Function on_constraint 

pub fn on_constraint(constraint_name: &str) -> OnConstraint<'_>

Available on crate feature postgres_backend only.

Used to specify the constraint name for an upsert statement in the form ON CONFLICT ON CONSTRAINT. Note that constraint_name must be the name of a unique constraint, not the name of an index.

Example

use diesel::upsert::*;

diesel::sql_query("ALTER TABLE users ADD CONSTRAINT users_name UNIQUE (name)")
    .execute(conn)
    .unwrap();
let user = User {
    id: 1,
    name: "Sean",
};
let same_name_different_id = User {
    id: 2,
    name: "Sean",
};
let same_id_different_name = User {
    id: 1,
    name: "Pascal",
};

assert_eq!(
    Ok(1),
    diesel::insert_into(users).values(&user).execute(conn)
);

let inserted_row_count = diesel::insert_into(users)
    .values(&same_name_different_id)
    .on_conflict(on_constraint("users_name"))
    .do_nothing()
    .execute(conn);
assert_eq!(Ok(0), inserted_row_count);

let pk_conflict_result = diesel::insert_into(users)
    .values(&same_id_different_name)
    .on_conflict(on_constraint("users_name"))
    .do_nothing()
    .execute(conn);
assert!(pk_conflict_result.is_err());