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TheFifthJoin's avatar
TheFifthJoin
Advocate I
11 months ago
Solved

Materialized Lake View - 'Invalid Date, Invalid Date'

Recently started seeing some very strange behaviour following updating my OPDG to the August release where if we add or remove a column from a materialized lake view, other columns become 'Invalid Da...
data engineering
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  • V-yubandi-msft's avatar
    V-yubandi-msft
    11 months ago

    Hi TheFifthJoin ,

    Thank you for providing the details. Even reverting to a previous version may not fully resolve it, since cached metadata can persist across sessions and environments. anilgavhane , suggestions are still relevant and worth trying.
    For the

    "Private link check failed"

    This is probably not directly related to the MLV issue, but may be impacted by the same OPDG update. This error often occurs if

    1. The Fabric workspace or capacity isn’t properly registered in the Private DNS zone

    2. The Private Link endpoint is misconfigured or not fully propagated

    3. You’re using On Premises Data Gateway, which doesn’t fully support Private Link

    If you’re in a secure VNet environment, you might consider using the VNet Data Gateway, as it’s designed for Private Link and can help avoid these errors.

    Alternatively, you can

    1. Disable redirection temporarily and test creating the MLV with a new name and explicit casting
    2. Check Private DNS zone records to ensure Fabric endpoints are properly registered
    3. If using OPDG with Private Link, try switching to VNet Data Gateway

    Helpful Reference:
    Solved: Seeking Advice: Private Link and VNet Data Gateway... - Microsoft Fabric Community

    Thanks for prompt response anilgavhane .

    Regards,
    Yugandhar.

  • TheFifthJoin's avatar
    TheFifthJoin
    10 months ago

    Hi V-yubandi-msft 

     

    To update - bit of a mixed bag of solutions.. The rollback of the OPDG seemed to fix the columns going into strange orders when we added/removed a column from the materialized lake view. I've not seen this as a known issue, but rolling back seemed to resolve and we'll wait for a new update release before trying to update the OPDG again.

     

    The 'Invalid Date, Invalid Date' seems to be being displayed when my date value in the raw data is NULL. If we load this via the sql endpoint in SSMS, the fields display as null values as expected.. a bit of an odd display, but I believe its just a display quirk, rather than an actual issue with the data. Hopefully this will get addressed in a future release also, but for now, ignoring it is doing no harm as the 'Invalid Date, Invalid Date' message doesnt pull into powerBI visualisation either.

     

    Finally the Private link issue was a much wider issue that affected all of south-west connections. Something to do with an error in an update MS pushed - they address, rolled back internally, and the error disappeared.

     

    Thanks for checking back!

anilgavhane's avatar
anilgavhane
Super User
11 months ago

TheFifthJoin

This issue with Materialized Lake Views (MLVs) showing 'Invalid Date, Invalid Date' after schema changes—especially when dropping or adding columns—is likely tied to a metadata caching or schema inference bug introduced in the August OPDG update. You're not alone; similar instability has been reported across Fabric components following recent updates.

What Might Be Happening

  • Schema inference glitch: When you drop or add a column, Fabric may incorrectly re-infer data types for existing columns, especially if the metadata cache isn’t fully cleared.
  • Ghost metadata: Even after dropping and recreating the MLV, cached schema definitions may persist, causing type mismatches (e.g., treating a string column as a date).
  • Propagation delay: The delay you mentioned between drop and recreate might not be enough to flush internal metadata references.

    Suggested Workarounds

     

    • Explicit Casting in SQL
      Force the correct data type in your MLV SQL:

       

      SELECT CAST(title AS STRING) AS title, ...

       

       

       

      • Use a New MLV Name Temporarily
        Create the MLV under a different name to bypass cached metadata:

         

         

         

        CREATE MATERIALIZED LAKE VIEW IF NOT EXISTS `silver-ws`.silver_lh.core.people_v2 AS ...

         

         

        1. Clear Metadata via Workspace Restart
          If possible, restart the workspace or session to flush cached schema definitions.
        2. Raise a Ticket with Microsoft Support
          This behavior may be tied to the August OPDG release. Others have resolved similar issues by downgrading or applying a patch.

  • TheFifthJoin's avatar
    TheFifthJoin
    Advocate I
    11 months ago

    We rolled back the OPDG to June's release (our last known good configuration) and that doesnt seem to have resolved the issue at all. 

     

    As of this morning we're now also getting an error when trying to connect a session in a notebook

    "reason": "{\"reason\":\"Private link check failed.\",\"state\":\"private-link-check-failed\"}",

     

    Are these likely to be related?