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From Jan Lehnardt <...@apache.org>
Subject Re: Ad-hoc filtering
Date Tue, 26 Feb 2013 13:59:15 GMT

On Feb 26, 2013, at 14:54 , Troy Farrell <troy@entheossoft.com> wrote:

> It's probably not a popular opinion, but this application does not sound
> well-suited for CouchDB.  If you are creating views all the time, using
> them once and still downloading all the data for post-processing, then
> something is clearly wrong.  We may be able to help you restructure the
> data and views so you need fewer of them, but if you truly need lots of
> dynamic queries, CouchDB may not be the best choice for your application.
> (I would love for someone on this list to tell me I'm wrong.)

I think determining when CouchDB is *not* a good fit is crucial. I for one
am not interested in unhappy users.

Best
Jan
-- 


> 
> Troy
> 
> On Mon, Feb 25, 2013 at 5:50 PM, Daniel Gonzalez <gonvaled@gonvaled.com>wrote:
> 
>> Hi,
>> 
>> It is not possible for me to define and manage all possible views that my
>> application needs. Each time that I need to access data with a new
>> filtering mechanism I have to:
>> 
>>   1. Check if that view, or a similar one, already exists. (How would I
>>   call this if I had created this half a year ago?)
>>   2. If it doesn't, I must create it (javascript, not my piece of cake. I
>>   am most of the time in python land).
>>   3. I have to push the new design doc to all my servers (did you also
>>   push to that-server-that-you-never-use? Do you really need to push this
>>   view to that server? I don't remember, really.)
>>   4. I have to trigger the new view (which can take some time in databases
>>   with lots of docs), in all servers.
>> 
>> So now you need to filter for False instead of True? Great! Rinse and
>> repeat! At the end of the day I end up with dozens of views, some of them
>> outdated, which I am not using anymore, but I am unable to maintain.
>> 
>> Besides, defining lots of views becomes impractical: the more views you
>> have in a design doc, the longer it takes a refresh when the design doc is
>> modified. And the more views, the more space the database uses.
>> 
>> At some point this becomes very painful. Which means that for some data I
>> just do client-filtering.
>> 
>> Very often I must perform the following operations:
>> 
>>   1. Access a view
>>   2. Filter the documents in the view according to some criteria (which is
>>   not supported by a view)
>>   3. Paginate the resulting documents
>> 
>> Since the filtering is done in the client, I am forced to get all
>> documents. I will discard most of them, but since I do not know which ones,
>> I still must get them all. This is very slow.
>> 
>> Since for some data I do view-filtering, and for other data I do
>> client-filtering, some operations are taking a very long time to complete,
>> whereas others are completed very fast. Which is confusing for the user.
>> 
>> It would be great if couchdb supported field filtering. For example I would
>> pass a dictionary like this: { 'available' : true, 'user' : 'user1' } And I
>> would get only the documents which satisfy the filter. Using a single view.
>> A simple "is equal to" operation for the given fields would go a looong way
>> to solve most of my filtering needs.
>> 
>> The view engine would perform the standard indexing, and the filtering
>> would be an extra layer (slowing things down a bit, probably). It would be
>> a compromise between view indexing and client filtering.
>> 
>> Does this mechanism already exist? Does it make sense? Would it ever be
>> implemented?
>> 
>> Thanks
>> Daniel Gonzalez
>> 


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