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//! High-level access to database. //! //! # Overview //! //! The core type in this module is the [`Access`] trait, which provides ability to access //! [indexes] from the database. The `Access` trait has several implementations: //! //! - `Access` is implemented for [`RawAccess`]es, that is, types that provide access to the //! entire database. [`Snapshot`], [`Fork`] and [`ReadonlyFork`] fall into this category. //! - [`Prefixed`] restricts an access to a single *namespace*. //! - [`Migration`]s are used for data created during [migrations]. Similar to `Prefixed`, migrations //! are separated by namespaces. //! - [`Scratchpad`]s can be used for temporary data. They are distinguished by namespaces as well. //! //! [`CopyAccessExt`] extends [`Access`] and provides helper methods to instantiate indexes. This //! is useful in quick-and-dirty testing. For more complex applications, consider deriving //! data schema via [`FromAccess`]. //! //! # Guarantees //! //! - Namespaced accesses (`Prefixed`, `Migration`s and `Scratchpad`s) do not intersect (i.e., //! do not have common indexes) for different namespaces. They also do not intersect for //! different access types, even for the same namespace; for example, a `Prefixed` access //! can never access an index from a `Migration` or a `Scratchpad` and vice versa. //! - For all listed `Access` implementations, different addresses *within* an `Access` correspond //! to different indexes. //! - However, if we consider multiple accesses, indexes can alias. For example, an index //! with address `bar` from a `Prefixed<&Fork>` in namespace `foo` can also be accessed via //! address `foo.bar` from the underlying `Fork`. //! //! [`Access`]: trait.Access.html //! [indexes]: ../index.html#indexes //! [`RawAccess`]: trait.RawAccess.html //! [`Snapshot`]: ../trait.Snapshot.html //! [`Fork`]: ../struct.Fork.html //! [`ReadonlyFork`]: ../struct.ReadonlyFork.html //! [`Prefixed`]: struct.Prefixed.html //! [`Migration`]: ../migration/struct.Migration.html //! [migrations]: ../migration/index.html //! [`Scratchpad`]: ../migration/struct.Scratchpad.html //! [`CopyAccessExt`]: trait.CopyAccessExt.html //! [`FromAccess`]: trait.FromAccess.html use thiserror::Error; use std::fmt; pub use self::extensions::{AccessExt, CopyAccessExt}; pub use crate::views::{AsReadonly, RawAccess, RawAccessMut}; use crate::{ validation::assert_valid_name_component, views::{GroupKeys, IndexAddress, IndexMetadata, IndexType, ViewWithMetadata}, BinaryKey, }; mod extensions; /// High-level access to database data. /// /// This trait is not intended to be implemented by the types outside the crate; indeed, /// it instantiates several crate-private types. Correspondingly, `Access` methods /// rarely need to be used directly; use [its extension trait][`CopyAccessExt`] instead. /// /// [`CopyAccessExt`]: trait.CopyAccessExt.html /// /// # Examples /// /// `Access` can be used as a bound on structured database objects and their /// readonly methods: /// /// ``` /// use matterdb::{access::Access, ListIndex, MapIndex}; /// /// struct Schema<T: Access> { /// list: ListIndex<T::Base, u64>, /// map: MapIndex<T::Base, str, u64>, /// } /// /// impl<T: Access> Schema<T> { /// fn get_some_data(&self) -> Option<u64> { /// Some(self.list.get(0)? + self.map.get("foo")?) /// } /// } /// ``` pub trait Access: Clone { /// Raw access serving as the basis for created indexes. type Base: RawAccess; /// Gets index metadata at the specified address, or `None` if there is no index. fn get_index_metadata(self, addr: IndexAddress) -> Result<Option<IndexMetadata>, AccessError>; /// Gets or creates a generic view with the specified address. fn get_or_create_view( self, addr: IndexAddress, index_type: IndexType, ) -> Result<ViewWithMetadata<Self::Base>, AccessError>; /// Returns an iterator over keys in a group with the specified address. /// /// The iterator buffers keys in memory and may become inconsistent for accesses /// based on [`ReadonlyFork`]. /// /// [`ReadonlyFork`]: ../struct.ReadonlyFork.html fn group_keys<K>(self, base_addr: IndexAddress) -> GroupKeys<Self::Base, K> where K: BinaryKey + ?Sized, Self::Base: AsReadonly<Readonly = Self::Base>; } impl<T: RawAccess> Access for T { type Base = Self; fn get_index_metadata(self, addr: IndexAddress) -> Result<Option<IndexMetadata>, AccessError> { ViewWithMetadata::get_metadata(self, &addr) } fn get_or_create_view( self, addr: IndexAddress, index_type: IndexType, ) -> Result<ViewWithMetadata<Self::Base>, AccessError> { ViewWithMetadata::get_or_create(self, &addr, index_type) } fn group_keys<K>(self, base_addr: IndexAddress) -> GroupKeys<Self::Base, K> where K: BinaryKey + ?Sized, Self::Base: AsReadonly<Readonly = Self::Base>, { GroupKeys::new(self, &base_addr) } } /// Access that prepends the specified prefix to each created view. The prefix is separated /// from user-provided names with a dot char `'.'