On Oct 15, 2009, at 10:28 AM, Matt Goodall wrote:
Hi,
I think this is more of a dev question given that it needs some
knowledge of the deterministic rev algorithm ...
I was just wondering if CouchDB could use the deterministic rev stuff
to avoid writing changes to the database if nothing has actually
changed in the doc that is PUT back (or bulk updated, of course).
The most obvious use case is that it's horrifyingly common for users
to click an HTML form's submit button, instead of using the back
button, when they haven't changed anything. I suspect most
applications do not check if the user made any changes and therefore
end up sending exactly the same data back as an update ...
unnecessarily creating a new document rev, growing the database,
invalidating views, and triggering _changes updates.
CouchDB obviously has to calculate the hash for the new rev anyway, so
perhaps it could compare the new value to the current value, skip it
if it's unchanged and return the current _rev in the response.
Is that feasible? If so, I'll create a ticket for it.
- Matt
Hi Matt, it would easily be possible except for the fact that the old
revision of the document is part of the content used to generate the
hash that becomes the new revision. So even if the body didn't
change, the hash won't match the old rev.
I think it would be a nice improvement, and I honestly don't remember
off the top of my head the argument _why_ the old revision had to be
included. So yeah, a JIRA ticket seems like a good idea. Best,
Adam
