Re: Avoid detoast overhead when possible

Hi,

With your setup (table created with setup.sql):
postgres(at)postgres=# explain analyze select big->'1', big->'2', big->'3',
big->'5', big->'10' from b;
QUERY PLAN
------------------------------------------------------------------------------------------------------
Seq Scan on b (cost=0.00..29.52 rows=1001 width=160) (actual
time=0.656..359.964 rows=1001 loops=1)
Planning Time: 0.042 ms
Execution Time: 360.177 ms
(3 rows)

Time: 361.054 ms
postgres(at)postgres=# explain analyze select big->'1' from b;
QUERY PLAN
----------------------------------------------------------------------------------------------------
Seq Scan on b (cost=0.00..19.51 rows=1001 width=32) (actual
time=0.170..63.996 rows=1001 loops=1)
Planning Time: 0.042 ms
Execution Time: 64.063 ms
(3 rows)

Time: 64.626 ms

Without patch, the same table and queries:
postgres(at)postgres=# explain analyze select big->'1', big->'2', big->'3',
big->'5', big->'10' from b;
QUERY PLAN
------------------------------------------------------------------------------------------------------
Seq Scan on b (cost=0.00..29.52 rows=1001 width=160) (actual
time=0.665..326.399 rows=1001 loops=1)
Planning Time: 0.035 ms
Execution Time: 326.508 ms
(3 rows)

Time: 327.132 ms
postgres(at)postgres=# explain analyze select big->'1' from b;
QUERY PLAN
----------------------------------------------------------------------------------------------------
Seq Scan on b (cost=0.00..19.51 rows=1001 width=32) (actual
time=0.159..62.807 rows=1001 loops=1)
Planning Time: 0.033 ms
Execution Time: 62.879 ms
(3 rows)

Time: 63.504 ms

--
Regards,
Nikita Malakhov
Postgres Professional
The Russian Postgres Company
https://postgrespro.ru/