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Implement array_ndims function #4178

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Aug 30, 2024
Merged

Implement array_ndims function #4178

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f2d4e25
Implement array_ndims function
danila-b Aug 17, 2024
614df9b
Fix the doc tests
weiznich Aug 30, 2024
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29 changes: 29 additions & 0 deletions diesel/src/pg/expression/functions.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1361,3 +1361,32 @@ define_sql_function! {
elem: E,
) -> Nullable<Array<Integer>>;
}

#[cfg(feature = "postgres_backend")]
define_sql_function! {
/// Returns the number of dimensions of the array
///
/// # Example
///
/// ```rust
/// # include!("../../doctest_setup.rs");
/// #
/// # fn main() {
/// # run_test().unwrap();
/// # }
/// #
/// # fn run_test() -> QueryResult<()> {
/// # use diesel::dsl::array_ndims;
/// # use diesel::sql_types::{Nullable, Array, Integer};
/// # let connection = &mut establish_connection();
///
/// // diesel currently only supports 1D arrays
/// let dims = diesel::select(array_ndims::<Array<Integer>, _>(vec![1, 2]))
/// .get_result::<i32>(connection)?;
/// assert_eq!(1, dims);
///
/// # Ok(())
/// # }
/// ```
fn array_ndims<Arr: ArrayOrNullableArray + SingleValue>(arr: Arr) -> Integer;
}
5 changes: 5 additions & 0 deletions diesel/src/pg/expression/helper_types.rs
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Expand Up @@ -451,3 +451,8 @@ pub type array_position_with_subscript<A, E, S> =
#[cfg(feature = "postgres_backend")]
pub type array_positions<A, E> =
super::functions::array_positions<SqlTypeOf<A>, SqlTypeOf<E>, A, E>;

/// Return type of [`array_ndims(array)`](super::functions::array_ndims())
#[allow(non_camel_case_types)]
#[cfg(feature = "postgres_backend")]
pub type array_ndims<A> = super::functions::array_ndims<SqlTypeOf<A>, A>;
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Is this even required for functions that do not have a generic return type and always return Integer?
I tried to remove it but without this generic arguments in auto_types explodes.

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It's required for the generic arguments. define_sql_function! generates a function signature as follows:

fn array_ndims<A, Arr>(arr: Arr) -> Integer
where Arr: AsExpression<A>, A: ArrayOrNullableArray + SingleValue>;

The AsExpression part allows us to automatically convert rust values (i.e. vec![1,2,3]) to sql side binds and at the same time it allows us to accept sql side expressions with the same type at the same location (i.e table::array_column). On the other hand the #[auto_type] macro expects exactly as many generic arguments as there are function parameters. The type def in then used to map that.

1 change: 1 addition & 0 deletions diesel_derives/tests/auto_type.rs
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Expand Up @@ -430,6 +430,7 @@ fn postgres_functions() -> _ {
array_position(pg_extras::array, pg_extras::id),
array_position_with_subscript(pg_extras::array, pg_extras::id, pg_extras::id),
array_positions(pg_extras::array, pg_extras::id),
array_ndims(pg_extras::array),
)
}

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