Trait diesel::query_builder::QueryId

pub trait QueryId {
    type QueryId: Any;

    const HAS_STATIC_QUERY_ID: bool;
    fn query_id() -> Option<TypeId> { ... }
}

Uniquely identifies queries by their type for the purpose of prepared statement caching.

All types which implement QueryFragment should also implement this trait (It is not an actual supertrait of QueryFragment for boxing purposes).

See the documentation of the QueryId type and HAS_STATIC_QUERY_ID for more details.

Deriving

This trait can be automatically derived by Diesel. For example, given this struct:

#[derive(QueryId)]
pub struct And<Left, Right> {
    left: Left,
    right: Right,
}

the following implementation will be generated

impl<Left, Right> QueryId for And<Left, Right>
where
    Left: QueryId,
    Right: QueryId,
{
    type QueryId = And<Left::QueryId, Right::QueryId>;

    const HAS_STATIC_QUERY_ID: bool = Left::HAS_STATIC_QUERY_ID && Right::HAS_STATIC_QUERY_ID;
}

If the SQL generated by a struct is not uniquely identifiable by its type, meaning that HAS_STATIC_QUERY_ID should always be false, you should not derive this trait. In that case you should manually implement it instead.

Associated Types

type QueryId: Any

A type which uniquely represents Self in a SQL query.

Typically this will be a re-construction of Self using the QueryId type of each of your type parameters. For example, the type And<Left, Right> would have type QueryId = And<Left::QueryId, Right::QueryId>.

The exception to this is when one of your type parameters does not affect whether the same prepared statement can be used or not. For example, a bind parameter is represented as Bound<SqlType, RustType>. The actual Rust type we are serializing does not matter for the purposes of prepared statement reuse, but a query which has identical SQL but different types for its bind parameters requires a new prepared statement. For this reason, Bound would have type QueryId = Bound<SqlType::QueryId, ()>.

If HAS_STATIC_QUERY_ID is false, you can put any type here (typically ()).

Loading content...

Associated Constants

const HAS_STATIC_QUERY_ID: bool

Can the SQL generated by Self be uniquely identified by its type?

Typically this question can be answered by looking at whether unsafe_to_cache_prepared is called in your implementation of QueryFragment::walk_ast. In Diesel itself, the only type which has false here, but is potentially safe to store in the prepared statement cache is a boxed query.

Loading content...

Provided methods

fn query_id() -> Option<TypeId>

Returns the type id of Self::QueryId if Self::HAS_STATIC_QUERY_ID. Returns None otherwise.

You should never need to override this method.

Loading content...

Implementations on Foreign Types

impl QueryId for ()

type QueryId = ()

const HAS_STATIC_QUERY_ID: bool

impl<T: QueryId + ?Sized> QueryId for Box<T>

type QueryId = T::QueryId

const HAS_STATIC_QUERY_ID: bool

impl<'a, T: QueryId + ?Sized> QueryId for &'a T

type QueryId = T::QueryId

const HAS_STATIC_QUERY_ID: bool

impl<A: QueryId> QueryId for (A,)

type QueryId = (A::QueryId,)

const HAS_STATIC_QUERY_ID: bool

impl<A: QueryId, B: QueryId> QueryId for (A, B)

type QueryId = (A::QueryId, B::QueryId)

const HAS_STATIC_QUERY_ID: bool

impl<A: QueryId, B: QueryId, C: QueryId> QueryId for (A, B, C)

type QueryId = (A::QueryId, B::QueryId, C::QueryId)

const HAS_STATIC_QUERY_ID: bool

impl<A: QueryId, B: QueryId, C: QueryId, D: QueryId> QueryId for (A, B, C, D)

type QueryId = (A::QueryId, B::QueryId, C::QueryId, D::QueryId)

const HAS_STATIC_QUERY_ID: bool

impl<A: QueryId, B: QueryId, C: QueryId, D: QueryId, E: QueryId> QueryId for (A, B, C, D, E)

type QueryId = (A::QueryId, B::QueryId, C::QueryId, D::QueryId, E::QueryId)

const HAS_STATIC_QUERY_ID: bool

impl<A: QueryId, B: QueryId, C: QueryId, D: QueryId, E: QueryId, F: QueryId> QueryId for (A, B, C, D, E, F)

type QueryId = (A::QueryId, B::QueryId, C::QueryId, D::QueryId, E::QueryId, F::QueryId)

const HAS_STATIC_QUERY_ID: bool

impl<A: QueryId, B: QueryId, C: QueryId, D: QueryId, E: QueryId, F: QueryId, G: QueryId> QueryId for (A, B, C, D, E, F, G)

type QueryId = (A::QueryId, B::QueryId, C::QueryId, D::QueryId, E::QueryId, F::QueryId, G::QueryId)

const HAS_STATIC_QUERY_ID: bool

impl<A: QueryId, B: QueryId, C: QueryId, D: QueryId, E: QueryId, F: QueryId, G: QueryId, H: QueryId> QueryId for (A, B, C, D, E, F, G, H)

