title: Is it possible to alter a record in rails, without first reading it
body: <p>I want to alter a record, but I don't want to read it out of the database first, because frankly I don't see the point. It's huge and across a network that is slow and expensive.
  Can it be done (easily)?</p>
  
  <p>Lets say I have a record with 100 fields (for arguments sake) and I want to alter one field in the table.  I have a really bad connection to the database (this is true) because it's housed on a different box and there's nothing I can do to change this.
  Right now I pull down the record and rails validates its contents (because I have serialized bits) I then alter one field (one of the hundred depending on X condition) and save the record again. Which I suppose writes the whole record to the database again, with no knowledge of the fact that I only changed one small bit. <em>(this last bit is assumption)</em></p>
  
  <p>Now to change one record it's sending a huge amount of data across the network, and it could be that I'm only changing one small small thing.. 
  Also it's doing two queries on the database. First the select * then the update.. </p>
  
  <p>So my question.. are there smarter base classes that do this right, to write without read?<br>
  Top of my head I would think a setter method for each field with a bool flag for changed. 
  When saving, walk the flags and where true...  Does this happen now, if so how do I make use of it?</p>