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#![warn(rust_2018_idioms)] #![warn(missing_docs)] //! The salsa crate is a crate for incremental recomputation. It //! permits you to define a "database" of queries with both inputs and //! values derived from those inputs; as you set the inputs, you can //! re-execute the derived queries and it will try to re-use results //! from previous invocations as appropriate. mod blocking_future; mod derived; mod doctest; mod durability; mod input; mod intern_id; mod interned; mod lru; mod revision; mod runtime; mod storage; pub mod debug; /// Items in this module are public for implementation reasons, /// and are exempt from the SemVer guarantees. #[doc(hidden)] pub mod plumbing; use crate::plumbing::DerivedQueryStorageOps; use crate::plumbing::InputQueryStorageOps; use crate::plumbing::LruQueryStorageOps; use crate::plumbing::QueryStorageMassOps; use crate::plumbing::QueryStorageOps; pub use crate::revision::Revision; use std::fmt::{self, Debug}; use std::hash::Hash; use std::sync::Arc; pub use crate::durability::Durability; pub use crate::intern_id::InternId; pub use crate::interned::InternKey; pub use crate::runtime::Runtime; pub use crate::runtime::RuntimeId; pub use crate::storage::Storage; /// The base trait which your "query context" must implement. Gives /// access to the salsa runtime, which you must embed into your query /// context (along with whatever other state you may require). pub trait Database: plumbing::DatabaseOps { /// Iterates through all query storage and removes any values that /// have not been used since the last revision was created. The /// intended use-cycle is that you first execute all of your /// "main" queries; this will ensure that all query values they /// consume are marked as used. You then invoke this method to /// remove other values that were not needed for your main query /// results. fn sweep_all(&self, strategy: SweepStrategy) { // Note that we do not acquire the query lock (or any locks) // here. Each table is capable of sweeping itself atomically // and there is no need to bring things to a halt. That said, // users may wish to guarantee atomicity. let runtime = self.salsa_runtime(); self.for_each_query(&mut |query_storage| query_storage.sweep(runtime, strategy)); } /// This function is invoked at key points in the salsa /// runtime. It permits the database to be customized and to /// inject logging or other custom behavior. fn salsa_event(&self, event_fn: Event) { #![allow(unused_variables)] } /// This function is invoked when a dependent query is being computed by the /// other thread, and that thread panics. fn on_propagated_panic(&self) -> ! { panic!("concurrent salsa query panicked") } /// Gives access to the underlying salsa runtime. fn salsa_runtime(&self) -> &Runtime { self.ops_salsa_runtime() } /// Gives access to the underlying salsa runtime. fn salsa_runtime_mut(&mut self) -> &mut Runtime { self.ops_salsa_runtime_mut() } } /// The `Event` struct identifies various notable things that can /// occur during salsa execution. Instances of this struct are given /// to `salsa_event`. pub struct Event { /// The id of the snapshot that triggered the event. Usually /// 1-to-1 with a thread, as well. pub runtime_id: RuntimeId, /// What sort of event was it. pub kind: EventKind, } impl fmt::Debug for Event { fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { fmt.debug_struct("Event") .field("runtime_id", &self.runtime_id) .field("kind", &self.kind) .finish() } } /// An enum identifying the various kinds of events that can occur. pub enum EventKind { /// Occurs when we found that all inputs to a memoized value are /// up-to-date and hence the value can be re-used without /// executing the closure. /// /// Executes before the "re-used" value is returned. DidValidateMemoizedValue { /// The database-key for the affected value. Implements `Debug`. database_key: DatabaseKeyIndex, }, /// Indicates that another thread (with id `other_runtime_id`) is processing the /// given query (`database_key`), so we will block until they /// finish. /// /// Executes after we have registered with the other thread but /// before they have answered us. /// /// (NB: you can find the `id` of the current thread via the /// `salsa_runtime`) WillBlockOn { /// The id of the runtime we will block on. other_runtime_id: RuntimeId, /// The database-key for the affected value. Implements `Debug`. database_key: DatabaseKeyIndex, }, /// Indicates that the function for this query will be executed. /// This is either because it has never executed before or because /// its inputs may be out of date. WillExecute { /// The database-key for the affected value. Implements `Debug`. database_key: DatabaseKeyIndex, }, } impl fmt::Debug for EventKind { fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { match self { EventKind::DidValidateMemoizedValue { database_key } => fmt .debug_struct("DidValidateMemoizedValue") .field("database_key", database_key) .finish(), EventKind::WillBlockOn { other_runtime_id, database_key, } => fmt .debug_struct("WillBlockOn") .field("other_runtime_id", other_runtime_id) .field("database_key", database_key) .finish(), EventKind::WillExecute { database_key } => fmt .debug_struct("WillExecute") .field("database_key", database_key) .finish(), } } } #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)] enum DiscardIf { Never, Outdated, Always, } impl Default for DiscardIf { fn default() -> DiscardIf { DiscardIf::Never } } #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)] enum DiscardWhat { Nothing, Values, Everything, } impl Default for DiscardWhat { fn default() -> DiscardWhat { DiscardWhat::Nothing } } /// The sweep strategy controls what data we will keep/discard when we /// do a GC-sweep. The default (`SweepStrategy::default`) is a no-op, /// use `SweepStrategy::discard_outdated` constructor or `discard_*` /// and `sweep_*` builder functions to construct useful strategies. #[derive(Debug, Copy, Clone, Default, PartialEq, Eq)] pub struct SweepStrategy { discard_if: DiscardIf, discard_what: DiscardWhat, shrink_to_fit: bool, } impl SweepStrategy { /// Convenience function that discards all data not used thus far in the /// current revision. /// /// Equivalent to `SweepStrategy::default().discard_everything()`. pub fn discard_outdated() -> SweepStrategy { SweepStrategy::default() .discard_everything() .sweep_outdated() } /// Collects query values. /// /// Query dependencies are left in the database, which allows to quickly /// determine if the query is up to date, and avoid recomputing /// dependencies. pub fn discard_values(self) -> SweepStrategy { SweepStrategy { discard_what: self.discard_what.max(DiscardWhat::Values), ..self } } /// Collects both values and information about dependencies. /// /// Dependant queries will be recomputed even if all inputs to this query /// stay the same. pub fn discard_everything(self) -> SweepStrategy { SweepStrategy { discard_what: self.discard_what.max(DiscardWhat::Everything), ..self } } /// Process all keys, not verefied at the current revision. pub fn sweep_outdated(self) -> SweepStrategy { SweepStrategy { discard_if: self.discard_if.max(DiscardIf::Outdated), ..self } } /// Process all keys. pub fn sweep_all_revisions(self) -> SweepStrategy { SweepStrategy { discard_if: self.discard_if.max(DiscardIf::Always), ..self } } } /// Indicates a database that also supports parallel query /// evaluation. All of Salsa's base query support is capable of /// parallel execution, but for it to work, your query key/value types /// must also be `Send`, as must any additional data in your database. pub trait ParallelDatabase: Database + Send { /// Creates a second handle to the database that holds the /// database fixed at a particular revision. So long as this /// "frozen" handle exists, any attempt to [`set`] an input will /// block. /// /// [`set`]: struct.QueryTable.html#method.set /// /// This is the method you are meant to use most of the time in a /// parallel setting where modifications may arise asynchronously /// (e.g., a language server). In this context, it is common to /// wish to "fork off" a snapshot of the database performing some /// series of queries in parallel and arranging the results. Using /// this method for that purpose ensures that those queries will /// see a consistent view of the database (it is also advisable /// for those queries to use the [`is_current_revision_canceled`] /// method to check for cancellation). /// /// [`is_current_revision_canceled`]: struct.Runtime.html#method.is_current_revision_canceled /// /// # Panics /// /// It is not permitted to create a snapshot from inside of a /// query. Attepting to do so will panic. /// /// # Deadlock warning /// /// The intended pattern for snapshots is that, once created, they /// are sent to another thread and used from there. As such, the /// `snapshot` acquires a "read lock" on the database -- /// therefore, so long as the `snapshot` is not dropped, any /// attempt to `set` a value in the database will block. If the /// `snapshot` is owned by the same thread that is attempting to /// `set`, this will cause a problem. /// /// # How to