Trouble with postgres query in entity framework core

Question

So I have a table as such:

[Table("Box", Schema = "dbo")]
    public partial class Box
    {
        [Column("eventId")]
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        [StringLength(200)]
        public int EventId {get;set;}

        [Column("uuid")]
        public int Uuid {get;set;}

        [Column("localIndex")]
        public int LocalIndex {get;set;}

        [Column("rack")]
        public string Rack {get;set;}

        [Column("shelf")]
        public string Shelf{get;set;}

        [Column("fag")]
        public string Fag{get;set;}

        [Column("municipality")]
        public string Municipality {get;set;}

        [Column("organization")]
        public string Organization {get;set;}

        [Column("Entries")]
        public string Entries{get;set;}

    }

The database is event driven so the uuid for a particular box will remain constant however everything else may change, so what I want to get is the newest edition of all unique UUID boxes. Is there some succinct query I can run to accomplish this?

As right now as a temporary solution I just get all the boxes which match a specific where clause and run the result through this function:

let getLatest (list : Box list) = 
    list 
    |> List.filter(fun x -> list 
                            |> List.forall(fun y ->         
                                    not (y.uuid = x.uuid && y.eventId > x.eventId)))

Which needless to say is probably not the best way of doing it but it functions. However if anyone has any idea it would be most appreciated.

Answer 1

I would solve this problem by grouping your boxes by UUID , then ordering each group by eventId and taking first record from each group. In code it would look like:

let getLatest2 (list : Box list) = 
    list 
    |> List.groupBy (fun x-> x.uuid)
    |> List.map (fun (uuid, values) -> 
                    values 
                    |> List.sortByDescending (fun x->x.eventId) 
                    |> List.head)

To be honest, I'm not sure if it will be correctly translated with EF to SQL query or if it has any advantage over your original solution.