Why can't we use multi-value column in funciton_column pair of Startree Index? I understand limitation of using multi-value column in split order but we should be able to use it aggregation. Eg ->

spaces

is multi value column.

{
  "dimensionsSplitOrder": [
    "pdate"
  ],
  "functionColumnPairs": [
    "DISTINCTCOUNTHLLMV__spaces"
  ]
}

https://github.com/apache/pinot/blob/master/pinot-segment-local/src/main/java/org/apache/pinot/segment/local/utils/TableConfigUtils.java#L1309 IMO, we can avoid this check for aggregation column.

you are right, we can allow aggregations on MV. can you create a github issue - contributions welcome.

github issue - https://github.com/apache/pinot/issues/16569