implement this /// /// Typically, this method will create a second copy of your /// database type (`MyDatabaseType`, in the example below), /// cloning over each of the fields from `self` into this new /// copy. For the field that stores the salsa runtime, you should /// use [the `Runtime::snapshot` method][rfm] to create a snapshot of the /// runtime. Finally, package up the result using `Snapshot::new`, /// which is a simple wrapper type that only gives `&self` access /// to the database within (thus preventing the use of methods /// that may mutate the inputs): /// /// [rfm]: struct.Runtime.html#method.snapshot /// /// ```rust,ignore /// impl ParallelDatabase for MyDatabaseType { /// fn snapshot(&self) -> Snapshot<Self> { /// Snapshot::new( /// MyDatabaseType { /// runtime: self.runtime.snapshot(self), /// other_field: self.other_field.clone(), /// } /// ) /// } /// } /// ``` fn snapshot(&self) -> Snapshot<Self>; } /// Simple wrapper struct that takes ownership of a database `DB` and /// only gives `&self` access to it. See [the `snapshot` method][fm] /// for more details. /// /// [fm]: trait.ParallelDatabase.html#method.snapshot #[derive(Debug)] pub struct Snapshot<DB: ?Sized> where DB: ParallelDatabase, { db: DB, } impl<DB> Snapshot<DB> where DB: ParallelDatabase, { /// Creates a `Snapshot` that wraps the given database handle /// `db`. From this point forward, only shared references to `db` /// will be possible. pub fn new(db: DB) -> Self { Snapshot { db } } } impl<DB> std::ops::Deref for Snapshot<DB> where DB: ParallelDatabase, { type Target = DB; fn deref(&self) -> &DB { &self.db } } /// An integer that uniquely identifies a particular query instance within the /// database. Used to track dependencies between queries. Fully ordered and /// equatable but those orderings are arbitrary, and meant to be used only for /// inserting into maps and the like. #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)] pub struct DatabaseKeyIndex { group_index: u16, query_index: u16, key_index: u32, } impl DatabaseKeyIndex { /// Returns the index of the query group containing this key. #[inline] pub fn group_index(self) -> u16 { self.group_index } /// Returns the index of the query within its query group. #[inline] pub fn query_index(self) -> u16 { self.query_index } /// Returns the index of this particular query key within the query. #[inline] pub fn key_index(self) -> u32 { self.key_index } /// Returns a type that gives a user-readable debug output. /// Use like `println!("{:?}", index.debug(db))`. pub fn debug<D: ?Sized>(self, db: &D) -> impl std::fmt::Debug + '_ where D: plumbing::DatabaseOps, { DatabaseKeyIndexDebug { index: self, db } } } /// Helper type for `DatabaseKeyIndex::debug` struct DatabaseKeyIndexDebug<'me, D: ?Sized> where D: plumbing::DatabaseOps, { index: DatabaseKeyIndex, db: &'me D, } impl<D: ?Sized> std::fmt::Debug for DatabaseKeyIndexDebug<'_, D> where D: plumbing::DatabaseOps, { fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { self.db.fmt_index(self.index, fmt) } } /// Trait implements by all of the "special types" associated with /// each of your queries. /// /// Base trait of `Query` that has a lifetime parameter to allow the `DynDb` to be non-'static. pub trait QueryDb<'d>: Sized { /// Dyn version of the associated trait for this query group. type DynDb: ?Sized + Database + HasQueryGroup<Self::Group> + 'd; /// Associate query group struct. type Group: plumbing::QueryGroup<GroupStorage = Self::GroupStorage>; /// Generated struct that contains storage for all queries in a group. type GroupStorage; } /// Trait implements by all of the "special types" associated with /// each of your queries. pub trait Query: Debug + Default + Sized + for<'d> QueryDb<'d> { /// Type that you you give as a parameter -- for queries with zero /// or more than one input, this will be a tuple. type Key: Clone + Debug + Hash + Eq; /// What value does the query return? type Value: Clone + Debug; /// Internal struct storing the values for the query. // type Storage: plumbing::QueryStorageOps<Self>; type Storage; /// A unique index identifying this query within the group. const QUERY_INDEX: u16; /// Name of the query method (e.g., `foo`) const QUERY_NAME: &'static str; /// Extact storage for this query from the storage for its group. fn query_storage<'a>( group_storage: &'a <Self as QueryDb<'_>>::GroupStorage, ) -> &'a Arc<Self::Storage>; } /// Return value from [the `query` method] on `Database`. /// Gives access to various less common operations on queries. /// /// [the `query` method]: trait.Database.html#method.query pub struct QueryTable<'me, Q> where Q: Query, { db: &'me <Q as QueryDb<'me>>::DynDb, storage: &'me Q::Storage, } impl<'me, Q> QueryTable<'me, Q> where Q: Query, Q::Storage: QueryStorageOps<Q>, { /// Constructs a new `QueryTable`. pub fn new(db: &'me <Q as QueryDb<'me>>::DynDb, storage: &'me Q::Storage) -> Self { Self { db, storage } } /// Execute the query on a given input. Usually it's easier to /// invoke the trait method directly. Note that for variadic /// queries (those with no inputs, or those with more than one /// input) the key will be a tuple. pub fn get(&self, key: Q::Key) -> Q::Value { self.try_get(key).unwrap_or_else(|err| panic!