SharePoint Connector is caching old Taxonomy Field labels

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Posted on by Ghanjys_

Hi,

I'm experiencing issues with caching of Taxonomy field values from a SharePoint list.

We have a SharePoint list that stores sales data linked to a cost center. This Cost center is a Taxonomy Field.

The list items are displayed in a Data table in Power Apps.

About a month ago we had to rename all cost centers in the Term Store manager in SharePoint.

This all went fine in SharePoint, The data was synced to the Hidden Taxonomy List, metadata and search results. No issues.

In Power Apps we are still seeing the old values for existing items, though in the New Form the new values are displayed.

What we see in the Data table:

When I look into the network traffic with developer tools, the following data is returned:

The SharePoint list correctly shows the new values for these items:

When I look up the item corresponding to WssId 980 in the Hidden Taxonomy List in SharePoint, this also has the correct value:

Does anybody know how to get the up-to-date data into Power Apps?

How does the caching behind the SharePoint Connector work? I couldn't find any documentation about this.

I have already refreshed the Datasource in Power Apps and removed and added the list again. Same results.

Loading the data in a new blank Power App has the same result.

(I thought the terms might have labels in other languages that I missed, but that's not the case.)

Any help would be greatly appreciated. Thanks!

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Ghanjys_ 11 on at

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So we managed to solve this issue by trial and error and have a pretty good idea about what happened here.

Using Chrome Developer Tools we saw that PowerApps calls a service in Azure, in our case https://europe-001.azure-apim.net/invoke, when it accesses the SharePoint data source. In it's headers it contains the query where the data set is stored (Azure Tables?), so it is not a live query on SharePoint but it uses a cache.

The table in this dataset is updated when a change is detected on the original SharePoint list. We assume the "GetChanges" method in the SharePoint API is used for this.

However, changes in the Term Store (like renaming terms) are synchronized from the Term Store to the different Lists and Libraries in SharePoint (and an intermediary "Hidden Taxonomy List") by a timer job 'Taxonomy Update Scheduler'.
We assume that this back-end service does not trigger the changes as a normal Update action would. Hence the changes are never copied tot the table that is being queried from Power Apps and the old values stay there forever.

We used a PnP Powershell script to trigger an update on every item in this list.
Get-PnPListItem -List "Offers" | % { Write-Host $_.FieldValues.Title Set-PnPListItem -List Offers -Identity $_.Id -Values @{OurCostCenterExtManaged=$_.FieldValues.OurCostCenterExtManaged.TermGuid} -SystemUpdate }

This is the minimal action that would trigger the update for us, so using SystemUpdate and by setting the field specifically (updating another field like Title for example did not work, so the trigger is field-based not row-based).

This is far from an ideal solution. If anyone has a better one, I'm all ears. 😉

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paherna on at

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Hi @Ghanjys_,

The behavior you were seeing is effectively by design. This occurs because the labels are not being fetched from the Taxonomy store but from the item itself, due to performance considerations.

The Label will be displayed as it was in the taxonomy store when it was written to the item (i.e. selecting from the dropdown and assigning the value to the item). Hence, when querying the data from Power Apps / Power Automate, it shows the pre-stored value. Any changes made to the Taxonomy Value in the Term Store will not be reflected until overridden on the SharePoint list item once more.

Hope this sheds some light as to why you were experiencing the above.

Thanks!

Community Support Team - Paola

If this Post helps, then please consider Accept as solution to help the other members find it more quickly.

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Ghanjys_ 11 on at

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Hi @paherna ,

Thanks for your feedback! Can you confirm that in this case it was some kind of intermediary storage / cache in Power Apps or the SharePoint connector that wasn't updated?

We made sure that all changes in the Term Store had fully propagated to the SharePoint list. We could see the new values in the UI, using CSOM / REST queries and Graph.
Only when going through Power Apps did we see the old values.

If the solution was designed like this, it comes with a major drawback since there is no way to refresh the data shown in Power Apps and the users would be working with old data without knowing it.

The only way to trigger the refresh is by performing an update in SharePoint item-by-item. For an end-user this not really a feasible solution for a large list.
He will have to edit each item, replace the old value with a dummy value and reset the original value. Apart from taking hours of time this could have side effects like triggering alerts, screwing up your data (Modified by fields are updated).

That being said, the probability of this occurring is pretty low an acceptable if it was documented. In the end I'm glad we found a workaround! 😉

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