Question
A field called _id appears in the table that Webhooks are written to. This was not sent as part of the event payload. Where does it come from?
Environment
Connector: Webhooks
Answer
The _id field is generated by Google Pub/Sub which Fivetran uses to manage topic subscriptions.
Cause
This is an id that is guaranteed to be unique within a topic. In the context of Fivetran, a topic will often correlate to the Webhook endpoint in your Webhook connector. Google's definition of that ID is shared below. Please find the documentation here, under MessageId:
ID of this message, assigned by the server when the message is published. Guaranteed to be unique within the topic. This value may be read by a subscriber that receives aPubsubMessagevia aPullcall or a push delivery. It must not be populated by the publisher in aPublishcall.