Why does my Firestore onDocumentCreated trigger also fire for partial_ingredients events?

Below is one likely explanation and approach to address the issue.

Why Are You Receiving Extra Events?

Even though you specified a trigger for documents created at path

  course/{courseID}

if you are also writing documents in a collection called partial_ingredients or in a subcollection (for example, course/{courseID}/partial_ingredients/{docId}), those writes may be firing additional events for a function that isn’t meant to receive them. In other words, the function’s path must exactly match the documents you care about. If your partial documents are stored in a different collection or subcollection, make sure you’re not “listening” to those document paths by mistake.

How to Fix It

1. Verify Your Paths:
   Double-check that the course documents are really in the collection “course” and that the partial ingredients aren’t inadvertently being written to that same top‑level collection. If the partial ingredients are in a subcollection (for example, course/{courseID}/partial_ingredients), they will not trigger a trigger defined on course/{courseID} (unless you have another function or an incorrect path).

2. Use Separate Triggers:
   If you want to process only course documents, define the trigger exclusively on that collection. For example, if your course documents live in “course” and your partials are in “partial_ingredients” (either as a sibling collection or a subcollection), ensure that your trigger is only defined on the course documents:

   JAVASCRIPTCopied
   const { onDocumentCreated } = require("firebase-functions/v2/firestore");
   
   exports.createAggrIngr = onDocumentCreated("course/{courseID}", async (event) => {
     const v_courseid = event.params.courseID;
     console.log("v_courseid created: " + v_courseid);
     // Process the course document.
     return;
   });

3. Filter by Additional Checks (if needed):
   If somehow your course document is being updated by writes that include partial_ingredients data (or if you have a case where you cannot change the path), consider adding a guard in your code to ensure you process only documents that match your criteria. For example:

   JAVASCRIPTCopied
   exports.createAggrIngr = onDocumentCreated("course/{courseID}", async (event) => {
     // This event is for a creation event so event.data.before should be null.
     if (event.data.before) {
       // Not a true creation event.
       return;
     }
   
     const v_courseid = event.params.courseID;
     // Optionally check for required fields that should be present in a course document.
     if (!event.data.after.toJSON().courseName) {
       // Not a proper course document.
       return;
     }
   
     console.log("v_courseid created: " + v_courseid);
     // Process the course creation.
     return;
   });

Summary

The key is to ensure that your trigger’s document path uniquely targets the course documents. Verify that partial ingredient documents are not accidentally written to (or under) the “course” collection. If they must be in the same document hierarchy, then add extra validation inside your function to filter out events that don’t belong.

By double‑checking your document paths and adding any necessary guard conditions, you can ensure that your Cloud Firestore trigger only processes the intended course creation events.