title: CONCAT string to longblog and mysql disk usage
body: <p>If I am an innodb table that this query executes a lot (once every second for some time with a small amount of data appended) and have <code>innodb_files_per_table = 0</code> can this cause a problem with storage? The blob itself could be 2-3MB but I lost 30gb of data usage and am wondering if this code is to blame in any way or if I should be looking somewhere else.</p>
  
  <p>SQL</p>
  
  <pre><code>UPDATE phppos_app_files 
  SET file_data = CONCAT(file_data, "NEW LINE OF DATA")
  WHERE file_id = 10;
  </code></pre>
  
  <p>Schema:</p>
  
  <pre><code>mysql&gt; show create table phppos_app_files;
  +------------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  | Table            | Create Table                                                                                                                                                                                                                                                                                                                                                                                                             |
  +------------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  | phppos_app_files | CREATE TABLE `phppos_app_files` (
    `file_id` int(10) NOT NULL AUTO_INCREMENT,
    `file_name` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
    `file_data` longblob NOT NULL,
    `timestamp` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    `expires` timestamp NULL DEFAULT NULL,
    PRIMARY KEY (`file_id`)
  ) ENGINE=InnoDB AUTO_INCREMENT=7577 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci |
  +------------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  1 row in set (0.00 sec)
  
  mysql&gt; 
  </code></pre>
  
  <p>The data stored in blog column is 2-3 mb of log text; just plain text. My question I am asking though is if frequent update queries where you concat from the current value cause storage issues where it causes huge problems with database. I just want to make sure it only stores the least amount of info and if an update with concat can cause any huge disk issues.</p>