Struct diesel::prelude::PgConnection
source · pub struct PgConnection { /* private fields */ }
Expand description
The connection string expected by PgConnection::establish
should be a PostgreSQL connection string, as documented at
https://www.postgresql.org/docs/9.4/static/libpq-connect.html#LIBPQ-CONNSTRING
§Supported loading model implementations
If you are unsure which loading mode is the correct one for your application,
you likely want to use the DefaultLoadingMode
as that one offers
generally better performance.
Due to the fact that PgConnection
supports multiple loading modes
it is required to always specify the used loading mode
when calling RunQueryDsl::load_iter
§DefaultLoadingMode
By using this mode PgConnection
defaults to loading all response values at once
and only performs deserialization afterward for the DefaultLoadingMode
.
Generally this mode will be more performant as it.
This loading mode allows users to perform hold more than one iterator at once using the same connection:
use diesel::connection::DefaultLoadingMode;
let iter1 = users::table.load_iter::<(i32, String), DefaultLoadingMode>(connection)?;
let iter2 = users::table.load_iter::<(i32, String), DefaultLoadingMode>(connection)?;
for r in iter1 {
let (id, name) = r?;
println!("Id: {} Name: {}", id, name);
}
for r in iter2 {
let (id, name) = r?;
println!("Id: {} Name: {}", id, name);
}
§PgRowByRowLoadingMode
By using this mode PgConnection
defaults to loading each row of the result set
sepreatly. This might be desired for huge result sets.
This loading mode prevents creating more than one iterator at once using the same connection. The following code is not allowed:
use diesel::pg::PgRowByRowLoadingMode;
let iter1 = users::table.load_iter::<(i32, String), PgRowByRowLoadingMode>(connection)?;
// creating a second iterator generates an compiler error
let iter2 = users::table.load_iter::<(i32, String), PgRowByRowLoadingMode>(connection)?;
for r in iter1 {
let (id, name) = r?;
println!("Id: {} Name: {}", id, name);
}
for r in iter2 {
let (id, name) = r?;
println!("Id: {} Name: {}", id, name);
}
Implementations§
source§impl PgConnection
impl PgConnection
sourcepub fn build_transaction(&mut self) -> TransactionBuilder<'_, Self>
pub fn build_transaction(&mut self) -> TransactionBuilder<'_, Self>
Build a transaction, specifying additional details such as isolation level
See TransactionBuilder
for more examples.
conn.build_transaction()
.read_only()
.serializable()
.deferrable()
.run(|conn| Ok(()))
Trait Implementations§
source§impl Connection for PgConnection
impl Connection for PgConnection
§type TransactionManager = AnsiTransactionManager
type TransactionManager = AnsiTransactionManager
source§fn establish(database_url: &str) -> ConnectionResult<PgConnection>
fn establish(database_url: &str) -> ConnectionResult<PgConnection>
source§fn execute_returning_count<T>(&mut self, source: &T) -> QueryResult<usize>
fn execute_returning_count<T>(&mut self, source: &T) -> QueryResult<usize>
source§fn transaction_state(&mut self) -> &mut AnsiTransactionManagerwhere
Self: Sized,
fn transaction_state(&mut self) -> &mut AnsiTransactionManagerwhere
Self: Sized,
source§fn transaction<T, E, F>(&mut self, f: F) -> Result<T, E>
fn transaction<T, E, F>(&mut self, f: F) -> Result<T, E>
source§fn begin_test_transaction(&mut self) -> QueryResult<()>
fn begin_test_transaction(&mut self) -> QueryResult<()>
source§impl<'conn, 'query> ConnectionGatWorkaround<'conn, 'query, Pg> for PgConnection
impl<'conn, 'query> ConnectionGatWorkaround<'conn, 'query, Pg> for PgConnection
