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From Jan Lehnardt <>
Subject Re: Replicating a subset of data(data for user of a website)
Date Mon, 29 Mar 2010 06:19:18 GMT
Hi Audrey,

CouchDB is well suited for your needs :)

There are two approaches you can take:

1) Create a database per user (or itinerary). That way,
replicating a database will only include the data that's
interesting to a single user. On the server side, you
don't end up with a ginormous database that has all
users' data mashed together.

2) If you like ginormous databases, you can use a new
technique called "filtered replication" that lets you replicate
only a subset to your users netbooks. It is described in more
detail on the Couchio blog*. Note that this is only available
in CouchDB 0.11.0 which is about to be released.


3) Bonus version: For completeness sake, there is another
possible approach that might work as a stop-gap but is not,
I think feasible. You can define a document update validation
function on your users' netbooks to block all writes that include
data they are not interested in. If you replicate now, the netbook
will only include the user's data, but for each client you will send
all your data down and the client's CouchDB rejects the writes.
Like I said, very likely not feasible in your case.

I'd go with 1) if you don't need the big database and 2) if you do.


On 28 Mar 2010, at 22:41, Audrey Lee wrote:

> Hello List,
> I'm starting work on a website for tourists.
> The basic use-case is that a tourist uses the site to store and
> retrieve information about itineraries.
> In addition to the website I want to create a netbook application
> which the tourist can use while she is disconnected from the web.
> I want the netbook application-data-store to synchronize with the
> data-store of the website.
> The replication abilities of couchDB interest me.
> I'm curious about some deployment issues.
> How easy is it to implement couchDB such that all of the data for all
> of the tourists is in a data-center?
> Obviously I want each tourist to have a local copy of only her data.
> Is it easy to deploy couchDB on each netbook so the netbook has only
> data related to 1 user?
> Based on the small amount of reading that I've done, I gather that it
> is easy to replicate an entire couchDB between hosts.
> For my use case, I dont want to replicate an entire couchDB from a
> data-center to a netbook.
> Instead I want to replicate a subset of a couchDB.
> Has anyone on this list dealt with a use-case similar to my
> tourist-site-and-app use-case?
> --Audrey

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