type QueryId = (A::QueryId, B::QueryId, C::QueryId, D::QueryId, E::QueryId, F::QueryId, G::QueryId, H::QueryId)

const HAS_STATIC_QUERY_ID: bool

impl<A: QueryId, B: QueryId, C: QueryId, D: QueryId, E: QueryId, F: QueryId, G: QueryId, H: QueryId, I: QueryId> QueryId for (A, B, C, D, E, F, G, H, I)

type QueryId = (A::QueryId, B::QueryId, C::QueryId, D::QueryId, E::QueryId, F::QueryId, G::QueryId, H::QueryId, I::QueryId)

const HAS_STATIC_QUERY_ID: bool

impl<A: QueryId, B: QueryId, C: QueryId, D: QueryId, E: QueryId, F: QueryId, G: QueryId, H: QueryId, I: QueryId, J: QueryId> QueryId for (A, B, C, D, E, F, G, H, I, J)

type QueryId = (A::QueryId, B::QueryId, C::QueryId, D::QueryId, E::QueryId, F::QueryId, G::QueryId, H::QueryId, I::QueryId, J::QueryId)

const HAS_STATIC_QUERY_ID: bool

impl<A: QueryId, B: QueryId, C: QueryId, D: QueryId, E: QueryId, F: QueryId, G: QueryId, H: QueryId, I: QueryId, J: QueryId, K: QueryId> QueryId for (A, B, C, D, E, F, G, H, I, J, K)

type QueryId = (A::QueryId, B::QueryId, C::QueryId, D::QueryId, E::QueryId, F::QueryId, G::QueryId, H::QueryId, I::QueryId, J::QueryId, K::QueryId)

const HAS_STATIC_QUERY_ID: bool

impl<A: QueryId, B: QueryId, C: QueryId, D: QueryId, E: QueryId, F: QueryId, G: QueryId, H: QueryId, I: QueryId, J: QueryId, K: QueryId, L: QueryId> QueryId for (A, B, C, D, E, F, G, H, I, J, K, L)

type QueryId = (A::QueryId, B::QueryId, C::QueryId, D::QueryId, E::QueryId, F::QueryId, G::QueryId, H::QueryId, I::QueryId, J::QueryId, K::QueryId, L::QueryId)

const HAS_STATIC_QUERY_ID: bool

impl<A: QueryId, B: QueryId, C: QueryId, D: QueryId, E: QueryId, F: QueryId, G: QueryId, H: QueryId, I: QueryId, J: QueryId, K: QueryId, L: QueryId, M: QueryId> QueryId for (A, B, C, D, E, F, G, H, I, J, K, L, M)

type QueryId = (A::QueryId, B::QueryId, C::QueryId, D::QueryId, E::QueryId, F::QueryId, G::QueryId, H::QueryId, I::QueryId, J::QueryId, K::QueryId, L::QueryId, M::QueryId)

const HAS_STATIC_QUERY_ID: bool

impl<A: QueryId, B: QueryId, C: QueryId, D: QueryId, E: QueryId, F: QueryId, G: QueryId, H: QueryId, I: QueryId, J: QueryId, K: QueryId, L: QueryId, M: QueryId, N: QueryId> QueryId for (A, B, C, D, E, F, G, H, I, J, K, L, M, N)

type QueryId = (A::QueryId, B::QueryId, C::QueryId, D::QueryId, E::QueryId, F::QueryId, G::QueryId, H::QueryId, I::QueryId, J::QueryId, K::QueryId, L::QueryId, M::QueryId, N::QueryId)

const HAS_STATIC_QUERY_ID: bool

impl<A: QueryId, B: QueryId, C: QueryId, D: QueryId, E: QueryId, F: QueryId, G: QueryId, H: QueryId, I: QueryId, J: QueryId, K: QueryId, L: QueryId, M: QueryId, N: QueryId, O: QueryId> QueryId for (A, B, C, D, E, F, G, H, I, J, K, L, M, N, O)

type QueryId = (A::QueryId, B::QueryId, C::QueryId, D::QueryId, E::QueryId, F::QueryId, G::QueryId, H::QueryId, I::QueryId, J::QueryId, K::QueryId, L::QueryId, M::QueryId, N::QueryId, O::QueryId)

const HAS_STATIC_QUERY_ID: bool

impl<A: QueryId, B: QueryId, C: QueryId, D: QueryId, E: QueryId, F: QueryId, G: QueryId, H: QueryId, I: QueryId, J: QueryId, K: QueryId, L: QueryId, M: QueryId, N: QueryId, O: QueryId, P: QueryId> QueryId for (A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P)

type QueryId = (A::QueryId, B::QueryId, C::QueryId, D::QueryId, E::QueryId, F::QueryId, G::QueryId, H::QueryId, I::QueryId, J::QueryId, K::QueryId, L::QueryId, M::QueryId, N::QueryId, O::QueryId, P::QueryId)

const HAS_STATIC_QUERY_ID: bool

Loading content...

