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From Eric B <>
Subject Re: How to store the delta between doc revisions?
Date Wed, 01 Oct 2014 19:18:09 GMT
Thanks for the valid points.  But either way (whether through patches or
storing the full previous revision), is there a mechanism in CouchDB in
which I can require all calls to trigger an updateHandler?  In a way, I'm
looking more for an update interceptor; something to be run just before a
document is actually persisted to the DB, but that is always executed.



On Wed, Oct 1, 2014 at 3:03 PM, Alexander Shorin <> wrote:

> Storing patches is good until you're in sure that no single patch will
> get suddenly deleted. Otherwise you could easily find all your history
> broken. Oblivious, but it is the thing to remember when picking this
> way of history management. Storing full document copies per revision
> is more solid solution for such case: you can easily skip or lose one
> or several revisions and be fine, but it also consumes much more disk
> space. Trade offs are everywhere, pick up the one that suites you.
> --
> ,,,^..^,,,
> On Wed, Oct 1, 2014 at 10:02 PM, Eric B <> wrote:
> > I'm new to CouchDB and trying to figure out the best way to store a
> history
> > of changes for a document.
> >
> > Originally, I was thinking the thing that makes the most sense is to use
> > the update function of CouchDB but not entirely sure if I can.  Is there
> > someway to use the update function and modify/create a second document in
> > the process?
> >
> > For example, if I have a document which contains notes for a client.
> > Everytime I modify the notes document (ie: add new lines or delete
> lines),
> > I want to maintain the changes made to it.  If there was a way to use
> > CouchDB's rev fields for this, my problem would be solved, but since
> > CouchDB deletes non-current revs upon compaction, that is not an option.
> >
> > So instead, I want to create a "history_log" document, where I can just
> > store the delta between documents (as a patch, for example).
> >
> > In order to do this, I need to have my existing document, my new
> document,
> > compare the changes and write them to a history_log document.  But I
> don't
> > see if/where I can do that within and update handler.
> >
> > Is there something that can help me do this easily within CouchDB?  Are
> > there patch or json compare functions I can have access to from within a
> > CouchDB handler?
> >
> > Thanks,
> >
> > Eric

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