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//! Provides types and functions related to working with PostgreSQL
//!
//! Much of this module is re-exported from database agnostic locations.
//! However, if you are writing code specifically to extend Diesel on
//! PostgreSQL, you may need to work with this module directly.
use self::error_helper::ErrorHelper;
use self::row::PgRow;
use self::serialize::ToSqlHelper;
use crate::stmt_cache::{PrepareCallback, StmtCache};
use crate::{AnsiTransactionManager, AsyncConnection, SimpleAsyncConnection};
use diesel::connection::statement_cache::PrepareForCache;
use diesel::pg::{
FailedToLookupTypeError, PgMetadataCache, PgMetadataCacheKey, PgMetadataLookup, PgTypeMetadata,
};
use diesel::query_builder::bind_collector::RawBytesBindCollector;
use diesel::query_builder::{AsQuery, QueryFragment, QueryId};
use diesel::{ConnectionError, ConnectionResult, QueryResult};
use futures::future::BoxFuture;
use futures::lock::Mutex;
use futures::stream::{BoxStream, TryStreamExt};
use futures::{Future, FutureExt, StreamExt};
use std::borrow::Cow;
use std::sync::Arc;
use tokio_postgres::types::ToSql;
use tokio_postgres::types::Type;
use tokio_postgres::Statement;
pub use self::transaction_builder::TransactionBuilder;
mod error_helper;
mod row;
mod serialize;
mod transaction_builder;
/// A connection to a PostgreSQL database.
///
/// Connection URLs should be in the form
/// `postgres://[user[:password]@]host/database_name`
///
/// Checkout the documentation of the [tokio_postgres]
/// crate for details about the format
///
/// [tokio_postgres]: https://docs.rs/tokio-postgres/0.7.6/tokio_postgres/config/struct.Config.html#url
///
/// This connection supports *pipelined* requests. Pipelining can improve performance in use cases in which multiple,
/// independent queries need to be executed. In a traditional workflow, each query is sent to the server after the
/// previous query completes. In contrast, pipelining allows the client to send all of the queries to the server up
/// front, minimizing time spent by one side waiting for the other to finish sending data:
///
/// ```not_rust
/// Sequential Pipelined
/// | Client | Server | | Client | Server |
/// |----------------|-----------------| |----------------|-----------------|
/// | send query 1 | | | send query 1 | |
/// | | process query 1 | | send query 2 | process query 1 |
/// | receive rows 1 | | | send query 3 | process query 2 |
/// | send query 2 | | | receive rows 1 | process query 3 |
/// | | process query 2 | | receive rows 2 | |
/// | receive rows 2 | | | receive rows 3 | |
/// | send query 3 | |
/// | | process query 3 |
/// | receive rows 3 | |
/// ```
///
/// In both cases, the PostgreSQL server is executing the queries **sequentially** - pipelining just allows both sides of
/// the connection to work concurrently when possible.
///
/// Pipelining happens automatically when futures are polled concurrently (for example, by using the futures `join`
/// combinator):
///
/// ```rust
/// # include!("../doctest_setup.rs");
/// #
/// # #[tokio::main(flavor = "current_thread")]
/// # async fn main() {
/// # run_test().await.unwrap();
/// # }
/// #
/// # async fn run_test() -> QueryResult<()> {
/// # use diesel::sql_types::{Text, Integer};
/// # let conn = &mut establish_connection().await;
/// let q1 = diesel::select(1_i32.into_sql::<Integer>());
/// let q2 = diesel::select(2_i32.into_sql::<Integer>());
///
/// // construct multiple futures for different queries
/// let f1 = q1.get_result::<i32>(conn);
/// let f2 = q2.get_result::<i32>(conn);
///
/// // wait on both results
/// let res = futures::try_join!(f1, f2)?;
///
/// assert_eq!(res.0, 1);
/// assert_eq!(res.1, 2);
/// # Ok(())
/// # }
pub struct AsyncPgConnection {
conn: Arc<tokio_postgres::Client>,
stmt_cache: Arc<Mutex<StmtCache<diesel::pg::Pg, Statement>>>,
transaction_state: Arc<Mutex<AnsiTransactionManager>>,
metadata_cache: Arc<Mutex<Option<PgMetadataCache>>>,
}
#[async_trait::async_trait]
impl SimpleAsyncConnection for AsyncPgConnection {
async fn batch_execute(&mut self, query: &str) -> QueryResult<()> {
Ok(self.conn.batch_execute(query).await.map_err(ErrorHelper)?)
