topic Re: Mongo db mirroring in fabric throwing 'Running with Warnings' in Mirroring

Mongo db mirroring in fabric throwing 'Running with Warnings'

rsheltondavid — Thu, 11 Sep 2025 17:10:31 GMT

Hello Team,

We tried to mirror the mongo db into fabric and the set up is done but we've some tables that says 'Running with Warnings' and it is because of the datatypes in the same column.

ErrorCode: SchemaMergeFailure, Message: Failed to write table 'dbo\opportunity' due to schema mismatch. Schema merge failure due to potential invalid input. Cause: Type mismatch for column 'last_access'. Incoming type: 'string' (Nullable: True), existing type: 'double' (Nullable: True). ArtifactId: a38c79cb-7743-4e31-ad22-baebeda554a9

Knowing that mongo has now become compatible for mirroring, Is there a way to fix this issue?

We follow this github link for setup: GitHub - mongodb-partners/MongoDB_Fabric_Mirroring: Code to enable mirroring in Microsoft Fabric for MongoDB

Re: Mongo db mirroring in fabric throwing 'Running with Warnings'

v-saisrao-msft — Mon, 22 Sep 2025 03:48:53 GMT

Hi rsheltondavid,

Kindly check if there is a schema mismatch for the last_access column in your MongoDB collection. Check whether the values are stored as strings, doubles, or a combination of both. It’s best to store all values as strings to support both numeric and date formats. After the necessary changes for consistency, please restart the database mirroring process.

Thank you.

Re: Mongo db mirroring in fabric throwing 'Running with Warnings'

v-saisrao-msft — Mon, 15 Sep 2025 04:27:30 GMT

Hi rsheltondavid,

Have you had a chance to review the solution we shared earlier? If the issue persists, feel free to reply so we can help further.

Thank you.

Re: Mongo db mirroring in fabric throwing 'Running with Warnings'

v-saisrao-msft — Thu, 18 Sep 2025 04:53:01 GMT

Hi rsheltondavid,

We haven’t heard back from you in a while regarding your issue. let us know if your issue has been resolved or if you still require support.

Thank you.

Re: Mongo db mirroring in fabric throwing 'Running with Warnings'

v-saisrao-msft — Mon, 22 Sep 2025 03:50:13 GMT

Hi rsheltondavid,

Checking in to see if your issue has been resolved. let us know if you still need any assistance.

Thank you.

Re: Mongo db mirroring in fabric throwing 'Running with Warnings'

rsheltondavid — Wed, 24 Sep 2025 20:20:24 GMT

Hey,

Thanks for getting back to us. We've a mix of both on our mongo db end but the source is so large that we cannot change the source as yet. We've several columns with a combination data type in different collections. The data is landing fine as parquet files. The issues is only with the sync to the table. What would you suggest in such a scenario?

Re: Mongo db mirroring in fabric throwing 'Running with Warnings'

v-saisrao-msft — Thu, 25 Sep 2025 09:12:33 GMT

Hi rsheltondavid,

The error appears to be caused by a data type mismatch. Please verify that the column’s data type is consistent. After correcting it, try rerunning the database mirroring to see if the issue is resolved.

Thank you.

Re: Mongo db mirroring in fabric throwing 'Running with Warnings'

rsheltondavid — Thu, 25 Sep 2025 18:08:05 GMT

Hey v-saisrao-msft

Is fixing the source the only option or can we edit the source code before the mirroring to store the column as strings? We used this to set up the mirroring: GitHub - mongodb-partners/MongoDB_Fabric_Mirroring: Code to enable mirroring in Microsoft Fabric for...

Re: Mongo db mirroring in fabric throwing 'Running with Warnings'

v-saisrao-msft — Mon, 29 Sep 2025 11:35:39 GMT

Hi rsheltondavid,

Please update the source MongoDB so that the last_access field always maintains a consistent type.

In the MongoDB_Fabric_Mirroring repository, find the extraction or mapping code, such as mongodb_generic_mirroring.py or schema_utils.py.

Add a type cast for the last_access column before writing to Fabric:
if field_name == "last_access":
row[field_name] = str(row.get(field_name)) if row.get(field_name) is not None else None
Also, update the schema inference for this column to use string.

Thank you.

Re: Mongo db mirroring in fabric throwing 'Running with Warnings'

v-saisrao-msft — Mon, 06 Oct 2025 04:12:01 GMT

Hi rsheltondavid,

Have you had a chance to review the solution we shared earlier? If the issue persists, feel free to reply so we can help further.

Thank you.