topic Re: Copy Data activity - ErrorCode=FailedToUpsertDataIntoDeltaTable in Pipelines

Copy Data activity - ErrorCode=FailedToUpsertDataIntoDeltaTable

KerenLopez — Wed, 04 Feb 2026 15:24:53 GMT

Hi everyone!

I have a pipeline with a Copy Data activity that is loading data into a Delta table in a Lakehouse. The first ingestion runs successfully, but when I run the pipeline for a second time, the copy activity fails during the upsert operation with the following error:

ErrorCode=FailedToUpsertDataIntoDeltaTable,'Type=Microsoft.DataTransfer.Common.Shared.HybridDeliveryException,Message=Hit an error when upsert data to table in Lakehouse. Error message: Could not load file or assembly 'Microsoft.Bcl.HashCode, Version=1.0.0.0, Culture=neutral, PublicKeyToken=xxxxx' or one of its dependencies. El sistema no puede encontrar el archivo especificado.,Source=Microsoft.DataTransfer.Connectors.LakehouseTableConnector,''Type=System.IO.FileNotFoundException,Message=Could not load file or assembly 'Microsoft.Bcl.HashCode, Version=1.0.0.0, Culture=neutral, PublicKeyToken=xxxxx' or one of its dependencies. El sistema no puede encontrar el archivo especificado.,Source=TypeExtension,'

Has anyone encountered the same issue or have any ideas on what might be causing this? Any insights or troubleshooting steps would be greatly appreciated.

Thanks in advance!

Re: Copy Data activity - ErrorCode=FailedToUpsertDataIntoDeltaTable

v-dineshya — Thu, 05 Feb 2026 12:34:36 GMT

Hi KerenLopez ,

Thank you for reaching out to the Microsoft Community Forum.

Please try below things to fix the issue.

1. Turn on “Enable staging” for the Copy activity:

Open your pipeline --> Copy data activity --> Settings tab. Turn on Enable staging. Re-run the pipeline.

2. Use a staging table and MERGE in a Notebook:

Change sink to Files --> Parquet or a staging Delta table. Add a Notebook activity after the copy with a simple Delta MERGE INTO from staging to the target table.

Please check below settings.

1. Make sure the sink is a Lakehouse Table (Delta) rather than the SQL endpoint of the Lakehouse. The SQL endpoint in Fabric is read-only and can’t be used as a Copy sink for upsert.

2. Verify the key columns under Table action --> Upsert are correctly mapped and present in the incoming dataset. they will cause other upsert failures.

3. Avoid temporary tables in source-side stored procedures when possible, historical issues show these can behave differently across connectors and modes. If you need, test with a simplified SELECT to isolate whether the failure is due to source-side temp objects or the sink upsert path.

Please refer below links.

Solved: Copy activity fails to save data as delta table bu... - Microsoft Fabric Community

Solved: Failed to Upsert Data into Lakehouse Delta Table –... - Microsoft Fabric Community

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

Regards,

Dinesh

Re: Copy Data activity - ErrorCode=FailedToUpsertDataIntoDeltaTable

v-dineshya — Mon, 09 Feb 2026 04:40:48 GMT

Hi KerenLopez ,

We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. And, if you have any further query do let us know.

Regards,

Dinesh

Re: Copy Data activity - ErrorCode=FailedToUpsertDataIntoDeltaTable

KerenLopez — Tue, 10 Feb 2026 22:10:54 GMT

Hi v-dineshya,

Apologies for the delayed response 😅.

I wanted to let you know that the first option you suggested — “Enable staging” in the Copy activity — worked perfectly and resolved the issue.

Thank you very much for your support and for the clear explanation. I really appreciate your help.

Regards,
Keren.