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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.

  1. Create an Aggregate table page_uv where the AGGREGATE KEY is (page_id, visit_date). This table contains a BITMAP column visit_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"
        );

  2. 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        |
      +---------+---------------------+-------------+

  3. 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)