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use backend::Backend;
use dsl::{Filter, IntoBoxed};
use expression::{AppearsOnTable, SelectableExpression};
use query_builder::returning_clause::*;
use query_builder::where_clause::*;
use query_builder::*;
use query_dsl::methods::{BoxedDsl, FilterDsl};
use query_dsl::RunQueryDsl;
use query_source::Table;
use result::QueryResult;
#[derive(Debug, Clone, Copy, QueryId)]
#[must_use = "Queries are only executed when calling `load`, `get_result` or similar."]
/// Represents a SQL `DELETE` statement.
///
/// The type parameters on this struct represent:
///
/// - `T`: The table we are deleting from.
/// - `U`: The `WHERE` clause of this query. The exact types used to represent
/// this are private, and you should not make any assumptions about them.
/// - `Ret`: The `RETURNING` clause of this query. The exact types used to
/// represent this are private. You can safely rely on the default type
/// representing the lack of a `RETURNING` clause.
pub struct DeleteStatement<T, U, Ret = NoReturningClause> {
table: T,
where_clause: U,
returning: Ret,
}
/// A `DELETE` statement with a boxed `WHERE` clause
pub type BoxedDeleteStatement<'a, DB, T, Ret = NoReturningClause> =
DeleteStatement<T, BoxedWhereClause<'a, DB>, Ret>;
impl<T, U> DeleteStatement<T, U, NoReturningClause> {
pub(crate) fn new(table: T, where_clause: U) -> Self {
DeleteStatement {
table: table,
where_clause: where_clause,
returning: NoReturningClause,
}
}
/// Adds the given predicate to the `WHERE` clause of the statement being
/// constructed.
///
/// If there is already a `WHERE` clause, the predicate will be appended
/// with `AND`. There is no difference in behavior between
/// `delete(table.filter(x))` and `delete(table).filter(x)`.
///
/// # Example
///
/// ```rust
/// # #[macro_use] extern crate diesel;
/// # include!("../../doctest_setup.rs");
/// #
/// # fn main() {
/// # use schema::users::dsl::*;
/// # let connection = establish_connection();
/// let deleted_rows = diesel::delete(users)
/// .filter(name.eq("Sean"))
/// .execute(&connection);
/// assert_eq!(Ok(1), deleted_rows);
///
/// let expected_names = vec!["Tess".to_string()];
/// let names = users.select(name).load(&connection);
///
/// assert_eq!(Ok(expected_names), names);
/// # }
/// ```
pub fn filter<Predicate>(self, predicate: Predicate) -> Filter<Self, Predicate>
where
Self: FilterDsl<Predicate>,
{
FilterDsl::filter(self, predicate)
}
/// Boxes the `WHERE` clause of this delete statement.
///
/// This is useful for cases where you want to conditionally modify a query,
/// but need the type to remain the same. The backend must be specified as
/// part of this. It is not possible to box a query and have it be useable
/// on multiple backends.
///
/// A boxed query will incur a minor performance penalty, as the query builder
/// can no longer be inlined by the compiler. For most applications this cost
/// will be minimal.
///
/// ### Example
///
/// ```rust
/// # #[macro_use] extern crate diesel;
/// # include!("../../doctest_setup.rs");
/// #
/// # fn main() {
/// # run_test().unwrap();
/// # }
/// #
/// # fn run_test() -> QueryResult<()> {
/// # use std::collections::HashMap;
/// # use schema::users::dsl::*;
/// # let connection = establish_connection();
/// # let mut params = HashMap::new();
/// # params.insert("sean_has_been_a_jerk", true);
/// let mut query = diesel::delete(users)
/// .into_boxed();
///
/// if params["sean_has_been_a_jerk"] {
/// query = query.filter(name.eq("Sean"));
/// }
///
/// let deleted_rows = query.execute(&connection)?;
/// assert_eq!(1, deleted_rows);
///
/// let expected_names = vec!["Tess"];
/// let names = users.select(name).load::<String>(&connection)?;
///
/// assert_eq!(expected_names, names);
/// # Ok(())
/// # }
/// ```
pub fn into_boxed<'a, DB>(self) -> IntoBoxed<'a, Self, DB>
where
DB: Backend,
Self: BoxedDsl<'a, DB>,
{
BoxedDsl::internal_into_boxed(self)
}
}
impl<T, U, Ret, Predicate> FilterDsl<Predicate> for DeleteStatement<T, U, Ret>
where
U: WhereAnd<Predicate>,
Predicate: AppearsOnTable<T>,
{
type Output = DeleteStatement<T, U::Output, Ret>;
fn filter(self, predicate: Predicate) -> Self::Output {
DeleteStatement {
table: self.table,
where_clause: self.where_clause.and(predicate),
returning: self.returning,
}
}
}
impl<'a, T, U, Ret, DB> BoxedDsl<'a, DB> for DeleteStatement<T, U, Ret>
where
U: Into<BoxedWhereClause<'a, DB>>,
{
type Output = BoxedDeleteStatement<'a, DB, T, Ret>;
fn internal_into_boxed(self) -> Self::Output {
DeleteStatement {
table: self.table,
where_clause: self.where_clause.into(),
returning: self.returning,
}
}
}
impl<T, U, Ret, DB> QueryFragment<DB> for DeleteStatement<T, U, Ret>
where
DB: Backend,
T: Table,
T::FromClause: QueryFragment<DB>,
U: QueryFragment<DB>,
Ret: QueryFragment<DB>,
{
fn walk_ast(&self, mut out: AstPass<DB>) -> QueryResult<()> {
out.push_sql("DELETE FROM ");
self.table.from_clause().walk_ast(out.reborrow())?;
self.where_clause.walk_ast(out.reborrow())?;
self.returning.walk_ast(out.reborrow())?;
Ok(())
}
}
impl<T, U> AsQuery for DeleteStatement<T, U, NoReturningClause>
where
T: Table,
T::AllColumns: SelectableExpression<T>,
DeleteStatement<T, U, ReturningClause<T::AllColumns>>: Query,
{
type SqlType = <Self::Query as Query>::SqlType;
type Query = DeleteStatement<T, U, ReturningClause<T::AllColumns>>;
fn as_query(self) -> Self::Query {
self.returning(T::all_columns())
}
}
impl<T, U, Ret> Query for DeleteStatement<T, U, ReturningClause<Ret>>
where
T: Table,
Ret: SelectableExpression<T>,
{
type SqlType = Ret::SqlType;
}
impl<T, U, Ret, Conn> RunQueryDsl<Conn> for DeleteStatement<T, U, Ret> {}
impl<T, U> DeleteStatement<T, U, NoReturningClause> {
/// Specify what expression is returned after execution of the `delete`.
///
/// # Examples
///
/// ### Deleting a record:
///
/// ```rust
/// # #[macro_use] extern crate diesel;
/// # include!("../../doctest_setup.rs");
/// #
/// # #[cfg(feature = "postgres")]
/// # fn main() {
/// # use schema::users::dsl::*;
/// # let connection = establish_connection();
/// let deleted_name = diesel::delete(users.filter(name.eq("Sean")))
/// .returning(name)
/// .get_result(&connection);
/// assert_eq!(Ok("Sean".to_string()), deleted_name);
/// # }
/// # #[cfg(not(feature = "postgres"))]
/// # fn main() {}
/// ```
pub fn returning<E>(self, returns: E) -> DeleteStatement<T, U, ReturningClause<E>>
where
E: SelectableExpression<T>,
DeleteStatement<T, U, ReturningClause<E>>: Query,
{
DeleteStatement {
table: self.table,
where_clause: self.where_clause,
returning: ReturningClause(returns),
}
}
}