PostgreSQL provides a set of predefined roles
   that provide access to certain, commonly needed, privileged capabilities
   and information.  Administrators (including roles that have the
   CREATEROLE privilege) can GRANT these
   roles to users and/or other roles in their environment, providing those
   users with access to the specified capabilities and information.  For
   example:
GRANT pg_signal_backend TO admin_user;
Care should be taken when granting these roles to ensure they are only used where needed and with the understanding that these roles grant access to privileged information.
The predefined roles are described below. Note that the specific permissions for each of the roles may change in the future as additional capabilities are added. Administrators should monitor the release notes for changes.
pg_checkpoint #
       Allows executing the
       CHECKPOINT command.
      
pg_create_subscription #
       Allows users with CREATE permission on the database to issue
       CREATE SUBSCRIPTION.
      
pg_database_owner #
       Membership consists, implicitly, of the current database owner.  Like
       any role, it can own objects or receive grants of access privileges.
       Consequently, once pg_database_owner has rights
       within a template database, each owner of a database instantiated from
       that template will exercise those rights.
       pg_database_owner cannot be a member of any role, and
       it cannot have non-implicit members.  Initially, this role owns the
       public schema, so each database owner governs local
       use of the schema.
      
pg_maintain #
       Allows executing
       VACUUM,
       ANALYZE,
       CLUSTER,
       REFRESH MATERIALIZED VIEW,
       REINDEX,
       and LOCK TABLE on all
       relations, as if having MAINTAIN rights on those
       objects, even without having it explicitly.
      
pg_read_all_datapg_write_all_data #
       pg_read_all_data allows reading all data (tables,
       views, sequences), as if having SELECT rights on
       those objects, and USAGE rights on all schemas, even without having it
       explicitly.  This role does not have the role attribute
       BYPASSRLS set.  If RLS is being used, an
       administrator may wish to set BYPASSRLS on roles
       which this role is GRANTed to.
      
       pg_write_all_data allows writing all data (tables,
       views, sequences), as if having INSERT,
       UPDATE, and DELETE rights on those
       objects, and USAGE rights on all schemas, even without having it
       explicitly.  This role does not have the role attribute
       BYPASSRLS set.  If RLS is being used, an
       administrator may wish to set BYPASSRLS on roles
       which this role is GRANTed to.
      
pg_read_all_settingspg_read_all_statspg_stat_scan_tablespg_monitor #These roles are intended to allow administrators to easily configure a role for the purpose of monitoring the database server. They grant a set of common privileges allowing the role to read various useful configuration settings, statistics, and other system information normally restricted to superusers.
       pg_read_all_settings allows reading all configuration
       variables, even those normally visible only to superusers.
      
       pg_read_all_stats allows reading all pg_stat_* views
       and use various statistics related extensions, even those normally
       visible only to superusers.
      
       pg_stat_scan_tables allows executing monitoring
       functions that may take ACCESS SHARE locks on tables,
       potentially for a long time.
      
       pg_monitor allows reading/executing various
       monitoring views and functions.  This role is a member of
       pg_read_all_settings,
       pg_read_all_stats and
       pg_stat_scan_tables.
      
pg_read_server_filespg_write_server_filespg_execute_server_program #These roles are intended to allow administrators to have trusted, but non-superuser, roles which are able to access files and run programs on the database server as the user the database runs as. As these roles are able to access any file on the server file system, they bypass all database-level permission checks when accessing files directly and they could be used to gain superuser-level access, therefore great care should be taken when granting these roles to users.
       pg_read_server_files allows reading files from any
       location the database can access on the server with COPY and other
       file-access functions.
      
       pg_write_server_files allows writing to files in any
       location the database can access on the server with COPY any other
       file-access functions.
      
       pg_execute_server_program allows executing programs
       on the database server as the user the database runs as with COPY and
       other functions which allow executing a server-side program.
      
pg_signal_backend #Allows signaling another backend to cancel a query or terminate its session. A user granted this role cannot however send signals to a backend owned by a superuser. See Section 9.28.2.
pg_use_reserved_connections #Allows use of connection slots reserved via reserved_connections.