---

{ “title”: “BITMAP_INTERSECT”, “language”: “en”, “description”: “Used to calculate the intersection of grouped Bitmaps. Common use case: calculating user retention.” }

Description

Used to calculate the intersection of grouped Bitmaps. Common use case: calculating user retention.

Syntax

BITMAP_INTERSECT(BITMAP <value>)

Arguments

Argument	Description
<value>	Data type supporting Bitmap

Return Value

Returns a value of Bitmap type. If there is no valid data in the group, returns NULL.

Example

Example

-- setup
CREATE TABLE user_tags (
	tag VARCHAR(20),
	date DATETIME,
	user_id BITMAP bitmap_union
) AGGREGATE KEY(tag, date) DISTRIBUTED BY HASH(tag) BUCKETS 1
PROPERTIES ("replication_num" = "1");
INSERT INTO user_tags VALUES
	('A', '2020-05-18', to_bitmap(1)),
	('A', '2020-05-18', to_bitmap(2)),
	('A', '2020-05-19', to_bitmap(2)),
	('A', '2020-05-19', to_bitmap(3)),
	('B', '2020-05-18', to_bitmap(4)),
	('B', '2020-05-19', to_bitmap(4)),
	('B', '2020-05-19', to_bitmap(5));

select tag, bitmap_to_string(bitmap_intersect(user_id)) from (
	select tag, date, bitmap_union(user_id) user_id from user_tags where date in ('2020-05-18', '2020-05-19') group by tag, date
) a group by tag;

Query the user retention for different tags between today and yesterday.

+------+---------------------------------------------+
| tag  | bitmap_to_string(bitmap_intersect(user_id)) |
+------+---------------------------------------------+
| A    | 2                                           |
| B    | 4                                           |
+------+---------------------------------------------+

select bitmap_to_string(bitmap_intersect(user_id)) from user_tags where tag is null;

+---------------------------------------------+
| bitmap_to_string(bitmap_intersect(user_id)) |
+---------------------------------------------+
|                                             |
+---------------------------------------------+