Miscellany

SELECT  
    _comment.*,  
    _article.title as article_title, 
    _article.reference as article_reference 
FROM   _comment 
JOIN _article 
    ON _comment.parent_id = _article.id 
WHERE  _comment.path <@ '0.1.635696' 
ORDER BY (localtimestamp - _comment.date_publishing) ASC
OFFSET 0 
LIMIT  5;

----

------------------
 Limit  (cost=37638.01..37638.02 rows=5 width=581) (actual time=4.381..4.426 rows=5 loops=1)
   ->  Sort  (cost=37638.01..37654.12 rows=6444 width=581) (actual time=4.371..4.385 rows=5 loops=1)
         Sort Key: (('now'::text)::timestamp without time zone - _comment.date_publishing)
         ->  Nested Loop  (cost=422.56..37230.30 rows=6444 width=581) (actual time=1.151..3.909 rows=52 loops=1)
               ->  Bitmap Heap Scan on _comment  (cost=422.56..14230.64 rows=6444 width=547) (actual time=1.007..1.360 rows=71 loops=1)
                     Recheck Cond: (path <@ '0.1.635696'::ltree)
                     ->  Bitmap Index Scan on gist_idx_comment_path  (cost=0.00..420.95 rows=6444 width=0) (actual time=0.973..0.973 rows=71 loops=1)
                           Index Cond: (path <@ '0.1.635696'::ltree)
               ->  Index Scan using _article_pkey on _article  (cost=0.00..3.55 rows=1 width=42) (actual time=0.017..0.020 rows=1 loops=71)
                     Index Cond: (_comment.parent_id = _article.id)
 Total runtime: 4.760 ms
(11 rows)