title: Bloated innodb datafile (ibdata1) and how to reclaim space?
body: <p>I have about 12GB of data in my tables and my datafile, ibdata1, used to be about 12GBs in size. I then ran the following command</p>
  
  <pre><code>alter table `rails_production`.`pictures` change `data` `image_file_data` mediumblob NULL
  </code></pre>
  
  <p>While it was making a temporary copy of the table, I got the following error</p>
  
  <pre><code>ERROR 1114 (HY000): The table '#sql-7fe4_12c9' is full
  </code></pre>
  
  <p>I assume this means there wasn't enough space to make a temporary copy of the table. But now the datafile is 17GB! How do I reclaim the space in the datafile?</p>
  
  <p>Is there a way to check how much of that 17GB is being used?</p>