BUG #15640: FATAL: XX000: cannot read pg_class without having selected a database

The following bug has been logged on the website:

Bug reference:      15640
Logged by:          Mikhail Kiyanov
Email address:      m.kiianov@rtk-dc.ru
PostgreSQL version: 9.6.11
Operating system:   Debian GNU/Linux 9.1 (stretch)
Description:

Hi!
We are currently having a problems with our production database.
The problem is that database goes to crash and after that put into recovery
mode with the following errors. Please see log files.

2019-02-18 05:30:35 GMT [40461]: [28685-1] db=vc_production,user=estore
LOCATION:  exec_execute_message, postgres.c:2052
2019-02-18 05:30:36 GMT [45739]: [1-1] db=,user= LOG:  00000: automatic
analyze of table "template1.pg_catalog.pg_shdepend" system usage: CPU
0.00s/0.00u sec
elapsed 0.07 sec
2019-02-18 05:30:36 GMT [45739]: [2-1] db=,user= LOCATION:  do_analyze_rel,
analyze.c:665
2019-02-18 05:30:36 GMT [40378]: [2-1] db=,user= FATAL:  XX000: cannot read
pg_class without having selected a database
2019-02-18 05:30:36 GMT [40378]: [3-1] db=,user= LOCATION:  ScanPgRelation,
relcache.c:314
2019-02-18 05:30:36 GMT [40267]: [7-1] db=,user= LOG:  00000: autovacuum
launcher process (PID 40378) exited with exit code 1
2019-02-18 05:30:36 GMT [40267]: [8-1] db=,user= LOCATION:  LogChildExit,
postmaster.c:3552
2019-02-18 05:30:36 GMT [40267]: [9-1] db=,user= LOG:  00000: terminating
any other active server processes
2019-02-18 05:30:36 GMT [40267]: [10-1] db=,user= LOCATION:
HandleChildCrash, postmaster.c:3294
2019-02-18 05:30:36 GMT [44893]: [5-1] db=vc_production,user=vcfront
WARNING:  57P02: terminating connection because of crash of another server
process
2019-02-18 05:30:36 GMT [44893]: [6-1] db=vc_production,user=vcfront DETAIL:
 The postmaster has commanded this server process to roll back the current
transaction and exit, because another server process exited abnormally and
possibly corrupted shared memory.

It happened several times. And everytime it happens at different time.

Some addtitional information about our server:

postgres=# select version();
                                                               version
                                                         

--------------------------------------------------------------------------------------------------------------------------------------
 PostgreSQL 9.6.11 on x86_64-pc-linux-gnu (Debian 9.6.11-1.pgdg90+1),
compiled by gcc (Debian 6.3.0-18+deb9u1) 6.3.0 20170516, 64-bit
(1 row)

$ cat /etc/postgresql/9.6/main/postgresql.conf

shared_preload_libraries = 'pg_stat_statements, timescaledb,
pg_wait_sampling, repmgr, auto_explain'
track_io_timing = on
listen_addresses = '0.0.0.0'
port = 5432
superuser_reserved_connections = 3
unix_socket_group = ''
unix_socket_permissions = 0777
log_filename = 'postgresql-%a.log'
log_rotation_age = 1d
log_truncate_on_rotation = on
log_line_prefix = '%t [%p]: [%l-1] db=%d,user=%u '
log_lock_waits = on
log_temp_files = 0
log_connections = on
log_checkpoints = on
log_disconnections = on
log_directory = '/storage/log/postgresql'

log_error_verbosity = verbose

logging_collector = on
log_min_duration_statement = 1000
log_autovacuum_min_duration = 10
checkpoint_completion_target = 0.9
checkpoint_timeout = 30min
effective_cache_size = 200GB
shared_buffers = 32GB
fsync = on
autovacuum_max_workers = 25
bgwriter_delay = 10
bgwriter_lru_maxpages = 800
vacuum_cost_delay = 1
autovacuum_analyze_scale_factor = 0.01
data_directory = '/var/lib/postgresql/9.6/main'
hba_file = '/etc/postgresql/9.6/main/pg_hba.conf'

# master specific
wal_level = 'hot_standby'
max_wal_senders = 10
max_replication_slots = 9
wal_keep_segments = 100
max_connections = 500
work_mem = 400MB
max_wal_size = 140GB
min_wal_size = 40GB
autovacuum_work_mem = 11GB
autovacuum_vacuum_scale_factor = 0.01
autovacuum_freeze_max_age = 1000000000
autovacuum_multixact_freeze_max_age = 800000000
autovacuum_naptime = 1
maintenance_work_mem = 4096MB
random_page_cost = 1
synchronous_commit = off

