create or replace function pgq.maint_operations(out func_name text, out func_arg text)
returns setof record as $$
-- ----------------------------------------------------------------------
-- Function: pgq.maint_operations(0)
--
--      Returns list of functions to call for maintenance.
--
--      The goal is to avoid hardcoding them into maintenance process.
--
-- Function signature:
--      Function should take either 1 or 0 arguments and return 1 if it wants
--      to be called immediately again, 0 if not.
--
-- Returns:
--      func_name   - Function to call
--      func_arg    - Optional argument to function (queue name)
-- ----------------------------------------------------------------------
declare
    ops text[];
    nrot int4;
begin
    -- rotate step 1
    nrot := 0;
    func_name := 'pgq.maint_rotate_tables_step1';
    for func_arg in
        select queue_name from pgq.queue
            where queue_rotation_period is not null
                and queue_switch_step2 is not null
                and queue_switch_time + queue_rotation_period < current_timestamp
            order by 1
    loop
        nrot := nrot + 1;
        return next;
    end loop;

    -- rotate step 2
    if nrot = 0 then
        select count(1) from pgq.queue
            where queue_rotation_period is not null
                and queue_switch_step2 is null
            into nrot;
    end if;
    if nrot > 0 then
        func_name := 'pgq.maint_rotate_tables_step2';
        func_arg := NULL;
        return next;
    end if;

    -- check if extra field exists
    perform 1 from pg_attribute
      where attrelid = 'pgq.queue'::regclass
        and attname = 'queue_extra_maint';
    if found then
        -- add extra ops
        for func_arg, ops in
            select q.queue_name, queue_extra_maint from pgq.queue q
             where queue_extra_maint is not null
             order by 1
        loop
            for i in array_lower(ops, 1) .. array_upper(ops, 1)
            loop
                func_name = ops[i];
                return next;
            end loop;
        end loop;
    end if;

    -- vacuum tables
    func_name := 'vacuum';
    for func_arg in
        select * from pgq.maint_tables_to_vacuum()
    loop
        return next;
    end loop;

    --
    -- pgq_node & londiste
    --
    -- although they belong to queue_extra_maint, they are
    -- common enough so its more effective to handle them here.
    --

    perform 1 from pg_proc p, pg_namespace n
      where p.pronamespace = n.oid
        and n.nspname = 'pgq_node'
        and p.proname = 'maint_watermark';
    if found then
        func_name := 'pgq_node.maint_watermark';
        for func_arg in
            select n.queue_name
              from pgq_node.node_info n
              where n.node_type = 'root'
        loop
            return next;
        end loop;

    end if;

    perform 1 from pg_proc p, pg_namespace n
      where p.pronamespace = n.oid
        and n.nspname = 'londiste'
        and p.proname = 'root_check_seqs';
    if found then
        func_name := 'londiste.root_check_seqs';
        for func_arg in
            select distinct s.queue_name
              from londiste.seq_info s, pgq_node.node_info n
              where s.local
                and n.node_type = 'root'
                and n.queue_name = s.queue_name
        loop
            return next;
        end loop;
    end if;

    perform 1 from pg_proc p, pg_namespace n
      where p.pronamespace = n.oid
        and n.nspname = 'londiste'
        and p.proname = 'periodic_maintenance';
    if found then
        func_name := 'londiste.periodic_maintenance';
        func_arg := NULL;
        return next;
    end if;

    return;
end;
$$ language plpgsql;