Postgres: Subquery with GROUP BY - sql

Question

I'm trying to optimize a query (instead of repeating it a lot of time), with this NOT FUNCTIONAL CODE above (since subqueries only return 1 column):
SELECT
e.pageview_identifier,
e.created_at,
e.pageview_current_url,
e.pageview_mobile,
(
SELECT event_type, COUNT(event_identifier)
FROM events v
WHERE
v.company_identifier = e.company_identifier AND
v.user_identifier = e.user_identifier AND
v.pageview_identifier = e.pageview_identifier
GROUP BY v.event_type
)
FROM events e
WHERE
company_identifier = 'xyz' AND
user_identifier = '01CDQZVSJFBDA8W444JS2CS3BA' AND
event_type = 'page:view';
Basically, I want to retrieve the columns as
pageview_identifier, created_at, ..., event_type_a_count, event_type_b_count, ...
A FUNCTIONAL code that works is:
SELECT
e.pageview_identifier,
e.created_at,
e.pageview_current_url,
e.pageview_mobile,
(
SELECT COUNT(event_identifier)
FROM events v
WHERE
v.company_identifier = e.company_identifier AND
v.user_identifier = e.user_identifier AND
v.pageview_identifier = e.pageview_identifier AND
v.event_type = 'mouse:move'
) as mouse_move_count
FROM events e
WHERE
company_identifier = 'xyz' AND
user_identifier = '01CDQZVSJFBDA8W444JS2CS3BA' AND
event_type = 'page:view';
But in this case, I would need to repeat a lot of time this subquery for each kind of event_type.
Edit 1 - More information:
On my WHERE clause, I restrict it to only event_type = 'page:view'. I have some possible values for event_type, and for each page:view, I need to count related events (with different event_type) to it based on the condition e.pageview_identifier = v.pageview_identifier.

Answer 1

Just use a window function:
SELECT e.pageview_identifier,
e.created_at,
e.pageview_current_url,
e.pageview_mobile,
COUNT(*) OVER (PARTITION BY e.company_identifier, e.user_identifier, e.pageview_identifier) as cnt
FROM events e
WHERE e.company_identifier = 'xyz' AND
e.user_identifier = '01CDQZVSJFBDA8W444JS2CS3BA' AND
e.event_type = 'page:view';
Note: This counts only 'page:view' events. If you want a count of each event, then one way is:
SELECT e.*
FROM (SELECT e.pageview_identifier,
e.created_at,
e.pageview_current_url,
e.pageview_mobile,
COUNT(*) FILTER (WHERE .event_type = 'mouse:move') OVER (PARTITION BY e.company_identifier, e.user_identifier, e.pageview_identifier) as cnt_mouse_move,
COUNT(*) FILTER (WHERE .event_type = ''page:view'') OVER (PARTITION BY e.company_identifier, e.user_identifier, e.pageview_identifier) as cnt_page_view,
. . .
FROM events e
WHERE e.company_identifier = 'xyz' AND
e.user_identifier = '01CDQZVSJFBDA8W444JS2CS3BA'
) e
WHERE e.event_type = 'page:view';