# Extentions
auto_explain.log_min_duration = '5s'

vc_production=# select extname,extversion from pg_extension;
      extname       | extversion
--------------------+------------
 plpgsql            | 1.0
 pageinspect        | 1.5
 citext             | 1.3
 pg_buffercache     | 1.2
 pg_stat_statements | 1.4
 pgstattuple        | 1.4
 pg_repack          | 1.4.4
 pg_wait_sampling   | 1.1
 timescaledb        | 0.8.0
(9 rows)

Some tables have personal autovacuum settings:

vc_production=# \d+ estore.events_0
                                                            Table
"estore.events_0"
   Column   |            Type             |
Modifiers                          | Storage  | Stats target | Description

------------+-----------------------------+------------------------------------------------------------+----------+--------------+-------------
 id         | bigint                      | not null default
nextval('estore.events_id_seq'::regclass) | plain    |              |
 camera_uid | text                        | not null
                          | extended |              |
 source     | smallint                    | not null
                          | plain    |              |
 kind       | integer                     | not null
                          | plain    |              |
 begin      | timestamp without time zone | not null
                          | plain    |              |
 end        | timestamp without time zone |
                          | plain    |              |
 properties | jsonb                       | not null
                          | extended |              |
 is_active  | boolean                     | not null
                          | plain    |              |
Indexes:
    "events_0_pkey" PRIMARY KEY, btree (id), tablespace "local_01_ts"
    "events_0_camera_uid_begin_idx" btree (camera_uid, begin), tablespace
"local_01_ts"
    "events_0_camera_uid_end_idx" btree (camera_uid, "end"), tablespace
"local_01_ts"
    "events_0_camera_uid_expr_idx" btree (camera_uid, (properties ->>
'uid'::text)), tablespace "local_01_ts"
    "events_0_camera_uid_kind_source_idx" btree (camera_uid, kind, source),
tablespace "local_01_ts"
    "events_0_camera_uid_source_begin_end_idx" btree (camera_uid, source,
begin, "end"), tablespace "local_01_ts"
    "events_0_end_idx" btree ("end"), tablespace "local_01_ts"
    "events_0_src_knd_cmr_uid_prpt_idx" btree (source, kind, camera_uid,
(properties ->> 'channel_uid'::text)), tablespace "local_01_ts"
Check constraints:
    "events_0_camera_uid_check" CHECK (camera_uid >= '0'::text AND
camera_uid < '1'::text)
Inherits: estore.events
Tablespace: "estore_ts"
Options: autovacuum_vacuum_scale_factor=0.001

vc_production=# \d+ violet.alarm_events
                                                             Table
"violet.alarm_events"
   Column   |            Type             |
Modifiers                             | Storage  | Stats target |
Description

------------+-----------------------------+------------------------------------------------------------------+----------+--------------+-------------
 id         | bigint                      | not null default
nextval('violet.alarm_events_id_seq'::regclass) | plain    |
|
 camera_id  | integer                     | not null
                                | plain    |              |
 kind       | integer                     | not null
                                | plain    |              |
 begin      | timestamp without time zone | not null
                                | plain    |              |
 end        | timestamp without time zone |
                                | plain    |              |
 uid        | text                        | not null
                                | extended |              |
 properties | jsonb                       | not null default '{}'::jsonb
                                | extended |              |
 created_at | timestamp without time zone | not null default now()
                                | plain    |              |
 updated_at | timestamp without time zone | not null default now()
                                | plain    |              |
 deleted_at | timestamp without time zone |
                                | plain    |              |
Indexes:
    "alarm_events_new_pkey" PRIMARY KEY, btree (id), tablespace
"violet_ts"
    "alarm_events_new_begin_camera_id_idx" btree (begin, camera_id),
tablespace "violet_ts"
    "alarm_events_new_begin_idx" btree (begin), tablespace "violet_ts"
    "alarm_events_new_camera_id_idx" btree (camera_id), tablespace
"violet_ts"
    "alarm_events_new_camera_id_uid_idx" btree (camera_id, uid), tablespace
"violet_ts"
Foreign-key constraints:
    "alarm_events_camera_id_fkey" FOREIGN KEY (camera_id) REFERENCES
violet.cameras(id)
Tablespace: "violet_ts"
Options: autovacuum_vacuum_cost_delay=0,
autovacuum_vacuum_scale_factor=0.00001

This is a physical server with:
$ free -m
              total        used        free      shared  buff/cache
available
Mem:         515897       47349        4112       34023      464436
431171
Swap:             0           0           0

$ grep 'processor' -c /proc/cpuinfo
80

model name      : Intel(R) Xeon(R) CPU E5-2698 v4 @ 2.20GHz

The database located on ssd disks.

This database is mission critical for our business.
Would you be so kind to help us with our problem.