Implementors

impl QueryId for now

type QueryId = now

const HAS_STATIC_QUERY_ID: bool

impl QueryId for Datetime

type QueryId = Datetime

const HAS_STATIC_QUERY_ID: bool

impl QueryId for Cidr

type QueryId = Cidr

const HAS_STATIC_QUERY_ID: bool

impl QueryId for Inet

type QueryId = Inet

const HAS_STATIC_QUERY_ID: bool

impl QueryId for Json

type QueryId = Json

const HAS_STATIC_QUERY_ID: bool

impl QueryId for Jsonb

type QueryId = Jsonb

const HAS_STATIC_QUERY_ID: bool

impl QueryId for MacAddr

type QueryId = MacAddr

const HAS_STATIC_QUERY_ID: bool

impl QueryId for Money

type QueryId = Money

const HAS_STATIC_QUERY_ID: bool

impl QueryId for Oid

type QueryId = Oid

const HAS_STATIC_QUERY_ID: bool

impl QueryId for Timestamptz

type QueryId = Timestamptz

const HAS_STATIC_QUERY_ID: bool

impl QueryId for Uuid

type QueryId = Uuid

const HAS_STATIC_QUERY_ID: bool

impl QueryId for SqlQuery

type QueryId = ()

const HAS_STATIC_QUERY_ID: bool

impl QueryId for BigInt

type QueryId = BigInt

const HAS_STATIC_QUERY_ID: bool

impl QueryId for Binary

type QueryId = Binary

const HAS_STATIC_QUERY_ID: bool

impl QueryId for Bool

type QueryId = Bool

const HAS_STATIC_QUERY_ID: bool

impl QueryId for Date

type QueryId = Date

const HAS_STATIC_QUERY_ID: bool

impl QueryId for Double

type QueryId = Double

const HAS_STATIC_QUERY_ID: bool

impl QueryId for Float

type QueryId = Float

const HAS_STATIC_QUERY_ID: bool

impl QueryId for Integer

type QueryId = Integer

const HAS_STATIC_QUERY_ID: bool

impl QueryId for Interval

type QueryId = Interval

const HAS_STATIC_QUERY_ID: bool

impl QueryId for Numeric

type QueryId = Numeric

const HAS_STATIC_QUERY_ID: bool

impl QueryId for SmallInt

type QueryId = SmallInt

const HAS_STATIC_QUERY_ID: bool

impl QueryId for Text

type QueryId = Text

const HAS_STATIC_QUERY_ID: bool

impl QueryId for Time

type QueryId = Time

const HAS_STATIC_QUERY_ID: bool

impl QueryId for Timestamp

type QueryId = Timestamp

const HAS_STATIC_QUERY_ID: bool

impl QueryId for TinyInt

type QueryId = TinyInt

const HAS_STATIC_QUERY_ID: bool

impl<'a, QS, ST, DB> QueryId for dyn BoxableExpression<QS, DB, SqlType = ST> + 'a

type QueryId = ()

const HAS_STATIC_QUERY_ID: bool

impl<DB> QueryId for dyn QueryFragment<DB>

type QueryId = ()

const HAS_STATIC_QUERY_ID: bool

impl<Query: QueryId, Value: QueryId> QueryId for UncheckedBind<Query, Value>

type QueryId = UncheckedBind<<Query as QueryId>::QueryId, <Value as QueryId>::QueryId>

const HAS_STATIC_QUERY_ID: bool

impl<ST, T> QueryId for SqlLiteral<ST, T>

type QueryId = ()

const HAS_STATIC_QUERY_ID: bool

impl<ST: QueryId> QueryId for Unsigned<ST>

type QueryId = Unsigned<<ST as QueryId>::QueryId>

const HAS_STATIC_QUERY_ID: bool

impl<ST: QueryId> QueryId for Array<ST>

type QueryId = Array<<ST as QueryId>::QueryId>

const HAS_STATIC_QUERY_ID: bool

impl<ST: QueryId> QueryId for Range<ST>

type QueryId = Range<<ST as QueryId>::QueryId>

const HAS_STATIC_QUERY_ID: bool

impl<ST: QueryId> QueryId for Record<ST>

type QueryId = Record<<ST as QueryId>::QueryId>

const HAS_STATIC_QUERY_ID: bool

impl<T> QueryId for Nullable<T> where
    T: QueryId + NotNull, 

type QueryId = T::QueryId

const HAS_STATIC_QUERY_ID: bool

impl<T, U, Op, Ret> QueryId for InsertStatement<T, U, Op, Ret>

type QueryId = ()

const HAS_STATIC_QUERY_ID: bool

impl<T, U, V, Ret> QueryId for UpdateStatement<T, U, V, Ret>

type QueryId = ()

const HAS_STATIC_QUERY_ID: bool

impl<T: QueryId> QueryId for DistinctOnClause<T>

type QueryId = DistinctOnClause<<T as QueryId>::QueryId>

const HAS_STATIC_QUERY_ID: bool

impl<T: QueryId, U: QueryId, Ret: QueryId> QueryId for DeleteStatement<T, U, Ret>

type QueryId = DeleteStatement<<T as QueryId>::QueryId, <U as QueryId>::QueryId, <Ret as QueryId>::QueryId>

const HAS_STATIC_QUERY_ID: bool

Loading content...