Custom connector: refresh in Desktop without clearing cache gives 'The key didn't match any rows'

[bl_g]

We have created a Power BI custom connector that connects to our webservice. The connector works with a nested folder structure. The user selects one or more tables from one or more folders. Part of the connector's structure (folder and table names) is fixed, while other parts are dynamic (depend on the data the user has in their webservice).

The problem which our users experience, is that they often have to clear the cache in Power BI Desktop for a refresh to work successfully. If they don't clear the cache, they get an error saying: 'The key didn't match any rows in the table'. To our best knowledge, this error means that Power BI cannot find the table with the given name and folder-path.

However, this error also occurs if a user refreshes a (report created with a) table that has a fixed name and path, in which case this error seems to not apply.

Is this a known issue? Is there a fix or workaround (other than clearing the cache each time before a refresh)? Is it indeed caused by the custom connector's structure being partly dynamic?

Any help is greatly appreciated!

[Akash_Varuna]

Hi @bl_g It might be because of the difference between cached metadata and the dynamic structure of your custom connector. To fix this, disable metadata caching using [IsResourcePathRequired = false], and implement schema refresh logic in your connector. Minimize overly dynamic structures where possible and guide users to clear cache only as a last resort. Debug with Data Source Diagnostics to pinpoint schema mismatches.

[freginier]

Hi

Yes, this is a known issue when using custom connectors with dynamic metadata in Power BI. The error 'The key didn't match any rows in the table' typically appears when Power BI's data preview or schema cache is out of sync with the actual structure returned by the connector.

Cause:

Power BI caches metadata (e.g., schema, table names, paths) during navigation. If your connector has dynamic folder or table structures that change between loads, Power BI may try to reference outdated paths or fields, resulting in the key mismatch error.

Workarounds:

1. Implement SupportsDirectQuery = false in the connector
   Forces Power BI to re-fetch metadata during refresh rather than rely on cache.

2. Use Odbc.DataSource-style navigation table
   Implement the NavigationTable pattern using fixed columns like Name, Kind, Item, Data. This helps Power BI recognize stable navigation paths and reduces cache mismatch risk.

3. Add static fallback metadata
   For dynamic tables, return a consistent schema or wrapper that hides volatility from Power BI (e.g., include all possible columns and use nulls where not applicable).

4. Force cache busting programmatically
   Use a query parameter (e.g., version or timestamp) in the URL or function signature so each refresh appears new to Power BI.

5. Document and guide users to "File > Options > Data Load > Clear cache" when errors occur — though not ideal, it's the only workaround when metadata volatility is unavoidable.

There’s no full fix currently unless the dynamic structure is stabilized or wrapped.

freginier