diesel/query_builder/update_statement/

mod.rs

pub(crate) mod batch_update;
pub(crate) mod changeset;
pub(super) mod target;

use private::AllowFilterForUpdate;

use crate::QuerySource;
use crate::backend::DieselReserveSpecialization;
use crate::dsl::{Filter, IntoBoxed};
use crate::expression::{
    AppearsOnTable, Expression, MixedAggregates, SelectableExpression, ValidGrouping, is_aggregate,
};
use crate::query_builder::returning::{
    NoReturningClause, ReturningClause, ReturningQuerySource, UpdateStmt,
};
use crate::query_builder::where_clause::*;
use crate::query_builder::*;
use crate::query_dsl::RunQueryDslSupport;
use crate::query_dsl::methods::{BoxedDsl, FilterDsl};
use crate::query_source::Table;
use crate::result::EmptyChangeset;
use crate::result::Error::QueryBuilderError;

pub(crate) use self::private::SetAutoTypeHelper;

impl<T: QuerySource, U> UpdateStatement<T, U, SetNotCalled> {
    pub(crate) fn new(target: UpdateTarget<T, U>) -> Self {
        UpdateStatement {
            from_clause: target.table.from_clause(),
            where_clause: target.where_clause,
            set_clause: SetClause::Immediate,
            values: SetNotCalled,
            returning: NoReturningClause,
        }
    }

    /// Provides the `SET` clause of the `UPDATE` statement.
    ///
    /// See [`update`](crate::update()) for usage examples, or [the update
    /// guide](https://diesel.rs/guides/all-about-updates/) for a more exhaustive
    /// set of examples.
    pub fn set<V>(self, values: V) -> crate::dsl::Set<Self, V>
    where
        T: Table,
        V: changeset::AsChangeset<Target = T>,
        UpdateStatement<T, U, V::Changeset>: AsQuery,
    {
        UpdateStatement {
            from_clause: self.from_clause,
            where_clause: self.where_clause,
            set_clause: <V as AsChangeset>::SET_CLAUSE,
            values: values.as_changeset(),
            returning: self.returning,
        }
    }
}

#[derive(Clone, Debug)]
#[must_use = "Queries are only executed when calling `load`, `get_result` or similar."]
/// Represents a complete `UPDATE` statement.
///
/// See [`update`](crate::update()) for usage examples, or [the update
/// guide](https://diesel.rs/guides/all-about-updates/) for a more exhaustive
/// set of examples.
pub struct UpdateStatement<T: QuerySource, U, V = SetNotCalled, Ret = NoReturningClause> {
    from_clause: T::FromClause,
    where_clause: U,
    set_clause: SetClause,
    values: V,
    returning: Ret,
}

/// An `UPDATE` statement with a boxed `WHERE` clause.
pub type BoxedUpdateStatement<'a, DB, T, V = SetNotCalled, Ret = NoReturningClause> =
    UpdateStatement<T, BoxedWhereClause<'a, DB>, V, Ret>;

impl<T: QuerySource, U, V, Ret> UpdateStatement<T, U, V, Ret> {
    /// 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
    /// `update(table.filter(x))` and `update(table).filter(x)`.
    ///
    /// # Example
    ///
    /// ```rust
    /// # include!("../../doctest_setup.rs");
    /// #
    /// # fn main() {
    /// #     use schema::users::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// let updated_rows = diesel::update(users)
    ///     .set(name.eq("Jim"))
    ///     .filter(name.eq("Sean"))
    ///     .execute(connection);
    /// assert_eq!(Ok(1), updated_rows);
    ///
    /// let expected_names = vec!["Jim".to_string(), "Tess".to_string()];
    /// let names = users.select(name).order(id).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 update 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
    /// # include!("../../doctest_setup.rs");
    /// #
    /// # fn main() {
    /// #     run_test().unwrap();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     use std::collections::HashMap;
    /// #     use schema::users::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// #     let mut params = HashMap::new();
    /// #     params.insert("tess_has_been_a_jerk", false);
    /// let mut query = diesel::update(users).set(name.eq("Jerk")).into_boxed();
    ///
    /// if !params["tess_has_been_a_jerk"] {
    ///     query = query.filter(name.ne("Tess"));
    /// }
    ///
    /// let updated_rows = query.execute(connection)?;
    /// assert_eq!(1, updated_rows);
    ///
    /// let expected_names = vec!["Jerk", "Tess"];
    /// let names = users.select(name).order(id).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, V, Ret, Predicate> FilterDsl<Predicate> for UpdateStatement<T, U, V, Ret>
where
    T: QuerySource,
    U: WhereAnd<Predicate>,
    Predicate: AppearsOnTable<T>,
{
    type Output = UpdateStatement<T, U::Output, V, Ret>;

