How to filter query based on two input parameters

Looking at the screenshot below we see that a User can participate in one or more rounds, and a round can (will) have many Users, and both will link to many EvaluationEvents. A EvaluationEvents must link to both User and Round.


I want to query all the EvaluationEvents and ConceptItems for a single User and single Round. I don’t know how to use both input parameters in a single select (I think this would be preferred), so I made a failed attempt to create two SELECTs and use an INTERSECT. Below shows working code for the two selects and I remmed code used for the intersect.

  1. What’s better, use both param in a single SELECT
  2. Two SELECTs and in INTERSECT
    Which every you choose, can you kindly please show me how?

CREATE QUERY GetUserRndEvals(vertex<User> usr, vertex<Round> rnd) FOR GRAPH MyGraph syntax v2 { 
  startUser = {usr};
	startRound = {rnd};
  Items = Select tItm FROM startUser:s-(User2EvaluationEvent>:eUserEvent)-EvaluationEvent:tEvent-(EvaluationEvent2ConceptItem>:eEvItm)-ConceptItem:tItm
	ACCUM @@edgeEvents += eEvItm; #, @@vertEvents+=tEvent;
	#2nd SELECT for the intersect
	Events = SELECT tEvent FROM startRound:s-(Round2EvaluationEvent>:eRndEvent)-EvaluationEvent:tEvent;
	#@@intersectEvents = Events INTERSECT @@vertEvents;	
	Print Items;
	Print @@edgeEvents;
	#Print @@vertEvents;

Thank You!

There are a few ways of doing this. The most intuitive way is to first get the EvaluationEvent you want, then go on from there. There isn’t a way I can think of to do this in a single path, and we can’t match on an intermediate set (though there is a lot of thinking going on for this as I believe Neo can do this, and we aim to please) .

Anyway, here’s my first thinking. I haven’t tested it so apologies if it has any mistakes, hopefully it will still make sense.

Note the need for a reverse edge between Round2EvaluationEvent, given you have defined it as directed according to the diagram above.


myTE = select tEvent from startUser -(User2EvaluationEvent>)-EvaluationEvent:tEvent;
myTE = select tEvent from EvaluationEvent:tEvent-(rev_Round2EvaluationEvent>)-Round:r
WHERE r == rnd; // filter on parameter

// Now you've got the filtered EvaluationEvent

Items = Select tItm FROM myTE:tEvent-(EvaluationEvent2ConceptItem:eEvItm>)-ConceptItem:tItm
ACCUM @@edgeEvents += eEvItm; #, @@vertEvents+=tEvent;

Hi Richard,
Thank you. This will probably take a few more iterations since you don’t have access to the graph.

  1. How did you know it was a directed edge? I changed it to a reverse edge and it still has the same appearance.

  2. Was this an oversight? “myTE” is not used in the 2nd SELECT and is overwritten in the 2nd SELECT?

  3. And this is the compile error shown in the screenshot above:

(10, 72) Error: no viable alternative at input ‘myTE:tEvent-(EvaluationEvent2ConceptItem:eEvItm>’
(10, 86) Error: mismatched input ‘:’ expecting {INTERSECT, MINUS, UNION, ‘%’, ‘&’, ‘+’, ‘-’, ‘*’, ‘/’, ‘.’, ‘;’, ‘>’, ‘|’, ‘<<’}

  1. And the is the 2nd of 2 compile errors (neither of which make sense to me):

(6, 21) Error: unsatisfiable FROM pattern, query result always empty

(6, 48) Warning: unsatisfiable pattern -(Round2EvaluationEvent>)-Round:r
(6, 48) Warning: unsatisfiable pattern -(Round2EvaluationEvent>)-Round:r
(6, 26) Warning: unsatisfiable pattern EvaluationEvent:tEvent-(Round2EvaluationEvent>)-Round:r

Do you have further recommendations?

Thanks again.

  1. I kinda assumed. The arrow tells me it was directed. So the only way to go backwards is via the reverse edge.

  2. I’m deliberately over-writing it, but there is an error, I think.

  3. OK. that second line should say (I think):
    myTE = select tEvent from myTE:tEvent-(rev_Round2EvaluationEvent>)-Round:r WHERE r == rnd; // filter on parameter

OK that makes more sense to me, which brings us to this screenshot:

(9, 21) Error: unsatisfiable FROM pattern, query result always empty

(9, 37) Warning: unsatisfiable pattern -(Round2EvaluationEvent>)-Round:r
(9, 37) Warning: unsatisfiable pattern -(Round2EvaluationEvent>)-Round:r
(9, 26) Warning: unsatisfiable pattern myTE:tEvent-(Round2EvaluationEvent>)-Round:r

Shouldn’t that be a reverse edge? I’m guessing (reverse_Round2EvaluationEvent>) maybe?


You have been using some prefixes such as “reverse_”. Is that an actual prefix recognized by TG, or is it more like a comment to let me know what edge type it should be?

So there are a bunch of concepts here. Firstly, I recommend you go through the 101 training if you haven’t already:

Directed edges can be defined in the schema to have both the forward and reverse edges. If you use graph studio then you can simply tick a checkbox to get the reverse edge. By convention, graph studio names the reverse edge by prefixing the edge name with “reverse_”.

If you define the schema explicitly (on the command line) then you can name the reverse edge anything you like.

When traversing the path, if you are going backwards along a directed edge then you explicitly need a reverse edge. If you don’t, then the code parser will usually spot the error as you have seen.

You gave the screenshot, which had the relevant clues:

Note here the reverse edge is explicitly named, and that’s the one you need in your code to get from EvaluationEvent back to Round. OK?

OK Thank you and I think we’re getting close. Hopefully this is the last error (everything looks good to me):

(14, 53) Error: no viable alternative at input ‘myTE:tEvent-(EvaluationEvent2ConceptItem:eEvItm>’

(14, 67) Error: mismatched input ‘:’ expecting {INTERSECT, MINUS, UNION, ‘%’, ‘&’, ‘+’, ‘-’, ‘*’, ‘/’, ‘.’, ‘;’, ‘>’, ‘|’, ‘<<’}

and this is the edge used in the last “From” clause:


No need for a reverse edge here right? as an EvaluationEven “has” ConceptItems.

and here’s the query text:

CREATE QUERY GetUserRndEvals3(vertex usr, vertex rnd) FOR GRAPH MyGraph syntax v2 {


myTE = Select tEvent From startUser -(User2EvaluationEvent>)-EvaluationEvent:tEvent;

myTE =
Select tEvent from myTE:tEvent-(reverse_Round2EvaluationEvent>)-Round:r
Where r == rnd; // filter on parameter

// Now you’ve got the filtered EvaluationEvent
Items =
Select tItm
From myTE:tEvent-(EvaluationEvent2ConceptItem:eEvItm>)-ConceptItem:tItm
Accum @@edgeEvents += eEvItm;

Print myTE;
Print Items;
Print @@edgeEvents;


Thank you.

I think you’ve just got the right caret in the wrong place, it needs to be before the colon:


That was it. Thank you for staying with this and it’s now making sense to me.