Why do "pg_buffercache" and "pg_stat_statements" show up in the log as not installed?

Question

linux

postgresql-9.5
Installed extensions
CREATE EXTENSION pg_buffercache
CREATE EXTENSION pg_stat_statements
Postgresql.conf changes

shared_preload_libraries = 'pg_stat_statements'         
pg_stat_statements.track = all

Checking installed extensions

\dx
+--------------------+-----------+------------+-----------------------------------------------------------+
| Name               | Version   | Schema     | Description                                               |
|--------------------+-----------+------------+-----------------------------------------------------------|
| pg_buffercache     | 1.1       | public     | examine the shared buffer cache                           |
| pg_stat_statements | 1.3       | public     | track execution statistics of all SQL statements executed |
| plpgsql            | 1.0       | pg_catalog | PL/pgSQL procedural language                              |
+--------------------+-----------+------------+-----------------------------------------------------------+

\dx+
Objects in extension "pg_buffercache"
+-------------------------------------------+
| Object Description                        |
|-------------------------------------------|
| function plpgsql_call_handler()           |
| function plpgsql_inline_handler(internal) |
| function plpgsql_validator(oid)           |
| language plpgsql                          |
+-------------------------------------------+
SELECT 2
Objects in extension "pg_stat_statements"
+----------------------+
| Object Description   |
|----------------------|
+----------------------+
SELECT 3
Objects in extension "plpgsql"
+----------------------+
| Object Description   |
|----------------------|
+----------------------+

But there is an error in the logs

[email protected] ERROR:  relation "pg_stat_statements" does not exist at character 62

[email protected] ERROR:  relation "pg_buffercache" does not exist at character 511

ERROR:  function pg_size_bytes(text) does not exist at character 36

I also installed the `fuzzystrmatch` extension with a different public/pg_catalog schema.
I tried to remove the extension and reinstall it. but didn't help.

Answer 1

https://github.com/lesovsky/zabbix-extensions/issues/49
bug from the developer on 9.6 everything works