Dumping enormous MYISAM table with BLOB based on WHERE clause

[Ifechukwukwu Okobi]

Hi All,

I have a database with a MyISAM table of over 500GB in size.
The table has blob columns as can be seen below;

+----------------+--------------+------+-----+------------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------------+--------------+------+-----+------------+-------+
| id | varchar(50) | NO | PRI | | |
| filename | varchar(255) | YES | | NULL | |
| previewfile | longblob | YES | | NULL | |
| binaryfile | longblob | YES | | NULL | |
| list_id | varchar(50) | NO | PRI | | |
| preview_exists | tinyint(1) | YES | | 0 | |
| serve_date | date | NO | | 0000-00-00 | |
+----------------+--------------+------+-----+------------+-------+

Due to the current size and space restriction, I need to dump only this month data and drop the table before importing the data back.
I have tried using the command below but it takes forever to begin the dump.

mysqldump --databases content --skip-triggers --compact --no-create-info --single-transaction --tables upload_table --where="serve_date>= '2015-01-01'" > /backup/table_dump.sql

Please is there a faster way to do this and regain space or am I doing something wrong?

Thanks.