Struct Map

pub struct Map<'q, DB, F, A>
where
    DB: Database,
{ /* private fields */ }

SQL query that will map its results to owned Rust types.

Returned by Query::try_map, query!(), etc. Has most of the same methods as Query but the return types are changed to reflect the mapping. However, there is no equivalent of Query::execute as it doesn’t make sense to map the result type and then ignore it.

Query::bind is also omitted; stylistically we recommend placing your .bind() calls before .try_map(). This is also to prevent adding superfluous binds to the result of query!() et al.

Implementations

impl<'q, DB, F, O, A> Map<'q, DB, F, A>

where DB: Database, F: FnMut(<DB as Database>::Row) -> Result<O, Error> + Send, O: Send + Unpin, A: 'q + Send + IntoArguments<'q, DB>,

pub fn map<G, P>( self, g: G, ) -> Map<'q, DB, impl FnMut(<DB as Database>::Row) + Send, A>

where G: FnMut(O) -> P + Send, P: Unpin,

Map each row in the result to another type.

See try_map for a fallible version of this method.

The query_as method will construct a mapped query using a FromRow implementation.

pub fn try_map<G, P>( self, g: G, ) -> Map<'q, DB, impl FnMut(<DB as Database>::Row) + Send, A>

where G: FnMut(O) -> Result<P, Error> + Send, P: Unpin,

Map each row in the result to another type.

The query_as method will construct a mapped query using a FromRow implementation.

pub fn fetch<'e, 'c, E>( self, executor: E, ) -> Pin<Box<dyn Stream<Item = Result<O, Error>> + Send + 'e>>

where 'c: 'e, 'q: 'e, E: 'e + Executor<'c, Database = DB>, DB: 'e, F: 'e, O: 'e,

Execute the query and return the generated results as a stream.

pub fn fetch_many<'e, 'c, E>( self, executor: E, ) -> Pin<Box<dyn Stream<Item = Result<Either<<DB as Database>::QueryResult, O>, Error>> + Send + 'e>>

where 'c: 'e, 'q: 'e, E: 'e + Executor<'c, Database = DB>, DB: 'e, F: 'e, O: 'e,

Execute multiple queries and return the generated results as a stream from each query, in a stream.

pub async fn fetch_all<'e, 'c, E>(self, executor: E) -> Result<Vec<O>, Error>

where 'c: 'e, 'q: 'e, E: 'e + Executor<'c, Database = DB>, DB: 'e, F: 'e, O: 'e,

Execute the query and return all the generated results, collected into a Vec.

pub async fn fetch_one<'e, 'c, E>(self, executor: E) -> Result<O, Error>

where 'c: 'e, 'q: 'e, E: 'e + Executor<'c, Database = DB>, DB: 'e, F: 'e, O: 'e,

Execute the query and returns exactly one row.

pub async fn fetch_optional<'e, 'c, E>( self, executor: E, ) -> Result<Option<O>, Error>

where 'c: 'e, 'q: 'e, E: 'e + Executor<'c, Database = DB>, DB: 'e, F: 'e, O: 'e,

Execute the query and returns at most one row.

Trait Implementations

impl<'q, DB, F, A> Execute<'q, DB> for Map<'q, DB, F, A>

where F: Send, A: Send + IntoArguments<'q, DB>, DB: Database,

fn sql(&self) -> &'q str

Gets the SQL that will be executed.

fn statement(&self) -> Option<&<DB as HasStatement<'q>>::Statement>

Gets the previously cached statement, if available.

fn take_arguments(&mut self) -> Option<<DB as HasArguments<'q>>::Arguments>

Returns the arguments to be bound against the query string.

fn persistent(&self) -> bool

Returns true if the statement should be cached.