How to sum a BIGINT column

[benthecarman]

I am trying to do a SUM on a BIGINT column but it doesn't seem possible. Is there any examples on how to do this? If I change my column to an i32 the normal examples work, not sure why it doesn't work for i64

[weiznich]

There is no fundamental difference between summing a INTEGER and a BIGINT column in diesel. You might want to check if you want to check if you specified the right return type on rust side. It needs to correspond to this type for sums of BigInt's (as it is specified by the sql standard).

Otherwise you need to provide a minimal example, including the complete error message you get from rustc if you need further help.

[benthecarman]

This is what I was doing

 let sum: Option<i64> = my_table::table
                .select(diesel::dsl::sum(my_table::big_int_col))
                .first(conn)?;

and I get this:

the trait bound `i64: FromSql<diesel::sql_types::Numeric, Pg>` is not satisfied                      
     --> src/models/routed_payment.rs:73:24                                                                            
      |                                                                                                                
 73   |                 .first(conn)?;                                                                                 
      |                  ----- ^^^^ the trait `FromSql<diesel::sql_types::Numeric, Pg>` is not implemented for `i64`, which is required by `SelectStatement<FromClause<my_table::table>

[weiznich]

Well as already written above: You need to use a rust side type that is compatible with the Numeric sql type. That's not the case for i64 so that's expected behavior. See the documentation for a list of compatible types.