childrenOfIssuesInQueryRecursive not working with "custom_field is empty"

[Marco Sorich]

Dear community

I use "JQL Search Extensions" in the Jira Cloud.

With this I want to get all issues, whose parent (or parent-parent) has no "Esc Level" set. Where "Esc Level" is a custom field of dropdown type with the content "1", "2" and "3". My Jira project is a team managed project and "Esc Level" is a custom field inside this team managed project (in case this is relevant here).

When I execute the following query to search for all issues whose parent is of esc level 1, it works great:

issue in childrenOfIssuesInQueryRecursive("'Esc Level' = 1")

But when I execute the query to search for all issues whose parent has no esc level set yet, I get no results although I have such issues in my Jira:

issue in childrenOfIssuesInQueryRecursive("'Esc Level' IS EMPTY")

Is there any known restriction on the sub-query, which I can use inside of childrenOfIssuesInQueryRecursive()?

Regards
  Marco

[Marco Sorich · Accepted solution]

We found it already on our own.

Problem seemed to be a timeout that has occurred (or a too big amount of found issues in the sub-query). When I change the query to 

issue in childrenOfIssuesInQueryRecursive("project = xyz AND 'Esc Level' IS EMPTY")

it works fine now.