---

{ “title”: “BITMAP_UNION”, “language”: “en”, “description”: “Calculates the union of input Bitmaps and returns a new Bitmap.” }

Description

Calculates the union of input Bitmaps and returns a new Bitmap.

Syntax

BITMAP_UNION(<expr>)

Arguments

Argument	Description
<expr>	Data type supporting Bitmap

Return Value

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

Example

-- setup
CREATE TABLE pv_bitmap (
  dt INT,
  page INT,
  user_id BITMAP
) DISTRIBUTED BY HASH(dt) BUCKETS 1
PROPERTIES ("replication_num" = "1");
INSERT INTO pv_bitmap VALUES
  (1, 100, to_bitmap(100)),
  (1, 100, to_bitmap(200)),
  (1, 100, to_bitmap(300)),
  (2, 200, to_bitmap(300));

select bitmap_to_string(bitmap_union(user_id)) from pv_bitmap;

+-----------------------------------------+
| bitmap_to_string(bitmap_union(user_id)) |
+-----------------------------------------+
| 100,200,300                             |
+-----------------------------------------+

select bitmap_to_string(bitmap_union(user_id)) from pv_bitmap where user_id is null;

+-----------------------------------------+
| bitmap_to_string(bitmap_union(user_id)) |
+-----------------------------------------+
|                                         |
+-----------------------------------------+