AzureDiagnstics table is used by many Azure Services when you send diagnostic logs thus the 500 column limit that Microsoft is trying to fix for that table. When you hit that limit there is currently the described workaround but let’s say you have used one service that was sending logs and you no longer use that service. The logs associated with that service are yet to purged but you also want to clean up any custom columns that the service was using. That way you can free some slots for new custom columns for new services that will send logs to AzureDiagnostics table. Of course you can delete the custom column from Log Analytics blade but you do not want to delete a custom column that is also used by another service. This will be a short blog post that I will show you how to find if custom column is used by more than one service by using Kusto query language.
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