CouchDB View - Filter by List Field Attribute (doc.objects.[0].attribute)

Question

I need to create a view that lists the values for an attribute of a doc field.

Sample Doc:

{
   "_id": "003e5a9742e04ce7a6791aa845405c17",
   "title", "testdoc",
   "samples": [
       {
           "confidence": "high",
           "handle": "joetest"
       }
   ]
}

Example using that doc, I want a view that will return the values for "handle"

I found this example with the heading - Get contents of an object with specific attributes e.g. doc.objects.[0].attribute. But when I fill in the attribute name, e.g. "handle" and replace doc.objects with doc.samples, I get no results:

Toggle line numbers
// map
function(doc) {
  for (var idx in doc.objects) {
    emit(doc.objects[idx], attribute)
  }
}

Ingo Radatz · Accepted Answer · 2015-04-14 18:05:58Z

2

That will create an array of key-value-pairs where the key is alway the value of handle. Replace null with a value you want e.g. doc.title. If you want to get the doc attached to every row use the query parameter ?include_docs=true while requesting the view.

// map
function (doc) {
  var samples = doc.samples
  for(var i = 0, sample; sample = samples[i++];) {
    emit(sample.handle, null)
  }
}

edited Apr 14, 2015 at 18:05

answered Apr 14, 2015 at 18:00

Ingo Radatz

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6 Comments

Ingo Radatz Over a year ago

Oh. I have misread your example doc. Samples is an array. I will update my answer.

Jon Reid Over a year ago

That's excellent, thank you llabball. Can I use a startkey with this setup or will I need to filter in my python app?

Ingo Radatz Over a year ago

The list is sorted be the keys. You can request a range with the query params ?startkey="..."&endkey="..."

Jon Reid Over a year ago

Awesome, thanks again llabball. In truth I'm using the results of this view as a base to find matches across records that have the same handle value in their sample lists. If there's a possibility of doing that in a view rather than in code, I can create another question and post the link.

Ingo Radatz Over a year ago

Yes, its possible to use a reduce step. Create a new question.

|

sebster · Accepted Answer · 2015-04-15 05:55:13Z

2

Like this ->

function(doc) { 
    for (var i in doc.samples) {
      emit(doc._id, doc.samples[i].handle)
    }   
}

It will produce a result based on the doc._id field as the key. Or, if you want your key to be based on the .handle field you reverse the parameters in emit so you can search by startKey=, endKey=.

edited Apr 15, 2015 at 5:55

answered Apr 14, 2015 at 18:04

sebster

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5 Comments

Ingo Radatz Over a year ago

^5 We ended with almost the same answer :-)

Jon Reid Over a year ago

Thanks sebster. I would accept both but I can't. I upvoted both instead.

sebster Over a year ago

Heh, yeah... well, it's not like we had to many ways to go about this. Actually wait, we had... with all the for types in javascript

sebster Over a year ago

@Jon Reid Thanks, but he was faster so his answer should be accepted anyway. Upvoting his answer as well.

sebster Over a year ago

This is how SO should be, mate :)

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