Comos Mirror - Missing _etag

[EricCarlson]

I created a Cosmos Mirror in my Fabric workspace which works great.

However the "_etag" column is missing.  I do see some other system columns like "_ts" and "_rid".  So why is _etag missing?  This column would be really useful for merging data changes to destination tables.

[v-nmadadi-msft]

Hi @EricCarlson  ,
Thanks for reaching out to the Microsoft fabric community forum.

First, refresh the Schemas and dbo node to determine if the tables are ready. Tables are automatically loaded after they're ready. If more columns aren't ready after a significant amount of time, use the Monitor replication pane to determine if any replication errors occurred.
Troubleshoot Microsoft Fabric mirrored databases from Azure Cosmos DB (Preview) - Microsoft Fabric |...

I hope this information helps. Please do let us know if you have any further queries.
Thank you

[Anonymous · Accepted solution]

Hi @EricCarlson ,

The _etag column is intentionally not exposed in Microsoft Fabric Cosmos DB mirrors. While system columns like _ts and _rid are included, _etag is excluded because it is an internal concurrency control token in Cosmos DB, not designed for analytical or replication scenarios. Fabric mirroring focuses on queryable data and metadata relevant for analytics, so _etag is omitted by design.

Use _ts for incremental merge logic in Fabric destination tables. Consider Cosmos DB Change Feed if you need guaranteed ordered updates. Treat _etag as an internal-only property it won’t be exposed in Fabric mirrors.

Please refer below links.

https://learn.microsoft.com/en-us/fabric/mirroring/azure-cosmos-db-troubleshooting

https://learn.microsoft.com/en-us/fabric/mirroring/troubleshooting.

If my response as resolved your issue please mark it as solution and give kudos.

Thanks,

Dinesh