Process Variable not getting assigned with DSE

Question

I have a rule to fetch DSE from database. Debugged and works fine. 
 In my process model, I'm using pkId to lookup data using my rule and then assigning it to a process variable. Unfortunately my process variable is not getting assigned. When I debug the process, I don't see any errors and I've double checked my rule for fetching data and that I'm passing id correctly. 
 On the Data Output tab of my script task I'm calling the rule - rule!GetDataById(pv!myId) with a Custom Output. myId is populated with value e.g. 4, and I see it when I debug 
 I'm storing the results in process variable for my entity. However, after I let the script task finish and check my process variables, my entity object is empty. 
 This should just work :-( 
 What obvious thing could I be missing?

Mike Schmitt · Accepted Answer

BTW, when you post code, you should consider using a Code Box , by hitting "Insert" -> "Insert Code". This will preserve formatting/indenation, and give a nice size-constricted display box to keep the comment from wasting an undue amount of space within the conversation. 
 For instance, here's the same code as above, except I've added the filter value (and set the applyWhen parameter as well). I used "ri!inputId" but you can use whatever your rule input is called. 
 a!queryEntity(
 entity: cons!VEHICLE_DSE_VFM,
 query: a!query(
 logicalExpression: a!queryLogicalExpression(
 operator: "AND",
 filters: {
 a!queryFilter(
 field: "id",
 operator: "=",
 value: ri!inputId,
 applyWhen: not(isnull(ri!inputId))
 )
 },
 ignoreFiltersWithEmptyValues: true
 ),
 pagingInfo: a!pagingInfo(
 startIndex: 1,
 batchSize: 50
 )
 ),
 fetchTotalCount: false
) 
 Edited to add: I also notice you're not referencing the ".data" of the rule's dataSubset output (as I suspected earlier, which is why I was asking you to post the sample output of this rule to confirm). So, before you can expect get any data properly saving into your in-process PV, you will need to add ".data" either within the expression rule (at the very end of the a!queryEntity() call), or in the process model itself after the expression rule call. I.E., 
 rule!VFM_getVehicleById(inputId: pv!updateId).data

Mike Schmitt · Answer

Sorry, then I misunderstood what you were referring to when you said your PV was "data store entity" type. 
 Can you confirm / post a screenshot of the output of rule!VFM_getVehicleById() when passing in an example id, within the expression rule editor? For example, sometimes people forget to reference the ".data" in the query entity output, to get the CDT type data itself as opposed to the DataSubset returned by default by a!queryEntity.

Mike Schmitt · Answer

appianfreak said: Is there a way to debug/trap data returned from the fetch rule *before* Appian populates it into vehicle pv? 
 Yes - as I said before, open VFM_getVehicleById in the Expression Rule editor , enter your id input (4), and click "Test Rule". Have you done this already? And if so, what is the exact result? 
 If you want to "trap" the rule's output within the process model only (i.e. you think it's already working when viewed from the expression rule editor), you can create a new (temporary) TEXT PV, and save the same query result (wrapped in the toString() function) into it. This will generally tell you whether any data at all is being returned from the query when the process is run, for instance if it's something that's returning data but not matching the CDT type of the original target PV.

Mike Schmitt · Answer

To get the data from the data subset, you add ".data" either after the query entity expression, or after the expression rule where you call it. Note that I talked about this and also put it into one of my more recent code examples above. 
 Appian doesn't give an error because it freely allows types to be cast as other types, and it has no inherent way of knowing whether you're trying to do a valid typecasting or not.

Mike Schmitt · Answer

Not sure what to tell ya then. Type casting will attempt to work between any two complex types as far as I know and will use any fields named the same. Particularly because it would let me cast a type containing "name", "id" and a hundred other fields, for example into a special CDT containing just "name" and "id". But if there are no common properties between the two types, then the resulting cast operation will result in blank data, such as what you were seeing.

Process Variable not getting assigned with DSE

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