On 6 Mar 2009, at 20:24, aju wrote:
Jason Smith wrote:
aju wrote:
in a RDBMS when you update an existing row (document) it is a
single step. (there's no revision term here obviously). likewise
in subversion when you commit an updated document it is a single
step.
Well in a RDBMS if you have a common constraint like uniqueness on
a column, you have to decide whether to INSERT or UPDATE. So most
likely, you will grab a big lock, SELECT something, process the
data, INSERT or UPDATE, then release the lock. So that's two
queries as well.
you are right. probably bad example, but i still can't see the
argument
for not just updating a document based on the latest revision. how
can it hurt?
hmm, or perhaps instead one could specify a special rev value "latest"
PUT /somedatabase/some_doc_id?rev=latest
Imagine Wikipedia. You open a page for editing and sit down and write
a nice and well-researched paragraph about your favourite band. A
minute before you are done, I open the same page for editing, having
the same base version that you have. Now you save your page and submit
your work to Wikipedia. Then I save my changes to the version I know
is previous, but doesn't include your changes. My change gets saved
and yours is gone. Using _rev's I can't save my changes unless I get a
newer version with your changes.
For the record: CouchDB does not store diffs.
Cheers
Jan
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