Facet on multi value field combined with sum of other field

Question

I have a similar solr scheme like this:

<doc>
    <str name="count">5</str>
    <arr name="tag_id">
        <str>1</str>
        <str>2</str>
    </arr>
</doc>
<doc>
    <str name="count">2</str>
    <arr name="tag_id">
        <str>2</str>
        <str>3</str>
    </arr>
</doc>

And as a result I am looking for the facets on tag_id combined with the sum of count like:

tag_id: sum
1: 5
2: 7
3: 2

Is there an easy solution with this? I stumpled upon function queries, but I am not sure if this is solvable with it.

Answer 1

Please check for Solr Pivots

Solr Pivot should be able to provide hierarchical facets, which you can use as facet.pivot = tag_id,count.

You should get back results as

tag_id 1
    count 5
tag id 2
    count 2
    count 5
tag id 3
    count 2

You can do the count consolidation on the client side.