Selecting from pg_catalog.pg_settings got slow after updating to PostgreSQL 12 (windows)

Question

We have noticed a severe decrease in performance reading pg_catalog.pg_settings table in PostgreSQL 12 on MS Windows 10 machines compared to earlier versions.

explain (analyze, buffers, timing)
SELECT * from pg_catalog.pg_settings where name =
'standard_conforming_strings';

On PostgreSQL 12.5, compiled by Visual C++ build 1914, 64-bit:

Function Scan on pg_show_all_settings a  (cost=0.00..12.50 rows=5
width=485) (actual time=343.350..343.356 rows=1 loops=1)
  Filter: (name = 'standard_conforming_strings'::text)
  Rows Removed by Filter: 313
Planning Time: 0.079 ms
Execution Time: 343.397 ms

Compare to PostgreSQL 11.13, compiled by Visual C++ build 1914, 64-bit:

Function Scan on pg_show_all_settings a  (cost=0.00..12.50 rows=5
width=485) (actual time=0.723..0.728 rows=1 loops=1)
  Filter: (name = 'standard_conforming_strings'::text)
  Rows Removed by Filter: 289
Planning Time: 0.125 ms
Execution Time: 0.796 ms

This is standard installation, the changed parameters are:

SELECT name, current_setting(name), source
FROM pg_settings
WHERE source NOT IN ('default', 'override');

name	current_setting	source
client_encoding	UTF8	client
DateStyle	ISO, YMD	client
default_text_search_config	pg_catalog.simple	session
default_transaction_isolation	read committed	session
dynamic_shared_memory_type	windows	configuration file
extra_float_digits	3	session
lc_messages	Lithuanian_Lithuania.1257	configuration file
lc_monetary	Lithuanian_Lithuania.1257	configuration file
lc_numeric	Lithuanian_Lithuania.1257	configuration file
lc_time	Lithuanian_Lithuania.1257	configuration file
listen_addresses	*	configuration file
log_destination	stderr	configuration file
log_file_mode	0640	configuration file
log_timezone	Europe/Helsinki	configuration file
logging_collector	on	configuration file
max_connections	100	configuration file
max_stack_depth	2MB	environment variable
max_wal_size	1GB	configuration file
min_wal_size	80MB	configuration file
port	5444	configuration file
search_path	"$user", public	session
shared_buffers	128MB	configuration file
TimeZone	Europe/Helsinki	client

The slowing down is observed on MS Windows 10 machines only. We have pg12 on linux (PostgreSQL 12.6 (Debian 12.6-1.pgdg100+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 8.3.0-6) 8.3.0, 64-bit ) that doesn't show any decrease in performance.

I've tested different versions and it seems the problem appeared on PG12, earlier versions up to PG11 work ok. PG13 also suffers from low reading speed of pg_settings.

The behaviour is reproduced on 3 different machines (2 virtual and one physical, different hardware).

What is the cause of this? How to fix the issue?

I've found a similar question Select from pg_settings is very slow but it still has no answer too.

UPDATE

I've tested PostgreSQL 14 - there is a noticible performance increase. PostgreSQL 14.0, compiled by Visual C++ build 1914, 64-bit:

Function Scan on pg_show_all_settings a  (cost=0.00..12.50 rows=5 width=485) (actual time=8.502..8.508 rows=1 loops=1)
  Filter: (name = 'standard_conforming_strings'::text)
  Rows Removed by Filter: 343
Planning:
  Buffers: shared hit=18
Planning Time: 0.224 ms
Execution Time: 8.555 ms

It is still 10 times slower than the PostgreSQL 11.13 but 40 times faster than the Pg12.

EDIT 2

As noticed by a_horse_with_no_name we don't observe performance problems when using querying current_setting.

explain (analyze, buffers, timing) 
select current_setting('standard_conforming_strings');

returns:

Result  (cost=0.00..0.01 rows=1 width=32) (actual time=0.007..0.008 rows=1 loops=1)
Planning Time: 0.025 ms
Execution Time: 0.022 ms

Answer 1

I've posted the question to the pgsql-performance mailing list and got an answer from Ranier Vilela that updating to latest version of PostgreSQL (v12.8.2) should fix the problem.

He directed me to a message thread discussing the issue. It seems the problem was in libintl library and is now fixed.