    fn filter(self, predicate: Predicate) -> Self::Output {
        UpdateStatement {
            from_clause: self.from_clause,
            where_clause: self.where_clause.and(predicate),
            set_clause: self.set_clause,
            values: self.values,
            returning: self.returning,
        }
    }
}

impl<'a, T, U, V, Ret, DB> BoxedDsl<'a, DB> for UpdateStatement<T, U, V, Ret>
where
    T: QuerySource,
    U: Into<BoxedWhereClause<'a, DB>>,
{
    type Output = BoxedUpdateStatement<'a, DB, T, V, Ret>;

    fn internal_into_boxed(self) -> Self::Output {
        UpdateStatement {
            from_clause: self.from_clause,
            where_clause: self.where_clause.into(),
            set_clause: self.set_clause,
            values: self.values,
            returning: self.returning,
        }
    }
}

impl<T, U, V, Ret, DB> QueryFragment<DB> for UpdateStatement<T, U, V, Ret>
where
    DB: Backend + DieselReserveSpecialization,
    T: Table,
    T::FromClause: QueryFragment<DB>,
    U: QueryFragment<DB>,
    V: QueryFragment<DB> + AllowFilterForUpdate<U>,
    Ret: QueryFragment<DB>,
{
    fn walk_ast<'b>(&'b self, mut out: AstPass<'_, 'b, DB>) -> QueryResult<()> {
        if self.values.is_noop(out.backend())? {
            return Err(QueryBuilderError(Box::new(EmptyChangeset)));
        }

        out.unsafe_to_cache_prepared();
        out.push_sql("UPDATE ");
        self.from_clause.walk_ast(out.reborrow())?;
        self.set_clause.walk_ast(out.reborrow())?;
        self.values.walk_ast(out.reborrow())?;
        self.where_clause.walk_ast(out.reborrow())?;
        self.returning.walk_ast(out.reborrow())?;
        Ok(())
    }
}

impl<T, U, V, Ret> QueryId for UpdateStatement<T, U, V, Ret>
where
    T: QuerySource,
{
    type QueryId = ();

    const HAS_STATIC_QUERY_ID: bool = false;
}

impl<T, U, V> AsQuery for UpdateStatement<T, U, V, NoReturningClause>
where
    T: Table,
    UpdateStatement<T, U, V, ReturningClause<T::AllColumns>>: Query,
    T::AllColumns: SelectableExpression<ReturningQuerySource<UpdateStmt, T>> + ValidGrouping<()>,
    <T::AllColumns as ValidGrouping<()>>::IsAggregate:
        MixedAggregates<is_aggregate::No, Output = is_aggregate::No>,
{
    type SqlType = <Self::Query as Query>::SqlType;
    type Query = UpdateStatement<T, U, V, ReturningClause<T::AllColumns>>;

    fn as_query(self) -> Self::Query {
        self.returning(T::all_columns())
    }
}

impl<T, U, V, Ret> Query for UpdateStatement<T, U, V, ReturningClause<Ret>>
where
    T: Table,
    Ret: SelectableExpression<ReturningQuerySource<UpdateStmt, T>> + ValidGrouping<()>,
    Ret::IsAggregate: MixedAggregates<is_aggregate::No, Output = is_aggregate::No>,
{
    type SqlType = <Ret as Expression>::SqlType;
}

impl<T: QuerySource, U, V, Ret> RunQueryDslSupport for UpdateStatement<T, U, V, Ret> {}

