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From Bernd Grolig <>
Subject Best case for 1:many relation in CouchDB
Date Mon, 20 May 2013 16:29:08 GMT

I just started to set up an mobile App using TouchDB. It's the first time
for me to work with a NoSQL Database. While setting up the basics so far
worked very well, I stepped deeper in how to design the data structure of
the app.

The principle question for me is, what is the best design for 1:many
relations and for grouping.

I researched quite a lot in the web, but I am stil not sure, how to design
it in the best way. Would be great to get some hints from this mailing list.

So this is the basic data structure:

Document type: Categories

   "_id": "a124",
   "_rev": "8-089da95f148b446bd3b33a3182de709f",
   "detCat": "1st Category",
   "mainCat": "Main Category",
   "mainBereich": "Division",
   "type": "Transaction"

   "_id": "a125",
   "_rev": "3-089da95f148b446bd3b33a3182de232",

   "detCat": "2nd Category",
   "mainCat": "Main Category",
   "mainBereich": "Division",
   "type": "Transaction"


Document type: Transaction

   "_id": "7568a6de86e5e7c6de0535d025069084",
   "_rev": "2-501cd4eaf5f4dc56e906ea9f7ac05865",
   "Value": 133.23,
   "Sender": "Sender Name",
   "Booking Date": "11.02.2013",
   "Detail": "Some Transaction details",
   "catID": "a124"

   "_id": "23982304201948231213",
   "_rev": "2-234123412342",
   "Value": 199.23,
   "Sender": "Sender Name",
   "Booking Date": "11.04.2013",
   "Detail": "Some Transaction details",
   "catID": "a125"

As long as I want to receive all transactions with its correlating category
it is quite easy by using "include_docs=true" in the search string.

But as soon as I want to have a reduce or grouping e.g. to "MainCat" or to
"Division" I could not find a good solution to solve this.

My question is, if there is a possibility to generate a map/reduce view to
group to Main Cat or Division and sum all the transactions to this level?

The only possibility I see is to put the Category names and Main Category
Names and Division Names inside the document type of the transaction. But
this would cause a lot of work for updates when the name of a category is

The other possibility would be to get the result without reduce and sum
within the application logic, but this seems also not to be the very
elegant way.

I think this is a very basic design question and used many times in the
web, e.g. Tagging. However all examples I found only wrote the name of the
tag or in my case category in the document itself.
I'm curious to get some hints to solve this questions.

Best regards,

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