pgcrypto和order by

Question

我想在这样的查询中对某些列进行ORDER BY：

SELECT "created", 
        pgp_pub_decrypt(username, dearmor('-----BEGIN PGP PRIVATE KEY BLOCK----- XXXXXXX -----END PGP PRIVATE KEY BLOCK-----'), 'password') AS "username" 
FROM "users" 
ORDER BY created

无论我使用什么列进行排序，都需要很长时间才能进行计算。我知道我可以将这个选项包装在另一个中并在那里进行排序，但这不能解决其他原因。为什么这么长时间？我做错了吗？

这是查询计划：

QUERY PLAN
-----------------------------------------------------------------------
 Sort  (cost=1261.92..1273.00 rows=4433 width=40)
  Sort Key: created
   ->  Seq Scan on users  (cost=0.00..993.41 rows=4433 width=40)

EXPLAIN的结果（分析，缓冲）：

QUERY PLAN
--------------------------------------------------------------------------------------------------------------------
 Sort  (cost=1261.92..1273.00 rows=4433 width=40) (actual time=313515.489..313516.446 rows=4433 loops=1)
   Sort Key: created
   Sort Method: quicksort  Memory: 531kB
   Buffers: shared hit=2037
   ->  Seq Scan on users  (cost=0.00..993.41 rows=4433 width=40) (actual time=70.300..313499.510 rows=4433 loops=1)
         Buffers: shared hit=2037
 Planning time: 0.115 ms
 Execution time: 313517.322 ms