BITMAP_UNION_COUNT

Description

Calculates the union of input Bitmaps and returns its cardinality.

Syntax

BITMAP_UNION_COUNT(<expr>)

Arguments

Argument	Description
<expr>	Data type supporting Bitmap

Return Value

Returns the size of the Bitmap union, i.e., the number of distinct elements. If there is no valid data in the group, returns 0.

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_union_count(user_id) from pv_bitmap;

Counts the number of distinct user_id values.

+-----------------------------+
| bitmap_union_count(user_id) |
+-----------------------------+
|                           3 |
+-----------------------------+

select bitmap_union_count(user_id) from pv_bitmap where user_id is null;

+-----------------------------+
| bitmap_union_count(user_id) |
+-----------------------------+
|                           0 |
+-----------------------------+