The filter config needs a function that evaluates to boolean https://docs.pinot.apache.org/developers/advanced/ingestion-level-transformations#filtering
So far, we were able to use Groovy for expressing such fucntions. Starting release 0.10.0, Groovy is disabled by default, and also due to security concerns might not be the best choice to use even if explicitly enabled.
This leaves us with only being able to use regular Scalar Functions in filterFunction. However, we don't have sufficient scalar functions which evaluate to boolean (only ones I could find are startsWith and endsWith in StringFunctions.

Goal: Add all commonly used comparison functions (like equals, no equals, greater than, less than etc). We should be able to express such functions completely without Groovy "filterFunction": "Groovy({timestamp < 1589007600000}, timestamp)", "filterFunction": "Groovy({(campaign == \"X\" || campaign == \"Y\") && prices.sum() < 100}, prices, campaign)"