Best way to add column to a big table with longblob - mysql

Question

I have the following table:
CREATE TABLE IF NOT EXISTS PDF_STORAGE (
ID_PDF_STORAGE bigint(20) NOT NULL AUTO_INCREMENT,
DESC_FILE varchar(255) DEFAULT NULL,
PDF_FILE longblob,
LINK_FILE varchar(255) DEFAULT NULL,
VERSION int(11) NOT NULL DEFAULT '0',
PRIMARY KEY (ID_PDF_STORAGE)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;
Where PDF_FILE is a file of 10 MB on average. Today it has about 50.000 rows. I need to add a new column to this table but it is taking a long time, more than 10 min, some times giving a 401 error in PhpMyAdmin, so I'd like to know what is the proper way to achieve this...
I already tried:
ALTER TABLE PDF_STORAGE ADD VERSION INT NOT NULL DEFAULT '0' AFTER LINK_FILE ;
and
SET FOREIGN_KEY_CHECKS=0;
CREATE TABLE PDF_STORAGE_new LIKE PDF_STORAGE;
ALTER TABLE PDF_STORAGE_new ADD VERSION INT NOT NULL DEFAULT '0' AFTER LINK_FILE ;
INSERT INTO PDF_STORAGE_new (PDF_STORAGE, DESC_FILE, ID_PDF_STORAGE, LINK_FILE) SELECT * FROM PDF_STORAGE;
RENAME TABLE PDF_STORAGE TO PDF_STORAGE_old, PDF_STORAGE_new TO PDF_STORAGE;
DROP TABLE PDF_STORAGE_old;
SET FOREIGN_KEY_CHECKS = 1;
but they are also slow.. is there a better way?
Thanks

Answer 1

What you are doing now ALTER TABLE is the best approach to my knowledge. You can try making this change when there is not much transaction (or) DB operation going on. I mean say, do the changes in idle time.
ALTER TABLE PDF_STORAGE ADD VERSION INT NOT NULL DEFAULT '0' AFTER LINK_FILE ;
You can as well create a new table same as this table schema along with the new column.
Insert all the records from this table to the newly created table.
Rename the new table to the old table name.
delete the old table.