title: how to use single core for each collection in solr cloud?
body: <p>Is there any way in solr cloud to keep one collection's data in place so that all indexing and search queries are triggered to that collection only. I am facing an issue in solr join queries.
  lets say I have a document,</p>
  
  <pre><code>{
          "form_object_id":"a5ec120cd61e41a2a8f05b01edbb8a89",
          "app_id":2400,
          "id":"formobj_a5ec120cd61e41a2a8f05b01edbb8a89_account_1704",
          "account_id":1704,
          "location_gps_value":"[]",
          "title":"Mumbai",
          "formobject_created_at":"2019-03-31T09:28:40Z",
          "formobject_id":"a5ec120cd61e41a2a8f05b01edbb8a89",
          "Region_2_name":["Maharashtra"],
          "Region_2":["a478ce4bcd7c441c8534849631bebaf8"],
  }
  
  
  In this document i have one field "Region_2" which contains one id "a478ce4bcd7c441c8534849631bebaf8" &amp; this id is present in 208 other solr documents like,
  
  {
          "form_id":26825,
          "form_object_id":"a478ce4bcd7c441c8534849631bebaf8",
          "title":"Maharashtra",
          "location.lat":0.0,
          "location.long":0.0,
          "created_date":"2019-03-31T09:27:55Z",
          "form_name":"Region",
          "type":"assetformobject",
          "id":"formobj_a478ce4bcd7c441c8534849631bebaf8_account_1704",
  }
  </code></pre>
  
  <p>here form_object_id is same as that as "Region_2" field in previous documents.
  when i join like,</p>
  
  <pre><code>{!join+from=Region_2+to=form_object_id}title:Mumbai
  </code></pre>
  
  <p>this query was supposed to return 208 documents but its return only 51 but when i started solr in single core same query return's all 208 results.
  I think this may be because solr distribute documents across multiple shards.
  Is there any way to do this in solr cloud?</p>