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Add support for ordering with NULLS FIRST or NULLS LAST in postgres.

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This commit is contained in:
Rasmus Kaj 2016-08-07 00:43:17 +02:00
parent 8bebe479cb
commit 9d4054c62d
3 changed files with 99 additions and 0 deletions
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4
CHANGELOG.md
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@ -5,6 +5,10 @@ for Rust libraries in [RFC #1105](https://github.com/rust-lang/rfcs/blob/master/
## Unreleased
* Added support for PostgreSQL `NULLS FIRST` and `NULLS LAST` when sorting.
See http://docs.diesel.rs/diesel/prelude/trait.SortExpressionMethods.html
for details.
## [0.7.0] - 2016-08-01
### Added

92
diesel/src/pg/expression/expression_methods.rs
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@ -211,3 +211,95 @@ impl<T, ST> ArrayExpressionMethods<ST> for T where
T: Expression<SqlType=Array<ST>>,
{
}
use expression::predicates::{Asc, Desc};
pub trait SortExpressionMethods : Sized {
/// Specify that nulls should come before other values in this ordering.
/// Normally, nulls come last when sorting in ascending order and first
/// when sorting in descending order.
///
/// # Example
///
/// ```rust
/// # #[macro_use] extern crate diesel;
/// # include!("src/doctest_setup.rs");
/// #
/// # table! {
/// # users {
/// # id -> Integer,
/// # name -> VarChar,
/// # }
/// # }
/// #
/// # table! {
/// # foos {
/// # id -> Integer,
/// # foo -> Nullable<Integer>,
/// # }
/// # }
/// #
/// # fn main() {
/// # let connection = connection_no_data();
/// # connection.execute("DROP TABLE IF EXISTS foos").unwrap();
/// connection.execute("CREATE TABLE foos (id SERIAL PRIMARY KEY, foo INTEGER)").unwrap();
/// connection.execute("INSERT INTO foos (foo) VALUES (NULL), (1), (2)").unwrap();
///
/// # use self::foos::dsl::*;
/// assert_eq!(Ok(vec![Some(1), Some(2), None]),
/// foos.select(foo).order(foo.asc()).load(&connection));
/// assert_eq!(Ok(vec![None, Some(1), Some(2)]),
/// foos.select(foo).order(foo.asc().nulls_first()).load(&connection));
/// # connection.execute("DROP TABLE foos").unwrap();
/// # }
/// ```
fn nulls_first(self) -> NullsFirst<Self> {
NullsFirst::new(self)
}
/// Specify that nulls should come after other values in this ordering.
/// Normally, nulls come last when sorting in ascending order and first
/// when sorting in descending order.
///
/// # Example
///
/// ```rust
/// # #[macro_use] extern crate diesel;
/// # include!("src/doctest_setup.rs");
/// #
/// # table! {
/// # users {
/// # id -> Integer,
/// # name -> VarChar,
/// # }
/// # }
/// #
/// # table! {
/// # foos {
/// # id -> Integer,
/// # foo -> Nullable<Integer>,
/// # }
/// # }
/// #
/// # fn main() {
/// # let connection = connection_no_data();
/// # connection.execute("DROP TABLE IF EXISTS foos").unwrap();
/// connection.execute("CREATE TABLE foos (id SERIAL PRIMARY KEY, foo INTEGER)").unwrap();
/// connection.execute("INSERT INTO foos (foo) VALUES (NULL), (1), (2)").unwrap();
///
/// # use self::foos::dsl::*;
/// assert_eq!(Ok(vec![None, Some(2), Some(1)]),
/// foos.select(foo).order(foo.desc()).load(&connection));
/// assert_eq!(Ok(vec![Some(2), Some(1), None]),
/// foos.select(foo).order(foo.desc().nulls_last()).load(&connection));
/// # connection.execute("DROP TABLE foos").unwrap();
/// # }
/// ```
fn nulls_last(self) -> NullsLast<Self> {
NullsLast::new(self)
}
}
impl<T> SortExpressionMethods for Asc<T> {}
impl<T> SortExpressionMethods for Desc<T> {}

3
diesel/src/pg/expression/predicates.rs
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@ -1,6 +1,9 @@
use pg::Pg;
use query_builder::QueryBuilder;
infix_predicate!(IsNotDistinctFrom, " IS NOT DISTINCT FROM ", backend: Pg);
infix_predicate!(OverlapsWith, " && ", backend: Pg);
infix_predicate!(Contains, " @> ", backend: Pg);
infix_predicate!(IsContainedBy, " <@ ", backend: Pg);
postfix_expression!(NullsFirst, " NULLS FIRST", ());
postfix_expression!(NullsLast, " NULLS LAST", ());