}
}
#[async_trait::async_trait]
impl AsyncConnection for AsyncPgConnection {
type LoadFuture<'conn, 'query> = BoxFuture<'query, QueryResult<Self::Stream<'conn, 'query>>>;
type ExecuteFuture<'conn, 'query> = BoxFuture<'query, QueryResult<usize>>;
type Stream<'conn, 'query> = BoxStream<'static, QueryResult<PgRow>>;
type Row<'conn, 'query> = PgRow;
type Backend = diesel::pg::Pg;
type TransactionManager = AnsiTransactionManager;
async fn establish(database_url: &str) -> ConnectionResult<Self> {
let (client, connection) = tokio_postgres::connect(database_url, tokio_postgres::NoTls)
.await
.map_err(ErrorHelper)?;
tokio::spawn(async move {
if let Err(e) = connection.await {
eprintln!("connection error: {}", e);
}
});
Self::try_from(client).await
}
fn load<'conn, 'query, T>(&'conn mut self, source: T) -> Self::LoadFuture<'conn, 'query>
where
T: AsQuery + Send + 'query,
T::Query: QueryFragment<Self::Backend> + QueryId + Send + 'query,
{
let conn = self.conn.clone();
let stmt_cache = self.stmt_cache.clone();
let metadata_cache = self.metadata_cache.clone();
let tm = self.transaction_state.clone();
let query = source.as_query();
Self::with_prepared_statement(
conn,
stmt_cache,
metadata_cache,
tm,
query,
|conn, stmt, binds| async move {
let res = conn.query_raw(&stmt, binds).await.map_err(ErrorHelper)?;
Ok(res
.map_err(|e| diesel::result::Error::from(ErrorHelper(e)))
.map_ok(PgRow::new)
.boxed())
},
)
.boxed()
}
fn execute_returning_count<'conn, 'query, T>(
&'conn mut self,
source: T,
) -> Self::ExecuteFuture<'conn, 'query>
where
T: QueryFragment<Self::Backend> + QueryId + Send + 'query,
{
Self::with_prepared_statement(
self.conn.clone(),
self.stmt_cache.clone(),
self.metadata_cache.clone(),
self.transaction_state.clone(),
source,
|conn, stmt, binds| async move {
let binds = binds
.iter()
.map(|b| b as &(dyn ToSql + Sync))
.collect::<Vec<_>>();
let res = tokio_postgres::Client::execute(&conn, &stmt, &binds as &[_])
.await
.map_err(ErrorHelper)?;
Ok(res as usize)
},
)
.boxed()
}
fn transaction_state(&mut self) -> &mut AnsiTransactionManager {
// there should be no other pending future when this is called
// that means there is only one instance of this arc and
// we can simply access the inner data
if let Some(tm) = Arc::get_mut(&mut self.transaction_state) {
tm.get_mut()
} else {
panic!("Cannot access shared transaction state")
}
}
}
#[inline(always)]
fn update_transaction_manager_status<T>(
query_result: QueryResult<T>,
transaction_manager: &mut AnsiTransactionManager,
) -> QueryResult<T> {
if let Err(diesel::result::Error::DatabaseError(
diesel::result::DatabaseErrorKind::SerializationFailure,
_,
)) = query_result
{
transaction_manager
.status
.set_top_level_transaction_requires_rollback()
}
query_result
}
#[async_trait::async_trait]
impl PrepareCallback<Statement, PgTypeMetadata> for Arc<tokio_postgres::Client> {
async fn prepare(
self,
sql: &str,
metadata: &[PgTypeMetadata],
_is_for_cache: PrepareForCache,
) -> QueryResult<(Statement, Self)> {
let bind_types = metadata
.iter()
.map(type_from_oid)
.collect::<QueryResult<Vec<_>>>()?;
let stmt = self
.prepare_typed(sql, &bind_types)
.await
.map_err(ErrorHelper);
Ok((stmt?, self))
}
}
fn type_from_oid(t: &PgTypeMetadata) -> QueryResult<Type> {
let oid = t
.oid()
.map_err(|e| diesel::result::Error::SerializationError(Box::new(e) as _))?;
if let Some(tpe) = Type::from_oid(oid) {
return Ok(tpe);
}
Ok(Type::new(
"diesel_custom_type".into(),
oid,
tokio_postgres::types::Kind::Simple,
"public".into(),
))
}
impl AsyncPgConnection {
/// Build a transaction, specifying additional details such as isolation level
///
/// See [`TransactionBuilder`] for more examples.
