bitmap_to_binary
Description
Converts Bitmap values to a Binary string.
bitmap_to_binary is mainly used for exporting Bitmap data. The compression effect is better than bitmap_to_base64.
If you plan to export data directly to a binary file such as Parquet, this function is recommended.
This function is supported from v3.0.
Syntax
VARBINARY bitmap_to_binary(BITMAP bitmap)
Parameters
bitmap
: the Bitmap to convert, required. If the input value is invalid, an error is returned.
Return value
Returns a value of the VARBINARY type.
Examples
Example 1: Use this function with other bitmap functions.
mysql> select hex(bitmap_to_binary(bitmap_from_string("0, 1, 2, 3")));
+---------------------------------------------------------+
| hex(bitmap_to_binary(bitmap_from_string('0, 1, 2, 3'))) |
+---------------------------------------------------------+
| 023A3000000100000000000300100000000000010002000300 |
+---------------------------------------------------------+
1 row in set (0.01 sec)
mysql> select hex(bitmap_to_binary(to_bitmap(1)));
+-------------------------------------+
| hex(bitmap_to_binary(to_bitmap(1))) |
+-------------------------------------+
| 0101000000 |
+-------------------------------------+
1 row in set (0.01 sec)
mysql> select hex(bitmap_to_binary(bitmap_empty()));
+---------------------------------------+
| hex(bitmap_to_binary(bitmap_empty())) |
+---------------------------------------+
| 00 |
+---------------------------------------+
1 row in set (0.01 sec)
Example 2: Convert each value in a BITMAP column into a binary string.
-
Create an Aggregate table
page_uv
where theAGGREGATE KEY
is (page_id
,visit_date
). This table contains a BITMAP columnvisit_users
whose values are to be aggregated.CREATE TABLE `page_uv`
(`page_id` INT NOT NULL,
`visit_date` datetime NOT NULL,
`visit_users` BITMAP BITMAP_UNION NOT NULL
) ENGINE=OLAP
AGGREGATE KEY(`page_id`, `visit_date`)
DISTRIBUTED BY HASH(`page_id`)
PROPERTIES (
"replication_num" = "3",
"storage_format" = "DEFAULT"
); -
Insert data into this table.
insert into page_uv values
(1, '2020-06-23 01:30:30', to_bitmap(13)),
(1, '2020-06-23 01:30:30', to_bitmap(23)),
(1, '2020-06-23 01:30:30', to_bitmap(33)),
(1, '2020-06-23 02:30:30', to_bitmap(13)),
(2, '2020-06-23 01:30:30', to_bitmap(23));
select * from page_uv order by page_id;
+---------+---------------------+-------------+
| page_id | visit_date | visit_users |
+---------+---------------------+-------------+
| 1 | 2020-06-23 01:30:30 | NULL |
| 1 | 2020-06-23 02:30:30 | NULL |
| 2 | 2020-06-23 01:30:30 | NULL |
+---------+---------------------+-------------+ -
Convert each value in the
visit_users
column into a binary-encoded string.mysql> select page_id, hex(bitmap_to_binary(visit_users)) from page_uv;
+---------+------------------------------------------------------------+
| page_id | hex(bitmap_to_binary(visit_users)) |
+---------+------------------------------------------------------------+
| 1 | 0A030000000D0000000000000017000000000000002100000000000000 |
| 1 | 010D000000 |
| 2 | 0117000000 |
+---------+------------------------------------------------------------+
3 rows in set (0.01 sec)