Issue counting nodes or relationships when count is 0

[krancour]

Hi all,

Having a bit of an issue with Spring Datagraph.

Given the following:

@NodeEntity
User {
  
  // ...

  @Query("start user=(%start) match (user)-[:MADE_DONATION]->() return count(*)")
  private int totalDonations;

  public int getTotalDonations() {
    return totalDonations;
  }

  // ...

}

I get the following when invoking getTotalDonations() IF the user doesn't HAVE any such relationships.

java.lang.IllegalStateException: Expected at least one result, got none.

This seems wrong. Shouldn't I get back 0? Is there a better way to do what I'm trying to do?

Any help is appreciated.

[MichaelHunger]

Which version of SDN are you using?

You should probably use optional relationships:

start user=(%start) match (user)-[?:MADE_DONATION]->() return count(*)

HTH
Michael

[andres.taylor]

You are right that optional is the key, but your query will never return anything less than one. You should use this instead:

start user=(%start) match (user)-[r?:MADE_DONATION]->() return count(r)

"COUNT(<identifier>), ... counts the number of non-null values in <identifier>", while count(*) returns the number of matching subgraphs, which is always at least one.