Posted September 7, 20222 yr Detailed description This is a Breaking change when using window functions inside partition operator sub-query scope. Window functions require a serialized/ordered input. There is a bug in Azure Data Explorer logic that allows using window functions inside the partition operator when the ordering is performed outside the partition query scope like this: T | where Timestamp > ago(1d) | order by Timestamp asc | partition by key ( extend next_value = next(value) ... ) This kind of query currently works unintentionally and sometimes the output is not correct. We’re planning to make a change that will fail this kind of queries by throwing a semantic error indicating that the input to the window function is not serialized. Required change Fix all relevant queries by pushing the ordering inside the partition subquery like shown below. T | where Timestamp > ago(1d) | partition by key ( order by Timestamp asc | extend next_value = next(value) ... ) Schedule & plan Support for previous window function pattern will be blocked - ETA: November 30, 2022 Continue reading...
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