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+This document is adapted from README.Debian contained in Debian package.
+
+To use the PostgreSQL exporter, you need to connect to the database with
+superuser (postgres) privileges, or with an user that has been granted enough
+permissions.
+
+The recommended way to do this, is to create a `prometheus` user with no
+password, and then connect using UNIX domain sockets.
+
+To do that, set this connection string in
+/etc/conf.d/prometheus-postgres-exporter:
+
+  DATA_SOURCE_NAME='user=prometheus host=/run/postgresql dbname=postgres'
+
+And use psql (doas -u postgres psql) to execute these SQL commands to create
+the user:
+
+  CREATE USER prometheus;
+  ALTER USER prometheus SET SEARCH_PATH TO prometheus,pg_catalog;
+  
+  CREATE SCHEMA prometheus AUTHORIZATION prometheus;
+  
+  CREATE FUNCTION prometheus.f_select_pg_stat_activity()
+  RETURNS setof pg_catalog.pg_stat_activity
+  LANGUAGE sql
+  SECURITY DEFINER
+  AS $$
+    SELECT * from pg_catalog.pg_stat_activity;
+  $$;
+  
+  CREATE FUNCTION prometheus.f_select_pg_stat_replication()
+  RETURNS setof pg_catalog.pg_stat_replication
+  LANGUAGE sql
+  SECURITY DEFINER
+  AS $$
+    SELECT * from pg_catalog.pg_stat_replication;
+  $$;
+  
+  CREATE VIEW prometheus.pg_stat_replication
+  AS
+    SELECT * FROM prometheus.f_select_pg_stat_replication();
+  
+  CREATE VIEW prometheus.pg_stat_activity
+  AS
+    SELECT * FROM prometheus.f_select_pg_stat_activity();
+  
+  GRANT SELECT ON prometheus.pg_stat_replication TO prometheus;
+  GRANT SELECT ON prometheus.pg_stat_activity TO prometheus;