Detecting empty message produced by "SQL no rows"

[pinebit]

Hello!

I have sql_select => unarchive flow, and if my SQL query returns no rows by design, then I am getting a failure for "unarchive" task, because of empty message.
How shall I handle this case properly? I usually want to execute a fallback processor that would be run only if the query returned no rows.
Also, I would like that my "unarchive" task do not yield any errors. That is, I probably need to be able to test for empty message before even executing "unarchive" task. But I don't want to just drop/delete that empty message and instead execute another processor, such as "metric" to count such events.

Thank you!

[mihaitodor]

Hey @pinebit! I think you can leverage the switch processor for that purpose. The examples section should help you see how to use it, but you can basically leverage the bloblang length() method in the check field to determine if you have an empty message and then execute your metric processor under it.

[pinebit]

Thank you @mihaitodor

[pinebit]

I ended up doing this:

    - switch:
        - check: (this | "").length() == 0

without coalescing this.length() yields error:

Failed to test case 0: failed assignment (line 1): unable to reference message as structured (with 'this'): message is empty

Is this correct?

[mihaitodor]

Yep, that works. However, you can use content() instead of (this | ""), since that will be cleaner (and faster)