Note: At present, this section is just taken from PostgreSQL documentation and is subject to revision for Postgres-XC.
DO executes an anonymous code block, or in other words a transient anonymous function in a procedural language.
The code block is treated as though it were the body of a function with no parameters, returning void. It is parsed and executed a single time.
The optional LANGUAGE clause can be written either before or after the code block.
The procedural language code to be executed. This must be specified as a string literal, just as in CREATE FUNCTION. Use of a dollar-quoted literal is recommended.
The name of the procedural language the code is written in. If omitted, the default is plpgsql.
The procedural language to be used must already have been installed into the current database by means of CREATE LANGUAGE. plpgsql is installed by default, but other languages are not.
The user must have USAGE privilege for the procedural language, or must be a superuser if the language is untrusted. This is the same privilege requirement as for creating a function in the language.
Grant all privileges on all views in schema public to role webuser:
DO $$DECLARE r record;
BEGIN
FOR r IN SELECT table_schema, table_name FROM information_schema.tables
WHERE table_type = 'VIEW' AND table_schema = 'public'
LOOP
EXECUTE 'GRANT ALL ON ' || quote_ident(r.table_schema) || '.' || quote_ident(r.table_name) || ' TO webuser';
END LOOP;
END$$;