On 05/05/2011 01:00 PM, Jim Nasby wrote:
> On May 4, 2011, at 6:24 PM, Andrew Dunstan wrote:
>> I'm far from convinced that storing deltas per column rather than per record is a win anyway. I don't have hard
numbersto hand, but my vague recollection is that my tests showed it to be a design that used more space.
> It depends on how many fields you're changing in one go and how wide the table is. It's also a PITA to identify what
fieldsactually changed if you're storing everything.
No it's not. Instead of storing OLD/NEW, store a base record and a delta
record (an hstore with just the changed fields) for an update. This
saves space and means you only have to calculate what changed once.
cheers
andrew