`GroupingSet` Expr --> String Support about arrow-datafusion HOT 5 CLOSED

Hi @alamb, I am wondering whether is there a way to implement the cube and 'rollup' functions easily. the inner vector is expanded in the planner.

from arrow-datafusion.

Hi @xinlifoobar - another thing that we could potentially do is to work at this from the SQL statement level (rather than the Expr level)

As in implement a round trip test like this for a query with a grouping set:

https://github.com/apache/datafusion/blob/main/datafusion/sql/tests/sql_integration.rs#L4678-L4708

from arrow-datafusion.

I think from the Vec<Expr> could not mapping back to the only unique Vec<Vec<Expr>> and hence unparse the cube statement would be difficult. How about store another copy of origin Vec in the Cube and Rollup instance? i.e.,

pub enum GroupingSet {
    /// Rollup grouping sets
    Rollup(Vec<Expr>, Vec<Vec<Expr>>),
    /// Cube grouping sets
    Cube(Vec<Expr>, Vec<Vec<Expr>>),
    /// User-defined grouping sets
    GroupingSets(Vec<Vec<Expr>>),
}

from arrow-datafusion.

I made a mistake about the previous statements. The vector of cube and rollout is not expanded so the implement could be easy.

https://github.com/apache/datafusion/blob/main/datafusion/sql/src/expr/grouping_set.rs#L42-L81

from arrow-datafusion.

Thanks again @xinlifoobar

from arrow-datafusion.