Compare Datasets does not return an empty item with “Always Output Data” enabled

Questions
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1

I’m having trouble counting the “Different” elements produced by the Compare Datasets node.

What I’m trying to do: My project fetches an online XML file and compares it with the previously fetched version. Depending on whether differences exist, I want the workflow to take different actions.

What works: The fetching and comparison steps run correctly. The issue is with the empty output.

The problem: When the two XML files contain identical values, the “Different” output returns nothing, even though “Always Output Data” is enabled…. I expected it to return an empty array, which I could then pass into the “Count New Elements” node. An empty array should result in a count of 0, which would feed into the IF node.

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Instead, the “Count New elements” node receives no input, there is nothing I can drag and drop into the “Fields to summarize/Field” section, even when I connect the “In A only” output.

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What am I doing wrong here?

Information on your n8n setup

  • n8n version: 1.123.5
  • Database (default: SQLite): SQLite
  • n8n EXECUTIONS_PROCESS setting (default: own, main): don’t know
  • Running n8n via: n8n cloud
  • Operating system: Windows
2

That’s a hard one, because that might be the expected behavior of this node.

What you can try, though, is to use the Merge node with a custom SQL string.

I tried to paste the workflow here, but there seems to be a bug when I paste SQL queries.