Rust with sqlx::postgres and i64

Question

I'm new to Rust, and trying to implement an API using sqlx and PostgresQL. When reading about PostgresQL, it seems like it doesn't support u64, as MySQL does. So I have changed my code to i64, as documented here.

However it seems like some of my code still expects a u64 value:

An example of the code:

pub async fn drop_table(&self) -> Result<i64, sqlx::Error> {
    sqlx::query("DROP TABLE IF EXISTS users;")
        .execute(&*self.pool)
        .await
}

And the error it produces:

error[E0308]: mismatched types
 --> src\dao\user_dao.rs:7:9
  |
7 | /         sqlx::query("DROP TABLE IF EXISTS users;")
8 | |             .execute(&*self.pool)
9 | |             .await
  | |__________________^ expected `i64`, found `u64`
  |
  = note: expected enum `std::result::Result<i64, _>`
             found enum `std::result::Result<u64, _>`

I could probably cast the variable, but that could end up in a panic at runtime, so what would be the proper way to handle it?

I've used this as a reference application.

Answer 1

The reference application is using sqlx v0.3.5 and in that version of sqlx the execute method always returns a Result<u64, sqlx::Error> regardless of whether you're executing the query on a PostgresQL connection or a MySQL connection. The u64 represents the number of rows affected by executing the query and will always be unsigned. You should update the signature of drop_table to reflect that:

pub async fn drop_table(&self) -> Result<u64, sqlx::Error> {
    sqlx::query("DROP TABLE IF EXISTS users;")
        .execute(&*self.pool)
        .await
}