impl<T: QuerySource, U, V> UpdateStatement<T, U, V, NoReturningClause> {
    /// Specify what expression is returned after execution of the `update`.
    /// # Examples
    ///
    /// ### Updating a single record:
    ///
    /// ```rust
    /// # include!("../../doctest_setup.rs");
    /// #
    /// # #[cfg(feature = "postgres")]
    /// # fn main() {
    /// #     use schema::users::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// let updated_name = diesel::update(users.filter(id.eq(1)))
    ///     .set(name.eq("Dean"))
    ///     .returning(name)
    ///     .get_result(connection);
    /// assert_eq!(Ok("Dean".to_string()), updated_name);
    /// # }
    /// # #[cfg(not(feature = "postgres"))]
    /// # fn main() {}
    /// ```
    ///
    /// ### Returning the pre-update value (PostgreSQL 18+):
    ///
    /// `RETURNING old.col` — exposed via [`diesel::pg::returning::old()`] —
    /// returns the value of the column **before** the update was applied.
    /// This requires PostgreSQL 18 or newer.
    ///
    /// ```rust
    /// # include!("../../doctest_setup.rs");
    /// #
    /// # #[cfg(feature = "postgres")]
    /// # fn main() {
    /// #     use schema::users::dsl::*;
    /// #     use diesel::pg::returning::old;
    /// #     let connection = &mut establish_connection();
    /// #     // `RETURNING old.col` requires PostgreSQL 18+
    /// #     let pg_version: i32 = diesel::dsl::sql::<diesel::sql_types::Integer>(
    /// #         "SELECT current_setting('server_version_num')::int",
    /// #     ).get_result(connection).unwrap();
    /// #     if pg_version < 180000 { return; }
    /// let was_and_now = diesel::update(users.filter(id.eq(1)))
    ///     .set(name.eq("Dean"))
    ///     .returning((old(name), name))
    ///     .get_result::<(String, String)>(connection);
    /// assert_eq!(Ok(("Sean".to_string(), "Dean".to_string())), was_and_now);
    /// # }
    /// # #[cfg(not(feature = "postgres"))]
    /// # fn main() {}
    /// ```
    pub fn returning<E>(self, returns: E) -> UpdateStatement<T, U, V, ReturningClause<E>>
    where
        T: Table,
        UpdateStatement<T, U, V, ReturningClause<E>>: Query,
    {
        UpdateStatement {
            from_clause: self.from_clause,
            where_clause: self.where_clause,
            set_clause: self.set_clause,
            values: self.values,
            returning: ReturningClause(returns),
        }
    }
}

/// Indicates that you have not yet called `.set` on an update statement
#[derive(Debug, Clone, Copy)]
pub struct SetNotCalled;

pub(crate) mod private {
    use crate::backend::Backend;
    use crate::query_builder::where_clause::{BoxedWhereClause, NoWhereClause, WhereClause};

    use super::changeset::Assign;

    /// Helper trait for `#[auto_type]`
    ///
    /// This trait allows inferring the return type of `UpdateStatement::set` and
    /// `IncompleteDoUpdate::set` (via `IntoUpdateTarget`). It is used to define the
    /// `Set` type alias in `diesel::dsl`.
    #[allow(unreachable_pub)]
    pub trait SetAutoTypeHelper<Changes> {
        type Out;
    }

    impl<T, W, Changes> SetAutoTypeHelper<Changes> for crate::query_builder::UpdateStatement<T, W>
    where
        T: crate::QuerySource,
        Changes: crate::AsChangeset,
    {
        type Out = crate::query_builder::UpdateStatement<T, W, Changes::Changeset>;
    }

    /// A helper trait to mark values clauses as compatible with a given filter syntax
    #[diagnostic::on_unimplemented(
        message = "cannot apply a `WHERE` clause to batch updates",
        note = "the information about which rows to update are provided as part of the values"
    )]
    pub trait AllowFilterForUpdate<P> {}

    impl<U> AllowFilterForUpdate<NoWhereClause> for U {}

    impl<W, C, B> AllowFilterForUpdate<WhereClause<W>> for Assign<C, B> {}
    impl<W, T> AllowFilterForUpdate<WhereClause<W>> for Option<T> where
        T: AllowFilterForUpdate<WhereClause<W>>
    {
    }

    impl<'a, DB, C, B> AllowFilterForUpdate<BoxedWhereClause<'a, DB>> for Assign<C, B> where DB: Backend {}
    impl<'a, DB, T> AllowFilterForUpdate<BoxedWhereClause<'a, DB>> for Option<T>
    where
        DB: Backend,
        T: AllowFilterForUpdate<BoxedWhereClause<'a, DB>>,
    {
    }
}

/// Determines when the `SET` part of an update statement will be added to the sql.
///
/// Usual single row updates default to [SetClause::Immediate]. Batch row updates
/// will use [SetClause::Delegated].
///
/// - [SetClause::Immediate]
///   will add `SET` right after the [UpdateStatement::from_clause] `QueryFragment`. \
///   `Update users SET ... ;`
/// - [SetClause::Delegated]
///   hands over the control of adding `SET` to [UpdateStatement::values] `QueryFragment`. \
///   `Update users ... SET ... ; ` will then be permitted.  \
///   Batch update for mysql requires this behavior.
#[derive(Clone, Copy, Debug)]
pub enum SetClause {
    Immediate,
    Delegated,
}

impl<DB> QueryFragment<DB> for SetClause
where
    DB: Backend,
{
    fn walk_ast<'b>(&'b self, mut out: AstPass<'_, 'b, DB>) -> QueryResult<()> {
        if let SetClause::Immediate = self {
            out.push_sql(" SET ");
        }
        Ok(())
    }
}