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
separately. 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
source§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 instrumentation(&mut self) -> &mut dyn Instrumentation
fn instrumentation(&mut self) -> &mut dyn Instrumentation
source§fn set_instrumentation(&mut self, instrumentation: impl Instrumentation)
fn set_instrumentation(&mut self, instrumentation: impl Instrumentation)
Instrumentation
implementation for this connectionsource§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<T, A> ExecuteCopyFromDsl<PgConnection> for CopyFromQuery<T, A>where
A: CopyFromExpression<T>,
impl<T, A> ExecuteCopyFromDsl<PgConnection> for CopyFromQuery<T, A>where
A: CopyFromExpression<T>,
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§type Cursor<'conn, 'query> = <PgConnection as PgLoadingMode<B>>::Cursor<'conn, 'query>
type Cursor<'conn, 'query> = <PgConnection as PgLoadingMode<B>>::Cursor<'conn, 'query>
LoadConnection::load
Read moresource§type Row<'conn, 'query> = <PgConnection as PgLoadingMode<B>>::Row<'conn, 'query>
type Row<'conn, 'query> = <PgConnection as PgLoadingMode<B>>::Row<'conn, 'query>
Iterator::Item
for the iterator implementation
of LoadConnection::Cursor