HPE Vertica live aggregate projection example for user retention - sql

Question

create table events(
id char(36) PRIMARY KEY,
game_id varchar(24) not null,
user_device_id char(36) not null,
event_name varchar(100) not null,
generated_at timestamp with time zone not null
);
SELECT
events.generated_at::DATE AS time_stamp,
COUNT(DISTINCT (
CASE WHEN
events.event_name = 'new_user' THEN events.user_device_id
END
)
) as new_users,
COUNT(DISTINCT (
CASE WHEN
future_events.event_name <> 'new_user' THEN future_events.user_device_id
END
)
) as returned_users,
COUNT(DISTINCT (
CASE WHEN
future_events.event_name <> 'new_user' THEN future_events.user_device_id
END
)) / COUNT(DISTINCT (
CASE WHEN
events.event_name = 'new_user' THEN events.user_device_id
END
))::float as retention
FROM events
LEFT JOIN events AS future_events ON
events.user_device_id = future_events.user_device_id AND
events.generated_at = future_events.generated_at - interval '1 day' AND
events.game_id = future_events.game_id
GROUP BY
time_stamp
ORDER BY
time_stamp;
I am trying to get the Day N ('N' -> any number between 1 to 7) user retention via the above sql query. Due to the fact that I am a noob in HPE vertica, I am not being able to come up the optimum aggregate projection creating statement, Since projection significantly improves the performance of the query.

Answer 1

Aggregated projection won't help with a join query.
You can create a regular projection, segmented and sorted by the join columns, to achieve performance improvement:
CREATE PROJECTION events_p1 (
id,
game_id ENCODING RLE,
user_device_id ENCODING RLE,
event_name,
generated_at ENCODING RLE
) AS
SELECT id,
game_id,
user_device_id,
event_name,
generated_at
FROM events
ORDER BY generated_at,
game_id,
user_device_id
SEGMENTED BY hash(generated_at,game_id,user_device_id) ALL NODES KSAFE 1;