Paginating SQL function

paginated.sql

CREATE OR REPLACE FUNCTION list_paginated_messages_by_priority(p text, o int, l int) 
RETURNS TABLE(id bigint, sender_name text, recipient_name text, message_title text, current_page bigint, page_count bigint) 
LANGUAGE SQL
BEGIN ATOMIC
	WITH pagination_meta_data AS (
		SELECT *,  
			((ROW_NUMBER () OVER (ORDER BY id) - 1) / $3) + 1 AS current_page, 
			CEILING((COUNT(*) OVER ())::decimal  / $3::decimal)::bigint AS page_count 
		FROM (
			SELECT *, 
				ROW_NUMBER () OVER (PARTITION BY id ORDER BY id DESC NULLS LAST, id DESC) AS this_rows_number
			FROM direct_message
		) sub
		WHERE this_rows_number = 1
		AND $1 = ANY(message_priority::text[])
	)
	SELECT id,
		(SELECT pn.first_name || ' ' || pn.last_name FROM person pn WHERE sender_id = pn.id) AS sender_name,
		(SELECT pn.first_name || ' ' || pn.last_name FROM person pn WHERE recipient_id = pn.id) AS recipient_name,
		message_title,
		current_page,
		page_count
	FROM pagination_meta_data
	ORDER BY current_page ASC
	LIMIT $3
	OFFSET $2;
END;