Apache Pinot

Has anyone else encountered the `Expression cycle` problem when using an ingest transform function where the source field name matches the pinot column name? In my case I have geojson that has a geometry field containing coordinates (`{"geometry": {"coordinates": [-82.41959120338983, 35.61020539194915]}}` ). I'm looking for a way to convert those coordinates using `toSphericalGeography(stPoint(lon, lat))` into a column also named geometry.

<@UGRJA9TEH> Are you familiar with this `Expression cycle` issue? If so, would this require significant effort to fix?

what's the error ? or are you able to work around it with json, something like :
```"transformFunctions": {
  "rawGeometry": "jsonPathString(geometry, '$.coordinates')",
  "geometry": "toSphericalGeography(stPoint("
      + "jsonExtractScalar(rawGeometry, '$[0]', 'DOUBLE'), "
      + "jsonExtractScalar(rawGeometry, '$[1]', 'DOUBLE') ))"
}```

oh, I think that's impossible because you defined `geometry` in the pinot schema

How much effort would it take to make this possible?

it's tricky because your source column: `geometry` data type is different than the destination column: `geometry`  type

technically pinot will just read the column as the defined type and may throw exception before the transform happens

I would suggest to change to a new column in the pinot schema, in query, you can always make alias

I want to be able to change the data type without changing the name

then need to check how to use `TransformPipeline` to process those rows

<@UGRJA9TEH> The issue appears to be that `ExpressionTransformer.topologicalSort` treats all function arguments as pinot columns that require circular dependency checking. What are your thoughts on allowing self-referencing (argument name matches pinot column name) when the `functionEvaluator` contains JSON and other similar functions? For example, `geometry = toSphericalGeography(stPoint(JSONPATHDOUBLE(geometry, '$.coordinates[0]'), JSONPATHDOUBLE(geometry, '$.coordinates[1]')))`

I think we can add a config to override this column 

In which way could the column be overridden?