Issue with Mirroring from Cosmos DB: Decimal Values Replicated as NULL in Fabric Mirroring

Hi everyone,

I’m running into an issue with Cosmos DB Mirroring in Microsoft Fabric, and I’d like to confirm whether others have experienced something similar, or if there are any alternative solutions or workarounds.

🧩 Scenario:

• I have a Cosmos DB container (with Synapse Link / Analytical Store enabled) that is being mirrored into a Fabric warehouse using the built-in Mirroring feature.

• The field "Total" is present in every document, and its values can be either integers (e.g., 6000) or floating-point numbers (e.g., 17.9, 15.1, 6000.0).

• Mirroring appears to work fine in general. However, I've discovered that when querying the mirrored table via the SQL Endpoint, any "Total" value that was originally a decimal (like 17.9) shows up as NULL.

• In contrast, values like 6000 or 6000.0 replicate correctly.

  ⚠️ Observed Behavior:

  • Example in Cosmos DB:

    { "id": "...", "Total": 17.9 }

    → In Fabric SQL Endpoint: Total = NULL

    ✅ What I’ve confirmed:

    • The "Total" field is always present and defined in the source documents.

    • This is not a case of missing data, but rather seems to be tied to how the schema is inferred or fixed during replication.

    • Microsoft documentation states that Analytical Store uses the first defined value to infer the schema, and that conflicting types (e.g., integer vs. float) may result in values being skipped or returned as NULL.

      ❓ What I'm looking for:

      • Has anyone else experienced this issue?

      • Are there best practices for handling numeric fields in Cosmos DB (especially when they can be int or float)?

      • Any known workarounds besides:

        • Forcing all values to be floats (e.g., 6000.0 instead of 6000)

        • Recreating the container with consistent types

        • Refreshing or recreating the mirroring after schema normalization

Thanks in advance for any suggestions or confirmations from the community!