--Витрина dm.lesson_popularity_summary
CREATE MATERIALIZED VIEW dm.lesson_popularity_summary as
select 
	l.lesson_id,
	l.title as lesson_title,
	c.course_id,
	c.title as course_title,
	COUNT(f.user_id) as total_views,
	COUNT(DISTINCT f.user_id) as unique_users,
	MIN(f.viewed_at) as first_view,
	MAX(f.viewed_at) as last_view
FROM core.fact_lesson_views f
JOIN core.dim_lesson l
    ON f.lesson_id = l.lesson_id
JOIN core.dim_course c
    ON l.course_id = c.course_id
GROUP BY
    l.lesson_id,
    l.title,
    c.course_id,
    c.title
order by lesson_id;

select * from dm.lesson_popularity_summary;

--Удалил лишний индекс
DROP INDEX core.idx_fact_views_course_id;

-- Все индексы для  CORE-таблиц
SELECT 
    tablename,
    indexname,
    indexdef
FROM pg_indexes 
WHERE schemaname = 'core'
  AND tablename IN (
      'dim_course',
      'dim_date', 
      'dim_lesson',
      'dim_user',
      'enrollments',
      'fact_lesson_views'
  )
ORDER by indexname, tablename;


--Витрина dm.inactive_users_summary
CREATE MATERIALIZED VIEW dm.inactive_users_summary as
select
	du.user_id,
	du.name as user_name,
	du.email,
	du.age,
	COUNT(e.course_id) as enrollments_count,
	du.registration_date
from core.dim_user du
left join core.enrollments e
	on du.user_id = e.user_id
left join core.fact_lesson_views flv
	on du.user_id = flv.user_id
where flv.user_id is NULL
group by
	du.user_id,
	du.name,
	du.email,
	du.age,
	du.registration_date
order by du.user_id;

select * from dm.inactive_users_summary;

--Витрина dm.course_completion_rate
CREATE MATERIALIZED VIEW dm.course_completion_rate as
select
	du.user_id,
	du.name as user_name,
	dc.course_id,
	dc.title as course_title,
	COUNT(DISTINCT dl.lesson_id) AS lessons_in_course,
	COUNT(DISTINCT flv.lesson_id) AS lessons_viewed,
	ROUND(COUNT(DISTINCT flv.lesson_id)::numeric / NULLIF(COUNT(DISTINCT dl.lesson_id), 0), 2) AS completion_rate
from core.enrollments e
left join core.dim_user du
    on du.user_id = e.user_id
left join core.dim_course dc
    on dc.course_id = e.course_id
left join core.dim_lesson dl
    on dl.course_id = e.course_id
left join core.fact_lesson_views flv
    on flv.user_id = e.user_id
   and flv.lesson_id = dl.lesson_id
group by
    du.user_id,
	du.name,
	dc.course_id,
	dc.title
order by du.user_id;

select * from dm.course_completion_rate order by user_id;

--Этап 5. Проверка 
SELECT * FROM dm.lesson_popularity_summary LIMIT 10;
SELECT * FROM dm.inactive_users_summary LIMIT 10;
SELECT * FROM dm.course_completion_rate LIMIT 10;
--Все витрины отображаются корректно. Скрины: "название витрины".png