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Iterate on Database trait comments

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Eric Eastwood
2026-06-24 16:09:29 -05:00
parent 7ed525ddd1
commit 8ddab4f23e
1 changed files with 13 additions and 18 deletions
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rust/src/storage/db/mod.rs
+13 -18
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@@ -25,28 +25,25 @@ pub mod rust_db_pool;
/// A type-erased `run_interaction` callback.
///
/// This is the dyn-compatible form of the `func` passed to
/// [`DatabasePoolExt::run_interaction`]: the concrete result type `R` is boxed up
/// as `Box<dyn Any + Send>` (see [`ErasedResult`]) so [`DatabasePool`] can stay
/// dyn-compatible (and usable as `Box<dyn DatabasePool>`). The ergonomic
/// [`DatabasePoolExt::run_interaction`] handles the boxing and downcasts the
/// result back to `R` for the caller.
/// [`DatabasePoolExt::run_interaction`].
///
/// The ergonomic [`DatabasePoolExt::run_interaction`] handles the boxing and downcasts
/// the result back to `R` for the caller.
///
/// It may be invoked multiple times under certain failure modes (serialization
/// and deadlock errors), so it is `Fn` rather than `FnOnce`.
pub type ErasedInteraction =
Box<dyn for<'txn> Fn(&'txn mut dyn Transaction) -> BoxFuture<'txn, ErasedResult> + Send>;
/// The type-erased result of an [`ErasedInteraction`]: the concrete `R` boxed up
/// as `Box<dyn Any + Send>` so it can pass back through the dyn-compatible
/// The type-erased *result* of an [`ErasedInteraction`]
/// [`DatabasePool::run_interaction_erased`].
pub type ErasedResult = anyhow::Result<Box<dyn Any + Send>>;
/// A database connection pool.
///
/// Held behind a trait object (e.g. `Box<dyn DatabasePool>`) so a single `Store`
/// can run against either the Python-backed pool (in Synapse, see
/// [`python_db_pool`]) or a native `tokio-postgres` pool (in `synapse-rust-apps`,
/// see [`rust_db_pool`]).
/// Held behind a trait object (e.g. `Box<dyn DatabasePool>`) as it can be backed by
/// either the Python-backed pool (in Synapse, see [`python_db_pool`]) or a Rust native
/// `tokio-postgres` pool (expected to be used in `synapse-rust-apps`).
///
/// To keep the trait dyn-compatible, we have to specify a type-erased
/// [`run_interaction_erased`](Self::run_interaction_erased) version; callers should
@@ -69,9 +66,6 @@ pub trait DatabasePool: Send + Sync {
}
/// Ergonomic, strongly-typed access to a [`DatabasePool`].
///
/// Blanket-implemented for every `T: DatabasePool + ?Sized`, so it is available
/// both on concrete pools and on `dyn DatabasePool` trait objects.
pub trait DatabasePoolExt: DatabasePool {
/// Starts a transaction on the database and runs the given function,
/// returning its result.
@@ -139,12 +133,13 @@ pub trait DatabasePoolExt: DatabasePool {
}
}
// Make [`run_interaction`](DatabasePoolExt::run_interaction) available on all
// `DatabasePool`
/// Blanket-implemented for every [`DatabasePool`] so
/// [`run_interaction`](DatabasePoolExt::run_interaction) is always available
impl<T: DatabasePool + ?Sized> DatabasePoolExt for T {}
/// A [`tokio_postgres::Transaction`] looking thing that we can use on the Rust side to
/// interact with the database
/// A transaction to interact with the database
///
/// Based on the ergonomics of [`tokio_postgres::Transaction`]
#[async_trait::async_trait]
pub trait Transaction: Send {
// `async` as this is representing a round-trip between the app and database