Trait Db 

pub trait Db {
    // Required methods
    fn query<Q: Query>(&self, query: Q) -> Result<Arc<Q::Output>, QueryError>;
    fn asset<K: AssetKey>(&self, key: K) -> Result<Arc<K::Asset>, QueryError>;
    fn asset_state<K: AssetKey>(
        &self,
        key: K,
    ) -> Result<AssetLoadingState<K>, QueryError>;
    fn list_queries<Q: Query>(&self) -> Vec<Q>;
    fn list_asset_keys<K: AssetKey>(&self) -> Vec<K>;
}

Database trait that provides query execution and asset access.

This trait is implemented by both QueryRuntime and QueryContext, allowing queries to work with either.

• QueryRuntime::query() / QueryRuntime::asset(): No dependency tracking
• QueryContext::query() / QueryContext::asset(): With dependency tracking

Required Methods

fn query<Q: Query>(&self, query: Q) -> Result<Arc<Q::Output>, QueryError>

Execute a query, returning the cached result if available.

fn asset<K: AssetKey>(&self, key: K) -> Result<Arc<K::Asset>, QueryError>

Access an asset by key.

Returns the asset value if ready, or Err(QueryError::Suspend) if still loading. Use this with the ? operator for automatic suspension on loading.

Example

fn query(&self, db: &impl Db) -> Result<MyOutput, QueryError> {
    let data = db.asset(key)?;  // Suspends if loading
    Ok(process(&data))
}

fn asset_state<K: AssetKey>( &self, key: K, ) -> Result<AssetLoadingState<K>, QueryError>

Access an asset’s loading state by key.

Unlike asset(), this method returns the full loading state, allowing you to check if an asset is loading without triggering suspension.

Example

let state = db.asset_state(key)?;
if state.is_loading() {
    // Handle loading case explicitly
} else {
    let value = state.get().unwrap();
}

fn list_queries<Q: Query>(&self) -> Vec<Q>

List all executed queries of a specific type.

fn list_asset_keys<K: AssetKey>(&self) -> Vec<K>

List all resolved asset keys of a specific type.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors

impl<'a, T: Tracer> Db for QueryContext<'a, T>

impl<T: Tracer> Db for QueryRuntime<T>