Best design approach to query documents for 'labels'

Question

I am storing documents - and each document has a collection of 'labels' - like this. Labels are user defined, and could be any plain text.

{
  "FeedOwner": "4ca44f7d-b3e0-4831-b0c7-59fd9e5bd30d",
  "MessageBody": "blablabla",
  "Labels": [
    {
      "IsUser": false,
      "Text": "Mine"
    },
    {
      "IsUser": false,
      "Text": "Incomplete"
    }
  ],
  "CreationDate": "2012-04-30T15:35:20.8588704"
}

I need to allow the user to query for any combination of labels, i.e.

"Mine" OR "Incomplete"
"Incomplete" only
or
"Mine" AND NOT "Incomplete"

This results in Raven queries like this:

Query: (FeedOwner:25eb541c\-b04a\-4f08\-b468\-65714f259ac2) AND (Labels,
Text:Mine) AND (Labels,Text:Incomplete)

I realise that Raven will generate a 'dynamic index' for queries it has not seen before. I can see with this, this could result in a lot of indexes.

What would be the best approach to achieving this functionality with Raven?

[EDIT]

This is my Linq, but I get an error from Raven "All is not supported"

var result = from candidateAnnouncement in session.Query<FeedAnnouncement>()
where listOfRequiredLabels.All(
    requiredLabel => candidateAnnouncement.Labels.Any(
        candidateLabel => candidateLabel.Text == requiredLabel))
select candidateAnnouncement;

[EDIT]

I had a similar question, and the answer for that resolved both questions: Raven query returns 0 results for collection contains

Note that RavenDB creates dynamic indexes based on the query fields, not the values. In other words, you will always have a single index serving this query — Ayende Rahien
Thanks Ayende: A user could specify any number of labels, so would I end up with 1 index testing the labels against 1 literal value, another index for 2 literal values, another for 3, and so on? — Adam
Yes, that's the way it works. You will end up with one index having a lucene-document for each of your labels. Any number that your users specify will be tested against that one index. — Daniel Lang

Daniel Lang Daniel Lang · Accepted Answer · 2012-04-30T07:32:42

Please notice that in case of FeedOwner being a unique property of your documents the query doesn't make a lot of sense at all. In that case, you should do it on the client using standard linq to objects.

Now, given that FeedOwner is not something unique, your query is basically correct. However, depending on what you actually want to return, you may need to create a static index instead:

If you're using the dynamically generated indexes, then you will always get the documents as the return value and you can't get the particular labels which matched the query. If this is ok for you, then just go with that approach and let the query optimizer do its job (only if you have really a lot of documents build the index upfront).

In the other case, where you want to use the actual labels as the query result, you have to build a simple map index upfront which covers the fields you want to query upon, in your sample this would be FeedOwner and Text of every label. You will have to use FieldStorage.Yes on the fields you want to return from a query, so enable that on the Text property of your labels. However, there's no need to do so with the FeedOwner property, because it is part of the actual document which raven will give you as part of any query results. Please refer to ravens documentation to see how you can build a static index and use field storage.

Best design approach to query documents for 'labels'

1 Answers