§type Cursor = Cursor
type Cursor = Cursor
LoadConnection::load
Read more§type Row = PgRow
type Row = PgRow
Iterator::Item
for the iterator implementation
of ConnectionGatWorkaround::Cursor
source§impl<'conn, 'query> ConnectionGatWorkaround<'conn, 'query, Pg, PgRowByRowLoadingMode> for PgConnection
impl<'conn, 'query> ConnectionGatWorkaround<'conn, 'query, Pg, PgRowByRowLoadingMode> for PgConnection
§type Cursor = RowByRowCursor<'conn>
type Cursor = RowByRowCursor<'conn>
LoadConnection::load
Read more§type Row = PgRow
type Row = PgRow
Iterator::Item
for the iterator implementation
of ConnectionGatWorkaround::Cursor
source§impl GetPgMetadataCache for PgConnection
impl GetPgMetadataCache for PgConnection
source§fn get_metadata_cache(&mut self) -> &mut PgMetadataCache
fn get_metadata_cache(&mut self) -> &mut PgMetadataCache
PgMetadataCache
source§impl<B> LoadConnection<B> for PgConnectionwhere
Self: PgLoadingMode<B>,
impl<B> LoadConnection<B> for PgConnectionwhere
Self: PgLoadingMode<B>,
source§fn load<'conn, 'query, T>(
&'conn mut self,
source: T,
) -> QueryResult<LoadRowIter<'conn, 'query, Self, Self::Backend, B>>where
T: Query + QueryFragment<Self::Backend> + QueryId + 'query,
Self::Backend: QueryMetadata<T::SqlType>,
fn load<'conn, 'query, T>(
&'conn mut self,
source: T,
) -> QueryResult<LoadRowIter<'conn, 'query, Self, Self::Backend, B>>where
T: Query + QueryFragment<Self::Backend> + QueryId + 'query,
Self::Backend: QueryMetadata<T::SqlType>,
source§impl MigrationConnection for PgConnection
impl MigrationConnection for PgConnection
source§impl SimpleConnection for PgConnection
impl SimpleConnection for PgConnection
source§fn batch_execute(&mut self, query: &str) -> QueryResult<()>
fn batch_execute(&mut self, query: &str) -> QueryResult<()>
source§impl<'b, Changes, Output> UpdateAndFetchResults<Changes, Output> for PgConnectionwhere
Changes: Copy + AsChangeset<Target = <Changes as HasTable>::Table> + IntoUpdateTarget,
Update<Changes, Changes>: LoadQuery<'b, PgConnection, Output>,
<Changes::Table as Table>::AllColumns: ValidGrouping<()>,
<<Changes::Table as Table>::AllColumns as ValidGrouping<()>>::IsAggregate: MixedAggregates<No, Output = No>,
impl<'b, Changes, Output> UpdateAndFetchResults<Changes, Output> for PgConnectionwhere
Changes: Copy + AsChangeset<Target = <Changes as HasTable>::Table> + IntoUpdateTarget,
Update<Changes, Changes>: LoadQuery<'b, PgConnection, Output>,
<Changes::Table as Table>::AllColumns: ValidGrouping<()>,
<<Changes::Table as Table>::AllColumns as ValidGrouping<()>>::IsAggregate: MixedAggregates<No, Output = No>,
source§fn update_and_fetch(&mut self, changeset: Changes) -> QueryResult<Output>
fn update_and_fetch(&mut self, changeset: Changes) -> QueryResult<Output>
impl Send for PgConnection
Auto Trait Implementations§
impl Freeze for PgConnection
impl RefUnwindSafe for PgConnection
impl !Sync for PgConnection
impl Unpin for PgConnection
impl UnwindSafe for PgConnection
Blanket Implementations§
source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
source§impl<C> BoxableConnection<<C as Connection>::Backend> for Cwhere
C: Connection + Any,
impl<C> BoxableConnection<<C as Connection>::Backend> for Cwhere
C: Connection + Any,
source§impl<T> IntoSql for T
impl<T> IntoSql for T
source§impl<T> PgMetadataLookup for T
impl<T> PgMetadataLookup for T
source§fn lookup_type(
&mut self,
type_name: &str,
schema: Option<&str>,
) -> PgTypeMetadata
fn lookup_type( &mut self, type_name: &str, schema: Option<&str>, ) -> PgTypeMetadata
type_name
Read more