///
/// [`TransactionBuilder`]: crate::pg::TransactionBuilder
///
/// ```rust
/// # include!("../doctest_setup.rs");
/// # use scoped_futures::ScopedFutureExt;
/// #
/// # #[tokio::main(flavor = "current_thread")]
/// # async fn main() {
/// # run_test().await.unwrap();
/// # }
/// #
/// # async fn run_test() -> QueryResult<()> {
/// # use schema::users::dsl::*;
/// # let conn = &mut connection_no_transaction().await;
/// conn.build_transaction()
/// .read_only()
/// .serializable()
/// .deferrable()
/// .run(|conn| async move { Ok(()) }.scope_boxed())
/// .await
/// # }
/// ```
pub fn build_transaction(&mut self) -> TransactionBuilder<Self> {
TransactionBuilder::new(self)
}
/// Construct a new `AsyncPgConnection` instance from an existing [`tokio_postgres::Client`]
pub async fn try_from(conn: tokio_postgres::Client) -> ConnectionResult<Self> {
let mut conn = Self {
conn: Arc::new(conn),
stmt_cache: Arc::new(Mutex::new(StmtCache::new())),
transaction_state: Arc::new(Mutex::new(AnsiTransactionManager::default())),
metadata_cache: Arc::new(Mutex::new(Some(PgMetadataCache::new()))),
};
conn.set_config_options()
.await
.map_err(ConnectionError::CouldntSetupConfiguration)?;
Ok(conn)
}
async fn set_config_options(&mut self) -> QueryResult<()> {
use crate::run_query_dsl::RunQueryDsl;
diesel::sql_query("SET TIME ZONE 'UTC'")
.execute(self)
.await?;
diesel::sql_query("SET CLIENT_ENCODING TO 'UTF8'")
.execute(self)
.await?;
Ok(())
}
async fn with_prepared_statement<'a, T, F, R>(
raw_connection: Arc<tokio_postgres::Client>,
stmt_cache: Arc<Mutex<StmtCache<diesel::pg::Pg, Statement>>>,
metadata_cache: Arc<Mutex<Option<PgMetadataCache>>>,
tm: Arc<Mutex<AnsiTransactionManager>>,
query: T,
callback: impl FnOnce(Arc<tokio_postgres::Client>, Statement, Vec<ToSqlHelper>) -> F,
) -> QueryResult<R>
where
T: QueryFragment<diesel::pg::Pg> + QueryId + Send,
F: Future<Output = QueryResult<R>>,
{
let mut bind_collector;
{
loop {
// we need a new bind collector per iteration here
bind_collector = RawBytesBindCollector::<diesel::pg::Pg>::new();
let (res, unresolved_types) = {
let mut metadata_cache_lock = metadata_cache.lock().await;
let mut metadata_lookup =
PgAsyncMetadataLookup::new(metadata_cache_lock.take().unwrap_or_default());
let res = query.collect_binds(
&mut bind_collector,
&mut metadata_lookup,
&diesel::pg::Pg,
);
let PgAsyncMetadataLookup {
unresolved_types,
metadata_cache,
} = metadata_lookup;
*metadata_cache_lock = Some(metadata_cache);
(res, unresolved_types)
};
if !unresolved_types.is_empty() {
for (schema, lookup_type_name) in unresolved_types {
// as this is an async call and we don't want to infect the whole diesel serialization
// api with async we just error out in the `PgMetadataLookup` implementation below if we encounter
// a type that is not cached yet
// If that's the case we will do the lookup here and try again as the
// type is now cached.
