InfoPath Dev

I am trying to query a SharePoint 2013 list from InfoPath 2013 WebForm. I took the reference from johnliu’s blog.
1. Created a Data connection “Rest_Equipments” to query the list using following filter
  http://MyURL /_vti_bin/listdata.svc/Equipment_No?$filter=Unit%20eq%20'UNIT00-EOH'
2. Created one more “list” data connection called “Units” to bring “Unit numbers” for lookup from SharePoint list
3. Created a Drop-Down List box “Unit Number” to show the available Unit numbers using Units data connection
4. On selection of “Unit Number” created following rule to change the Rest URL & query
  i. concat("http://MyURL/_vti_bin/listdata.svc/Equipment_No?$filter=Unit%20eq%20'", Unit Number, "'")
  ii. Query using data connection “Rest_Equipments”
5. Created a Drop-Down List box which is fetching “Equipment Number” from External data source “Rest_Equipments”, this should bring the result as per 4. -> i.
It works as expected in the InfoPath Designer preview, but it does not return any results after publishing & opening it in browser, and there is no error as well. Can someone point at what may be going wrong here?


Thanks in Advance

Interesting that there is no error - if the query failed to execute due to loopback check I'd expect an error. If you put the data fields from the secondary data source on the form so you can see them in the browser form, does any data get populated? What about getting rid of the %20 in your concat for your filter - I've never encoded spaces in a REST query before, perhaps try that...

Thanks for the insight Hilary, I have already disabled Loopback check, When I use data fields from secondary data source it works fine.
On selection of Unit number I am firing REST filter to get Equipment Numbers on the basis of Unit numbers (from 40,000+ Equipment Numbers).
I removed the %20 from the filter still same.

Well till not I was using small sample list & not filtering from actual 40000 records but when I tried filtering from the actual list it did gave me this error: "XML data that is required for this form to function correctly cannot be found." looks like loopback issue, but at the same time if I use same REST filter on the list with less data; it neither gives error nor any query result, I have no clue why !!!!

Maybe check your ULS logs - I wonder if the REST URL you are using would be displayed there & then you could try the same URL in the browser. Or put your same concat in a test field as the default value so you can put that on the form, copy out the URL & verify you get results in the browser?

I checked the ULS logs it looks like permission issue, as things are working as expected in the design preview!! . I could see following entries in ULS logs.

Name=Request (POST:http://MyURL/_layouts/15/Postback.FormServer.aspx) Non-OAuth request. IsAuthenticated=True, UserIdentityName=0#.w|pcl\96085, ClaimsCount=55 Entering monitored scope (Request (GET:http://MyURL/_vti_bin/listdata.svc/Equipment_No?$filter=Unit eq 'UNIT15-EP1')).

I pasted the REST from the logs in the browser it renders xml.

Though I have disabled the loopback check do you think I am missing out on anything else?