/*
 - ВИТРИНА АНАЛИЗА ПОПУЛЯРНОСТИ КАЖДОГО УРОКА
 - ВСЕ УЧАСТВУЮЩИЕ ИЗМЕРЕНИЯ DISTRIBUTED REPLICATED
 - ИТОГОВОЕ ПРЕДСТВАЛЕНИЕ DISTRIBUTED BY (lesson_id, course_id)
 */

CREATE MATERIALIZED VIEW IF NOT EXISTS dm.lesson_popularity_summary AS
-- EXPLAIN ANALYZE
WITH t1 AS (
SELECT 
	lesson_id,
	course_id,
	COUNT(lesson_id) AS total_views,
	COUNT(DISTINCT user_id) AS unique_users,
	MIN(viewed_at)AS first_view,
	MAX(viewed_at)AS last_view
FROM core.fact_lesson_views
GROUP BY lesson_id, course_id
),
t2 AS (
SELECT 
	l.lesson_id,
	l.title AS lesson_title,
	c.course_id,
	c.title AS course_title
FROM core.dim_course c 
LEFT JOIN core.dim_lesson l USING(course_id)

)
SELECT 
	t1.lesson_id,
	t2.lesson_title,
	t1.course_id,
	t2.course_title,
	t1.total_views,
	t1.unique_users,
	t1.first_view,
	t1.last_view
FROM t1
LEFT JOIN t2 USING(lesson_id)

DISTRIBUTED BY (lesson_id, course_id);