("{}", err)) } fn try_get(&self, key: Q::Key) -> Result<Q::Value, CycleError<DatabaseKeyIndex>> { self.storage.try_fetch(self.db, &key) } /// Remove all values for this query that have not been used in /// the most recent revision. pub fn sweep(&self, strategy: SweepStrategy) where Q::Storage: plumbing::QueryStorageMassOps, { self.storage.sweep(self.db.salsa_runtime(), strategy); } /// Completely clears the storage for this query. /// /// This method breaks internal invariants of salsa, so any further queries /// might return nonsense results. It is useful only in very specific /// circumstances -- for example, when one wants to observe which values /// dropped together with the table pub fn purge(&self) where Q::Storage: plumbing::QueryStorageMassOps, { self.storage.purge(); }} /// Return value from [the `query_mut` method] on `Database`. /// Gives access to the `set` method, notably, that is used to /// set the value of an input query. /// /// [the `query_mut` method]: trait.Database.html#method.query_mut pub struct QueryTableMut<'me, Q> where Q: Query + 'me, { db: &'me mut <Q as QueryDb<'me>>::DynDb, storage: Arc<Q::Storage>, } impl<'me, Q> QueryTableMut<'me, Q> where Q: Query, { /// Constructs a new `QueryTableMut`. pub fn new(db: &'me mut <Q as QueryDb<'me>>::DynDb, storage: Arc<Q::Storage>) -> Self { Self { db, storage } } /// Assign a value to an "input query". Must be used outside of /// an active query computation. /// /// If you are using `snapshot`, see the notes on blocking /// and cancellation on [the `query_mut` method]. /// /// [the `query_mut` method]: trait.Database.html#method.query_mut pub fn set(&mut self, key: Q::Key, value: Q::Value) where Q::Storage: plumbing::InputQueryStorageOps<Q>, { self.set_with_durability(key, value, Durability::LOW); } /// Assign a value to an "input query", with the additional /// promise that this value will **never change**. Must be used /// outside of an active query computation. /// /// If you are using `snapshot`, see the notes on blocking /// and cancellation on [the `query_mut` method]. /// /// [the `query_mut` method]: trait.Database.html#method.query_mut pub fn set_with_durability(&mut self, key: Q::Key, value: Q::Value, durability: Durability) where Q::Storage: plumbing::InputQueryStorageOps<Q>, { self.storage.set(self.db, &key, value, durability); } /// Sets the size of LRU cache of values for this query table. /// /// That is, at most `cap` values will be preset in the table at the same /// time. This helps with keeping maximum memory usage under control, at the /// cost of potential extra recalculations of evicted values. /// /// If `cap` is zero, all values are preserved, this is the default. pub fn set_lru_capacity(&self, cap: usize) where Q::Storage: plumbing::LruQueryStorageOps, { self.storage.set_lru_capacity(cap); } /// Marks the computed value as outdated. /// /// This causes salsa to re-execute the query function on the next access to /// the query, even if all dependencies are up to date. /// /// This is most commonly used as part of the [on-demand input /// pattern](https://salsa-rs.github.io/salsa/common_patterns/on_demand_inputs.html). pub fn invalidate(&mut self, key: &Q::Key) where Q::Storage: plumbing::DerivedQueryStorageOps<Q>, { self.storage.invalidate(self.db, key) } } /// The error returned when a query could not be resolved due to a cycle #[derive(Eq, PartialEq, Clone, Debug)] pub struct CycleError<K> { /// The queries that were part of the cycle cycle: Vec<K>, changed_at: Revision, durability: Durability, } impl<K> fmt::Display for CycleError<K> where K: fmt::Debug, { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { writeln!(f, "Internal error, cycle detected:\n")?; for i in &self.cycle { writeln!(f, "{:?}", i)?; } Ok(()) } } // Re-export the procedural macros. #[allow(unused_imports)] #[macro_use] extern crate salsa_macros; use plumbing::HasQueryGroup; #[doc(hidden)] pub use salsa_macros::*;