bitmap_union | VeloDB

bitmap_union function

This is an aggregate function used to calculate the union of bitmaps after group. It is often used in scenarios such as PV and UV calculation.

Syntax:

BITMAP BITMAP_UNION(BITMAP value)

You enter a set of bitmap values; the function calculates the union of this set of bitmap values and returns a result.

mysql> select page_id, bitmap_union(user_id) from table group by page_id;

Combined with the bitmap_count function, the PV data of the web page can be obtained

mysql> select page_id, bitmap_count(bitmap_union(user_id)) from table group by page_id;

When the user_id field is int, the above query semantics is equivalent to

mysql> select page_id, count(distinct user_id) from table group by page_id;

BITMAP_UNION, BITMAP