--
-- Quoting helpers: quote_literal, quote_nullable, quote_ident.
--
CREATE FUNCTION q_all(text) RETURNS text LANGUAGE plruby AS $$
    "lit=#{quote_literal(args[0])} " +
        "null=#{quote_nullable(args[0])} " +
        "ident=#{quote_ident(args[0])}"
$$;
SELECT q_all('plain');
                q_all                 
--------------------------------------
 lit='plain' null='plain' ident=plain
(1 row)

SELECT q_all($$O'Reilly$$);
                       q_all                       
---------------------------------------------------
 lit='O''Reilly' null='O''Reilly' ident="O'Reilly"
(1 row)

SELECT q_all('a"b');
               q_all               
-----------------------------------
 lit='a"b' null='a"b' ident="a""b"
(1 row)

SELECT q_all('back\slash');
                           q_all                           
-----------------------------------------------------------
 lit=E'back\\slash' null=E'back\\slash' ident="back\slash"
(1 row)

-- nil: quote_nullable yields NULL, quote_literal coerces to the empty literal.
CREATE FUNCTION q_nil() RETURNS text LANGUAGE plruby AS $$
    "null=#{quote_nullable(nil)} lit=#{quote_literal(nil)}"
$$;
SELECT q_nil();
      q_nil       
------------------
 null=NULL lit=''
(1 row)

-- The quoted forms are usable as identifiers and literals in generated SQL.
CREATE TABLE "weird name" (id int);
CREATE FUNCTION q_use(text) RETURNS int LANGUAGE plruby AS $$
    spi_exec("insert into #{quote_ident('weird name')} values " +
             "(length(#{quote_literal(args[0])}))")
    spi_fetch_row(spi_exec("select max(id) as m from #{quote_ident('weird name')}"))['m']
$$;
SELECT q_use('abcde');
 q_use 
-------
     5
(1 row)

DROP TABLE "weird name";