어떤 식의 db 쿼리가 효율적인가요?

$args = new stdClass;
$args->member_srl = $this->user->member_srl;
$args->list_count = 20;
$args->page_count = 5;
$args->page = Context::get('page') ? intval(Context::get('page')): 1;

(중략)

$oDB = DB::getInstance();
$query = '
(SELECT document_voted_log.document_srl, null as comment_srl, document_voted_log.regdate as voted_date
FROM document_voted_log LEFT JOIN comment_voted_log ON document_voted_log.member_srl = comment_voted_log.member_srl
WHERE document_voted_log.member_srl = ?)
UNION
(SELECT null as document_srl, comment_voted_log.comment_srl, comment_voted_log.regdate as voted_date
FROM document_voted_log RIGHT JOIN comment_voted_log ON document_voted_log.member_srl = comment_voted_log.member_srl
WHERE comment_voted_log.member_srl = ?)
ORDER BY voted_date DESC
';
$stmt = $oDB->query($query, [$args->member_srl, $args->member_srl]);
$result = $stmt->fetchAll();

$count = count($result);
$limit = $args->list_count;
if ( $args->page > 1 )
{
    $limit = $args->list_count * ($args->page - 1);
}

$output = new stdClass;
$output->data = array();
foreach ( $result as $key => $attribute )
{
    if ( $args->page === 1 && $key >= $limit )
    {
        continue;
    }
    if ( $args->page > 1 && ($key < $limit || $key >= $limit + $args->list_count) )
    {
        continue;
    }

    if ( isset($attribute->document_srl) )
    {
        $oDocument = DocumentModel::getDocument($attribute->document_srl);
        $oDocument->variables['voted_date'] = $attribute->voted_date;
        $output->data[$count - $key] = $oDocument;
    }
    else if ( isset($attribute->comment_srl) )
    {
        $oComment = CommentModel::getComment($attribute->comment_srl);
        $oComment->variables['voted_date'] = $attribute->voted_date;
        $output->data[$count - $key] = $oComment;
    }
}

$output->total_count = $count;
$output->total_page = ceil($output->total_count / $args->list_count);
$output->page = $args->page;

$output->page_navigation = new PageHandler($output->total_count, $output->total_page, $output->page, $args->page_count);

$args = new stdClass;
$args->member_srl = $this->user->member_srl;
$args->list_count = $list_count = 20;
$args->page_count = 5;
$args->page = $page = Context::get('page') ? intval(Context::get('page')): 1;

(중략)

$document_output = executeQueryArray('voted.getTotalVotedDocuments', $args);
$comment_output = executeQueryArray('voted.getTotalVotedComments', $args);

// 글 목록과 댓글 목록을 병합하고 추천일(voted_date) 기준으로 재정렬
$result = array_merge($document_output->data, $comment_output->data);
if ( empty($result) )
{
    return;
}
usort($result, fn($a, $b) => strcmp($b->voted_date, $a->voted_date));

// 글과 댓글의 카운트와 페이지 재계산
$output = new stdClass;
$output->total_count = $total_count = count($result);
$output->total_page = $total_page = ceil($total_count / $list_count);
$output->page = $page;

// 목록의 항목들에 들어갈 객체 변수를 가져옴
$limit = $list_count;
if ( $page > 1 )
{
    $limit = $list_count * ($page - 1);
}

$output->data = array();
foreach ( $result as $key => $attribute )
{
    // 현재 페이지에 들어가지 않는 항목은 건너뜀
    if ( $page === 1 && $key >= $limit )
    {
        continue;
    }
    if ( $page > 1 && ($key < $limit || $key >= $limit + $list_count) )
    {
        continue;
    }

    // 문서 및 댓글 객체를 가져옴
    if ( isset($attribute->document_srl) )
    {
        $oDocument = DocumentModel::getDocument($attribute->document_srl);
        $oDocument->variables['voted_date'] = $attribute->voted_date;
        $output->data[$total_count - $key] = $oDocument;
    }
    else if ( isset($attribute->comment_srl) )
    {
        $oComment = CommentModel::getComment($attribute->comment_srl);
        $oComment->variables['voted_date'] = $attribute->voted_date;
        $output->data[$total_count - $key] = $oComment;
    }
}

// 페이지네비게이션 정의
$output->page_navigation = new PageHandler($output->total_count, $output->total_page, $output->page, $args->page_count);