Grouping documents by a field in child documents in Solr

[Hima Bindu]

Hi,

    I have a requirement to group my results based on a field in child document.
Eg: In below documents, I need to group based on field “title” in child 
documents. 
My results should have list of parent documents and each parent document should 
have child documents grouped by their title.
I didn’t find a way to group child documents in solr documentation. Can any one 
help me with a solution for this?

[
{
    "ID": “1",
    "title": “new customers",
    "content_type": "parentDocument",
    "_childDocuments_": [
        {
        "ID": “2”,
        “title": “MD”,
        "comments": "Lots of new services”,
        "_nest_parent_”:”1"
      } {
        "ID": “3”,
        “title": “OD”,
        "comments": "Lots of new patients”,
        "_nest_parent_”:”1"

      }
    ]
  }
{
    "ID": “4",
    "title": “new customers",
    "content_type": "parentDocument",
    "_childDocuments_": [
        {
        "ID": “5”,
        “title": “MD”,
        "comments": "Lots of new services”,
        "_nest_parent_”:”4”
      } {
        "ID": “6”,
        “title": “OD”,
        "comments": "Lots of new patients”,
        "_nest_parent_”:”4"
      }
    ]
  }


]


Appreciate your help in advance!

Thanks, 
hpotla