let type_metadata =
lookup_type(schema.clone(), lookup_type_name.clone(), &raw_connection)
.await?;
let mut metadata_cache_lock = metadata_cache.lock().await;
let metadata_cache =
if let Some(ref mut metadata_cache) = *metadata_cache_lock {
metadata_cache
} else {
*metadata_cache_lock = Some(Default::default());
metadata_cache_lock.as_mut().expect("We set it above")
};
metadata_cache.store_type(
PgMetadataCacheKey::new(
schema.map(Cow::Owned),
Cow::Owned(lookup_type_name),
),
type_metadata,
);
// just try again to get the binds, now that we've inserted the
// type into the lookup list
}
} else {
// bubble up any error as soon as we have done all lookups
res?;
break;
}
}
}
let stmt = {
let mut stmt_cache = stmt_cache.lock().await;
stmt_cache
.cached_prepared_statement(
query,
&bind_collector.metadata,
raw_connection.clone(),
&diesel::pg::Pg,
)
.await?
.0
.clone()
};
let binds = bind_collector
.metadata
.into_iter()
.zip(bind_collector.binds)
.map(|(meta, bind)| ToSqlHelper(meta, bind))
.collect::<Vec<_>>();
let res = callback(raw_connection, stmt.clone(), binds).await;
let mut tm = tm.lock().await;
update_transaction_manager_status(res, &mut tm)
}
}
struct PgAsyncMetadataLookup {
unresolved_types: Vec<(Option<String>, String)>,
metadata_cache: PgMetadataCache,
}
impl PgAsyncMetadataLookup {
fn new(metadata_cache: PgMetadataCache) -> Self {
Self {
unresolved_types: Vec::new(),
metadata_cache,
}
}
}
impl PgMetadataLookup for PgAsyncMetadataLookup {
fn lookup_type(&mut self, type_name: &str, schema: Option<&str>) -> PgTypeMetadata {
let cache_key =
PgMetadataCacheKey::new(schema.map(Cow::Borrowed), Cow::Borrowed(type_name));
if let Some(metadata) = self.metadata_cache.lookup_type(&cache_key) {
metadata
} else {
let cache_key = cache_key.into_owned();
self.unresolved_types
.push((schema.map(ToOwned::to_owned), type_name.to_owned()));
PgTypeMetadata::from_result(Err(FailedToLookupTypeError::new(cache_key)))
}
}
}
async fn lookup_type(
schema: Option<String>,
type_name: String,
raw_connection: &tokio_postgres::Client,
) -> QueryResult<(u32, u32)> {
let r = if let Some(schema) = schema.as_ref() {
raw_connection
.query_one(
"SELECT pg_type.oid, pg_type.typarray FROM pg_type \
INNER JOIN pg_namespace ON pg_type.typnamespace = pg_namespace.oid \
WHERE pg_type.typname = $1 AND pg_namespace.nspname = $2 \
LIMIT 1",
&[&type_name, schema],
)
.await
.map_err(ErrorHelper)?
} else {
raw_connection
.query_one(
"SELECT pg_type.oid, pg_type.typarray FROM pg_type \
WHERE pg_type.oid = quote_ident($1)::regtype::oid \
LIMIT 1",
&[&type_name],
)
.await
.map_err(ErrorHelper)?
};
Ok((r.get(0), r.get(1)))
}
#[cfg(any(feature = "deadpool", feature = "bb8", feature = "mobc"))]
impl crate::pooled_connection::PoolableConnection for AsyncPgConnection {}
#[cfg(test)]
pub mod tests {
use super::*;
use crate::run_query_dsl::RunQueryDsl;
use diesel::sql_types::Integer;
use diesel::IntoSql;
#[tokio::test]
async fn pipelining() {
let database_url =
std::env::var("DATABASE_URL").expect("DATABASE_URL must be set in order to run tests");
let mut conn = crate::AsyncPgConnection::establish(&database_url)
.await
.unwrap();
let q1 = diesel::select(1_i32.into_sql::<Integer>());
let q2 = diesel::select(2_i32.into_sql::<Integer>());
let f1 = q1.get_result::<i32>(&mut conn);
let f2 = q2.get_result::<i32>(&mut conn);
let (r1, r2) = futures::try_join!(f1, f2).unwrap();
assert_eq!(r1, 1);
assert_eq!(r2, 2);
}
}