Select into tuple

[billy1624]

New Features

• Added Select::into_tuple()

Breaking Changes

• Added TryGetable::try_get_by_index()
• Added TryGetableMany::try_get_many_by_index()

[tyt2y3]

I like the overall API 👍

However I think there is too much code duplication, and I think it is possible to refactor try_get_by_index and try_get with a common try_get_by<T>

[billy1624]

Hey @tyt2y3, I'm thinking something like this. What do you think?

pub enum TryGetColumn {
    Name(String),
    Index(usize),
}

pub trait IntoTryGetColumn {
    fn into_try_get_column() -> TryGetColumn;
}

impl IntoTryGetColumn for &str { ... }
impl IntoTryGetColumn for (&str, &str) { ... }
impl IntoTryGetColumn for String { ... }
impl IntoTryGetColumn for (String, String) { ... }
impl IntoTryGetColumn for usize { ... }

pub trait TryGetable: Sized {
    fn try_get<T>(res: &QueryResult, col: T) -> Result<Self, TryGetError>
    where
        T: IntoTryGetColumn;
}

impl sqlx::ColumnIndex<MySqlRow> for TryGetColumn { ... }
impl sqlx::ColumnIndex<SqliteRow> for TryGetColumn { ... }
impl sqlx::ColumnIndex<PgRow> for TryGetColumn { ... }

[tyt2y3]

I think the original sqlx try_get is generic over usize and str as index, so we probably don't need the TryGetColumn enum?

The SQLx type system looks like the following:

mod private_column_index {
    pub trait Sealed {}

    impl Sealed for usize {}
    impl Sealed for str {}
    impl<T> Sealed for &'_ T where T: Sealed + ?Sized {}
}

Wouldn't the following work?

fn try_get_by<I: Index>(res: &QueryResult, idx: I) -> Result<Self, TryGetError> {

[billy1624]

I think it won't work :(

fn try_get_by<I: Index>(res: &QueryResult, idx: I) -> Result<Self, TryGetError> { ... }

SQLx try_get takes &str / usize but here the compiler only knows the type implemented Index trait.

Also, I just found that we cannot implement sqlx::ColumnIndex in foreign crate because it's being sealed. https://docs.rs/sqlx/latest/sqlx/trait.ColumnIndex.html

// Not possible
impl sqlx::ColumnIndex<MySqlRow> for TryGetColumn { ... }
impl sqlx::ColumnIndex<SqliteRow> for TryGetColumn { ... }
impl sqlx::ColumnIndex<PgRow> for TryGetColumn { ... }

Then, we have no choice but to store String / usize and supply that to SQLx's try_get. So, I afraid this is the "only" way?

pub enum TryGetColumn {
    Name(String),
    Index(usize),
}

pub trait IntoTryGetColumn {
    fn into_try_get_column() -> TryGetColumn;
}

[tyt2y3]

Well, no and yes and no

[tyt2y3]

Self approve