relationName, $foreign, $data = null, array $options = [])
-    {
-    }
-
-    /**
-     * @deprecated As of v6.0.
-     * @phpstan-ignore-next-line
-     */
-    protected function beforeUnrelate(Entity $entity, $relationName, $foreign, array $options = [])
-    {
-    }
-
-    /**
-     * @deprecated As of v6.0.
-     * @phpstan-ignore-next-line
-     */
-    protected function afterUnrelate(Entity $entity, $relationName, $foreign, array $options = [])
-    {
-    }
-
-    /**
-     * @deprecated As of v6.0.
-     * @phpstan-ignore-next-line
-     */
-    protected function beforeMassRelate(Entity $entity, $relationName, array $params = [], array $options = [])
-    {
-    }
-
-    /**
-     * @deprecated As of v6.0.
-     * @phpstan-ignore-next-line
-     */
-    protected function afterMassRelate(Entity $entity, $relationName, array $params = [], array $options = [])
-    {
-    }
-
-    /**
-     * @deprecated As of v6.0. Use `getRelation(...)->updateColumns(...)`.
-     * @phpstan-ignore-next-line
-     */
-    public function updateRelation(Entity $entity, string $relationName, $foreign, $columnData)
-    {
-        if (!$entity->hasId()) {
-            throw new RuntimeException("Can't update a relation for an entity w/o ID.");
-        }
-
-        if (!$foreign instanceof Entity && !is_string($foreign)) {
-            throw new RuntimeException("Bad foreign value.");
-        }
-
-        if ($columnData instanceof stdClass) {
-            $columnData = get_object_vars($columnData);
-        }
-
-        if ($foreign instanceof Entity) {
-            $id = $foreign->getId();
-        } else {
-            $id = $foreign;
-        }
-
-        if (!is_string($id)) {
-            throw new RuntimeException("Bad foreign value.");
-        }
-
-        $this->getMapper()->updateRelationColumns($entity, $relationName, $id, $columnData);
-
-        return true;
-    }
-
-    /**
-     * @deprecated As of v6.0. Use `getRelation(...)->massRelate(...)`.
-     * @phpstan-ignore-next-line
-     */
-    public function massRelate(Entity $entity, string $relationName, array $params = [], array $options = [])
-    {
-        if (!$entity->hasId()) {
-            throw new RuntimeException("Can't related an entity w/o ID.");
-        }
-
-        $this->beforeMassRelate($entity, $relationName, $params, $options);
-
-        $select = Select::fromRaw($params);
-
-        $this->getMapper()->massRelate($entity, $relationName, $select);
-
-        $this->afterMassRelate($entity, $relationName, $params, $options);
-    }
-
-    /**
-     * @param array<string,mixed> $params @deprecated Use query building.
+     * @param array<string, mixed> $params @deprecated Use query building.
      */
     public function count(array $params = []): int
     {
@@ -968,24 +474,6 @@ class RDBRepository implements Repository
         return $this->createSelectBuilder()->group($groupBy);
     }
 
-    /**
-     * @deprecated Use `group` method.
-     * @param Expression|Expression[]|string|string[] $groupBy
-     * @return RDBSelectBuilder<TEntity>
-     */
-    public function groupBy($groupBy): RDBSelectBuilder
-    {
-        return $this->group($groupBy);
-    }
-
-    /**
-     * @deprecated As of v7.0. Use the Query Builder instead. Otherwise, code will be not portable.
-     */
-    protected function getPDO(): PDO
-    {
-        return $this->entityManager->getPDO();
-    }
-
     /**
      * Create a select builder.
      *
@@ -1000,7 +488,8 @@ class RDBRepository implements Repository
     }
 
     /**
-     * @param array<string,mixed> $options
+     * Use hooks instead.
+     * @param array<string, mixed> $options
      * @return void
      */
     protected function beforeSave(Entity $entity, array $options = [])
@@ -1009,7 +498,8 @@ class RDBRepository implements Repository
     }
 
     /**
-     * @param array<string,mixed> $options
+     * Use hooks instead.
+     * @param array<string, mixed> $options
      * @return void
      */
     protected function afterSave(Entity $entity, array $options = [])
@@ -1018,7 +508,8 @@ class RDBRepository implements Repository
     }
 
     /**
-     * @param array<string,mixed> $options
+     * Use hooks instead.
+     * @param array<string, mixed> $options
      * @return void
      */
     protected function beforeRemove(Entity $entity, array $options = [])
@@ -1027,7 +518,8 @@ class RDBRepository implements Repository
     }
 
     /**
-     * @param array<string,mixed> $options
+     * Use hooks instead.
+     * @param array<string, mixed> $options
      * @return void
      */
     protected function afterRemove(Entity $entity, array $options = [])
@@ -1037,17 +529,54 @@ class RDBRepository implements Repository
 
     protected function getMapper(): RDBMapper
     {
-        /** @var RDBMapper $mapper */
         $mapper = $this->entityManager->getMapper();
 
+        if (!$mapper instanceof RDBMapper) {
+            throw new RuntimeException("Mapper is not RDB.");
+        }
+
         return $mapper;
     }
 
     /**
-     * @deprecated Use `$this->entityManager`.
+     * @deprecated As of v6.0. Use hooks instead.
+     * @phpstan-ignore-next-line
      */
-    protected function getEntityManager(): EntityManager
-    {
-        return $this->entityManager;
-    }
+    protected function beforeRelate(Entity $entity, $relationName, $foreign, $data = null, array $options = [])
+    {}
+
+    /**
+     * @deprecated As of v6.0. Use hooks instead.
+     * @phpstan-ignore-next-line
+     */
+    protected function afterRelate(Entity $entity, $relationName, $foreign, $data = null, array $options = [])
+    {}
+
+    /**
+     * @deprecated As of v6.0. Use hooks instead.
+     * @phpstan-ignore-next-line
+     */
+    protected function beforeUnrelate(Entity $entity, $relationName, $foreign, array $options = [])
+    {}
+
+    /**
+     * @deprecated As of v6.0. Use hooks instead.
+     * @phpstan-ignore-next-line
+     */
+    protected function afterUnrelate(Entity $entity, $relationName, $foreign, array $options = [])
+    {}
+
+    /**
+     * @deprecated As of v6.0. Use hooks instead.
+     * @phpstan-ignore-next-line
+     */
+    protected function beforeMassRelate(Entity $entity, $relationName, array $params = [], array $options = [])
+    {}
+
+    /**
+     * @deprecated As of v6.0. Use hooks instead.
+     * @phpstan-ignore-next-line
+     */
+    protected function afterMassRelate(Entity $entity, $relationName, array $params = [], array $options = [])
+    {}
 }