How can I map multiple items from a code node to a Supabase array column without defaulting to the first item?

Below is a summary of how to resolve this issue:

What's Happening

When you reference a node output using the shorthand expression .item, n8n tries to determine a unique item from a previous node. When the previous node returns multiple items (or in your case, an array of arrays), n8n doesn’t know which one to pick and throws the "Can't determine which item to use" error.

The Recommended Approach

Instead of using .item or .first(), you can use the .all() method to access all the items from the previous node. For example, if your Code node is named “My Code Node”, you can reference its output like this:

JSCopied
{{ $("My Code Node").all() }}

This returns an array with all the items from that node—letting you map the entire array to a column in Supabase rather than just the first item.

Mapping the Entire Array to Supabase

In cases such as mapping a column in Supabase with the complete array—even if you have 40+ items—you should:

1. Ensure your Code node returns a single item with your array as a property. For example:

   JSCopied
   // In your Code node:
   return [
     {
       json: {
         arrayData: myArray // myArray could be your array of arrays
       }
     }
   ];

2. In your Supabase node, reference the entire array using the .all() method if you're pulling directly from another node, or use the property you set (in the above example, arrayData). For instance:

   JSCopied
   // If referencing the property from the node output directly:
   {{ $("My Code Node").first().json.arrayData }}

   Or if the previous node directly outputs an array of items (and you want to use them all) then handle that appropriately by ensuring your Supabase query expects and processes an array.

Additional Resources

There isn’t a single video tutorial on this exact situation, but you can find detailed guidance in the official documentation:

• The Item Linking Errors and Item Linking in the Code Node sections explain how to manage item linking and avoid related errors.
• More details on accessing output items from previous nodes (e.g. .first(), .last(), .all()) can be found in the Built in methods and variables | Output of other nodes documentation.

These resources provide practical examples and troubleshooting steps to help you handle multiple items effectively in your workflows.

By using .all() and/or restructuring your Code node output, you’ll be able to map your entire arrays without running into the ambiguity error.