Dylan1312 opened a new issue #8970: Expressions within aggregations can no longer use virtual columns URL: https://github.com/apache/incubator-druid/issues/8970 ### Affected Version 0.15.0-incubating 0.15.1-incubating 0.16.0-incubating ### Description Prior to 0.15.0, an expression within an aggregation could use a virtual column. In later versions it seems that a virtual column used within an expression will always evaluate to 0. This was useful as it allowed expressions using _time to be evaluated once per segment (within a virtual column) rather than evaluating it every aggregation operation. I'm still trying to decipher why but it looks like when the virtual column selector is loaded, the returned value is a "ArrayExprEval" which has a hardcoded value of 0 for asLong. bit of a contrived example but to show what's changed `{ "dataSource" : "test", "intervals" : [ "2019-11-01/2019-11-02" ], "granularity" : "all", "aggregations" : [ { "type" : "longSum", "name" : "computed_value", "expression" : "1 + two" } ], "virtualColumns" : [ { "name" : "two", "expression" : "2", "type" : "expression" } ], "queryType" : "timeseries" }` returns `[ { "timestamp": "2019-11-01T00:00:00.000Z", "result": { "computed_value": 1574832721 } } ]` on 0.14.2 but ` [ { "timestamp": "2019-11-01T00:00:00.000Z", "result": { "computed_value": 0 } } ] ` on 0.16.0
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