nit: transforms Coral IR function ..... to Spark compatible operator named_struct....

Not sure if it's suitable to call it Coral IR function, I think it's a function in CoralSqlNode converted from Coral IR?

in the path:
source SQL -> sourceSqlNode1 -> CoralSqlNode1 -> CoralRelNode -> CoralSqlNode2 -> TargetLangSqlNode -> target SQL

if an operator is present in CoralSqlNode1, CoralRelNode, CoralSqlNode2 and we transform this operator when we go to LanguageSqlNode, such operators can be called Coral IR functions.

as per the current status of our code base -
hive SQL -> HiveSqlNode (same as CoralSqlNode1) -> CoralRelNode -> CoralSqlNode2 -> SparkSqlNode -> Spark SQL
I think this operator qualifies as Coral Operator

Thanks for clarification, do you mean an operator is a Coral IR function if it appears in CoralSqlNode1 / CoralRelNode / CoralSqlNode2 or CoralSqlNode1 & CoralRelNode & CoralSqlNode2?
Not sure because it doesn't appear in CoralSqlNode1.

for a corresponding input hive SQL, what is the operator we use in the SqlNode representation? how do we represent the named_struct on LHS?

but generally yes, an operator present in CoralSqlNode1 would be present in CoralRelNode and then generated back in CoralSqlNode2.

It's still represented as named_struct in CoralSqlNode1, and Calcite converts it to CAST(ROW: RECORD_TYPE) in RelNode.

I see. In that case, could you investigate if it's possible to add a lightweight override in CoralRelNodeToCoralSqlNode to such that the coralSqlNode2 generated uses the same operator named_struct as coralSqlNode1?

Opened #357 for tracking.