I've seen this message now a handful of times recently. It seems to happen overnight, during a maintenance job which reindex things, including system catalog indices.
It's easy to reproduce error under 10.5, but not under 10.3 nor 10.4. while :; do for a in pg_class_oid_index pg_class_relname_nsp_index pg_class_tblspc_relfilenode_index; do psql ts -qc "REINDEX INDEX $a"; done; done& [pryzbyj@database ~]$ while :; do psql ts -qc ''; done psql: FATAL: could not read block 1 in file "base/16400/313430687": read only 0 of 8192 bytes psql: FATAL: could not read block 0 in file "base/16400/313430708": read only 0 of 8192 bytes psql: FATAL: could not read block 0 in file "base/16400/313430711": read only 0 of 8192 bytes ^C postgres=# SELECT * FROM postgres_log WHERE error_severity ='FATAL'; log_time | 2018-08-28 22:19:58.822-05 user_name | telsasoft database | ts pid | 22445 connection_from | 192.168.122.12:58318 session_id | 5b8610de.57ad session_line | 1 command_tag | startup session_start_time | 2018-08-28 22:19:58-05 virtual_transaction_id | 26/280967 transaction_id | 0 error_severity | FATAL sql_state_code | XX001 message | could not read block 0 in file "base/16400/313316300": read only 0 of 8192 bytes Justin
