Combining a query in Elasticsearch

Use bool query inside has_child.

curl -XGET "http://localhost:9200/my_index/my_type/_search?pretty=true" -d'
{
"query": {
  "bool": {
     "must": [
        {
           "query_string": {
              "default_field": "body",
              "query": "hello stackoverflow"
           }
        },
        {
           "terms": {
              "_id": [
                 "10"
              ]
           }
        },
        {
           "has_child": {
              "type": "user_item_relation",
              "query": {
                 "bool": {
                    "must": [
                       {
                          "term": {
                             "user_id": "1234"
                          }
                       },
                       {
                          "term": {
                             "fav": "0"
                          }
                       }
                    ]
                 }
              }
           }
        }
     ]
    }
  }
 }'