DO

Runs anonymous code block as a transient anonymous function.

Synopsis

DO [ LANGUAGE <lang_name> ] <code>

Description

DO Runs 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 run a single time.

The optional LANGUAGE clause can appear either before or after the code block.

Anonymous blocks are procedural language structures that provide the capability to create and run procedural code on the fly without persistently storing the code as database objects in the system catalogs. The concept of anonymous blocks is similar to UNIX shell scripts, which enable several manually entered commands to be grouped and run as one step. As the name implies, anonymous blocks do not have a name, and for this reason they cannot be referenced from other objects. Although built dynamically, anonymous blocks can be easily stored as scripts in the operating system files for repetitive execution.

Anonymous blocks are standard procedural language blocks. They carry the syntax and obey the rules that apply to the procedural language, including declaration and scope of variables, execution, exception handling, and language usage.

The compilation and execution of anonymous blocks are combined in one step, while a user-defined function needs to be re-defined before use each time its definition changes.

Parameters

code : The procedural language code to be run. This must be specified as a string literal, just as with the CREATE FUNCTION command. Use of a dollar-quoted literal is recommended. Optional keywords have no effect. These procedural languages are supported: PL/pgSQL (plpgsql), PL/Python (plpythonu), and PL/Perl (plperl and plperlu).

lang_name : The name of the procedural language that the code is written in. The default is plpgsql. The language must be installed on the LightDB-A Database system and registered in the database.

Notes

The PL/pgSQL language is installed on the LightDB-A Database system and is registered in a user created database. The PL/Python and PL/Perl languages are installed by default, but not registered. Other languages are not installed or registered. The system catalog pg_language contains information about the registered languages in a database.

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.

Anonymous blocks do not support function volatility or EXECUTE ON attributes.

Examples

This PL/pgSQL example grants all privileges on all views in schema public to role webuser:

DO $$DECLARE r record;
BEGIN
    FOR r IN SELECT table_schema, table_name FROM information_schema.tables
             WHERE table_type = 'VIEW' AND table_schema = 'public'
    LOOP
        EXECUTE 'GRANT ALL ON ' || quote_ident(r.table_schema) || '.' || quote_ident(r.table_name) || ' TO webuser';
    END LOOP;
END$$;

This PL/pgSQL example determines if a LightDB-A Database user is a superuser. In the example, the anonymous block retrieves the input value from a temporary table.

CREATE TEMP TABLE list AS VALUES ('gpadmin') DISTRIBUTED RANDOMLY;

DO $$ 
DECLARE
  name TEXT := 'gpadmin' ;
  superuser TEXT := '' ;
  t1_row   pg_authid%ROWTYPE;
BEGIN
  SELECT * INTO t1_row FROM pg_authid, list 
     WHERE pg_authid.rolname = name ;
  IF t1_row.rolsuper = 'f' THEN
    superuser := 'not ';
  END IF ;
  RAISE NOTICE 'user % is %a superuser', t1_row.rolname, superuser ;
END $$ LANGUAGE plpgsql ;

Note The example PL/pgSQL uses SELECT with the INTO clause. It is different from the SQL command SELECT INTO.

Compatibility

There is no DO statement in the SQL standard.