Adding array functions pushdown to pinot

[xiangfu0]

Support pushing down Array functions to Pinot.

• Array functions(array_sum, array_min, array_max, array_average) inside aggregation functions or group by clause to Pinot.
• Boolean functions in Predicate: contains

E.g. For Presto query: SELECT sum(array_max(col)) FROM myTable WHERE contains(col, 1) , the pushdown pinot query is: SELECT sum(arrayMax(col)) FROM myTable WHERE col = 1

Test plan:
Unit tests and tested with local setup for array functions(array_sum, array_min, array_max, array_average, contains) pushdown to Pinot:

== RELEASE NOTES ==

Pinot Changes
* Support pushing down array functions `array_sum`, `array_min`, `array_max`, `array_average`, and `contains` to Pinot connector.

[xiangfu0]

@agrawaldevesh @dharakk

[agrawaldevesh]

I am having second thoughts about ARRAY_AGGREGATION_ALLOWED_PUSHDOWN_MAP: I am wondering if we should ditch the map and just have a case statement to handle the 4 or 5 of those keys separately ?

They are all somewhat custom anyway ... sometimes we special case on things like array_min/array_max and sometimes we look up the map.

I was wondering if the code would be simpler by having a couple of helper methods with case expressions instead of a map, to account for the customness.

[xiangfu0]

I am having second thoughts about ARRAY_AGGREGATION_ALLOWED_PUSHDOWN_MAP: I am wondering if we should ditch the map and just have a case statement to handle the 4 or 5 of those keys separately ?

They are all somewhat custom anyway ... sometimes we special case on things like array_min/array_max and sometimes we look up the map.

I was wondering if the code would be simpler by having a couple of helper methods with case expressions instead of a map, to account for the customness.

I overall feel, it would be simpler to have both map and switch case so we can have some common code logics to handle the function name conventions.

This is the first PR of pushing down array functions and I only implemented 4 functions. There would be more array functions to be pushed down.
Ref: https://prestodb.io/docs/current/functions/array.html and apache/pinot#6083

[agrawaldevesh]

Okay. I am fine with leaving the map there.

[agrawaldevesh]

LGTM

Please make sure to update the PR description with a test plan that enumerates some examples of what all presto array expressions can now be pushed into Pinot.

[agrawaldevesh]

I was wondering how type checking happens for these new array functions ? How do we check that the arguments to array_sum and contains for example are indeed arrays ?

What happens if I invoke those functions on scalar columns ?

Should we add some negative tests ?