Can Eventarc Match Multiple Firestore Collections in a Single Path Pattern?

Below is an explanation based on the documentation:

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Matching Two Collections in a Single Pattern

The path pattern syntax used by Eventarc is not a full regular expression system. In short, you cannot define a single capture group that matches an alternative list (like "users" or "clients") using syntax such as:

NONECopied
{col=[uc]*s}/{id}
{col=[clients,users]}/{id}
{col=clients,users}/{id}

Each capture group is limited to a single [NameSegment] that can include literal characters and, optionally, one wildcard. This means that you cannot express a disjunction (i.e. alternative matching of "users" or "clients") within a single capture group.

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Allowed Characters and Structure

The allowed characters listed (such as \w, \s, \t, ~@#$%&.,?:;+='[]()-) represent the literal characters that the pattern can contain rather than components of a full regex. The syntax only supports:

• Literal characters
• A single wildcard element in a name segment
• A very limited structure that does not allow for regex alternation (e.g., you can't combine characters and wildcards into a complex regular expression)

So, for example, if you need a pattern that triggers on document creation for both users/ and clients/ collections, the current syntax does not support that in one pattern.

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Recommended Approach

Since a single pattern cannot match both collections, you have two main options:

1. Create Two Separate Triggers:
   One trigger for the users/{id} path and another for the clients/{id} path using separate Eventarc triggers.

2. Modify the Design:
   Consider refactoring your document structure so that a single collection is used, or introduce a common path component that both collections share if that meets your application requirements. This common component can then be captured by a single path pattern.

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Conclusion

The path pattern syntax for triggering Cloud Functions v2 in Eventarc is intentionally simplified and does not support complex regex alternatives such as matching two separate collection names in one go. Therefore, to trigger the same Cloud Function for both users/ and clients/ on document creation, you will need to use separate trigger configurations or adjust your design accordingly.