Illuminate\Database\Eloquent\Relations\BelongsTo::getRelationQuery PHP Метод

    public function getRelationQuery(Builder $query, Builder $parent, $columns = ['*'])
    {
        if ($parent->getQuery()->from == $query->getQuery()->from) {
            return $this->getRelationQueryForSelfRelation($query, $parent, $columns);
        }
        $query->select($columns);
        $otherKey = $this->wrap($query->getModel()->getTable() . '.' . $this->otherKey);
        return $query->where($this->getQualifiedForeignKey(), '=', new Expression($otherKey));
    }