`. /// /// Since the prefix itself cannot contain a dot, `Prefixed` accesses provide namespace /// separation. A set of indexes to which `Prefixed` provides access does not intersect /// with a set of indexes accessed by a `Prefixed` instance with another prefix. Additionally, /// index in `Prefixed` accesses do not intersect with indexes in special-purpose `Access` /// implementations ([`Migration`]s and [`Scratchpad`]s). /// /// [`Migration`]: ../migration/struct.Migration.html /// [`Scratchpad`]: ../migration/struct.Scratchpad.html /// /// # Examples /// /// ``` /// use matterdb::{access::{AccessExt, CopyAccessExt, Prefixed}, Database, TemporaryDB}; /// /// let db = TemporaryDB::new(); /// let fork = db.fork(); /// let prefixed = Prefixed::new("prefixed", &fork); /// prefixed.get_list("list").extend(vec![1_u32, 2, 3]); /// let same_list = fork.get_list::<_, u32>("prefixed.list"); /// assert_eq!(same_list.len(), 3); /// ``` #[derive(Debug, Clone)] pub struct Prefixed<T> { access: T, prefix: String, } // **NB.** Must not be made public! This would allow the caller to violate access restrictions // imposed by `Prefixed`. impl<T> Prefixed<T> { pub(crate) fn access(&self) -> &T { &self.access } pub(crate) fn into_parts(self) -> (String, T) { (self.prefix, self.access) } } impl<T: RawAccess> Prefixed<T> { /// Creates a new prefixed access. /// /// # Panics /// /// - Will panic if the prefix is not a [valid prefix name]. /// /// [valid prefix name]: ../validation/fn.is_valid_index_name_component.html pub fn new(prefix: impl Into<String>, access: T) -> Self { let prefix = prefix.into(); assert_valid_name_component(prefix.as_ref()); Self { access, prefix } } } impl<T: RawAccess> Access for Prefixed<T> { type Base = T; fn get_index_metadata(self, addr: IndexAddress) -> Result<Option<IndexMetadata>, AccessError> { let prefixed_addr = addr.prepend_name(self.prefix.as_ref()); self.access.get_index_metadata(prefixed_addr) } fn get_or_create_view( self, addr: IndexAddress, index_type: IndexType, ) -> Result<ViewWithMetadata<Self::Base>, AccessError> { let prefixed_addr = addr.prepend_name(self.prefix.as_ref()); self.access.get_or_create_view(prefixed_addr, index_type) } fn group_keys<K>(self, base_addr: IndexAddress) -> GroupKeys<Self::Base, K> where K: BinaryKey + ?Sized, Self::Base: AsReadonly<Readonly = Self::Base>, { let prefixed_addr = base_addr.prepend_name(self.prefix.as_ref()); self.access.group_keys(prefixed_addr) } } /// Access error together with the location information. #[derive(Debug, Error)] pub struct AccessError { /// Address of the index where the error has occurred. pub addr: IndexAddress, /// Error kind. #[source] pub kind: AccessErrorKind, } impl fmt::Display for AccessError { fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result { // TODO: implement `Display` for `IndexAddress` for human-readable errors write!(formatter, "Error accessing {:?}: {}", self.addr, self.kind) } } /// Error that can be emitted during accessing an object from the database. #[derive(Debug, Error)] #[non_exhaustive] pub enum AccessErrorKind { /// Index has wrong type. #[error("Wrong index type: expected {:?}, but got {:?}", expected, actual)] WrongIndexType { /// Expected index type. expected: IndexType, /// Actual index type. actual: IndexType, }, /// Index name is reserved. It's forbidden for user to create indexes with names /// starting with `__` and not containing a dot `.`. #[error("Index name is reserved")] ReservedName, /// Index name is empty. #[error("Index name must not be empty")] EmptyName, /// Index contains invalid characters. #[error("Invalid characters used in name ({}). Use {}", name, allowed_chars)] InvalidCharsInName { /// Name that contains invalid chars. name: String, /// Characters allowed in name. allowed_chars: &'static str, }, /// Invalid tombstone location. #[error("Invalid tombstone location. Tombstones can only be created in migrations")] InvalidTombstone, /// Custom error. #[error("{0}")] Custom(#[source] anyhow::Error), } /// Constructs an object atop the database. The constructed object provides access to data /// in the DB, akin to an object-relational mapping. /// /// The access to DB can be readonly or read-write, depending on the `T: Access` type param. /// Most object should implement `FromAccess<T>` for all `T: Access`. /// /// Simplest `FromAccess` implementors are indexes; it is also implemented for [`Lazy`] and [`Group`]. /// `FromAccess` can be implemented for more complex *components*. Thus, `FromAccess` can /// be used to compose storage objects from simpler ones. /// /// [`Lazy`]: ../struct.Lazy.html /// [`Group`]: ../indexes/group/struct.Group.html /// /// # Examples /// /// Component with two inner indexes. `FromAccess` is automatically derived using /// the `matterdb_derive` crate. /// /// ``` /// use matterdb_derive::FromAccess; /// # use matterdb::{ /// # access::{Access, CopyAccessExt, AccessError, FromAccess, RawAccessMut}, /// # Database, Entry, Group, Lazy, MapIndex, IndexAddress, TemporaryDB, /// # }; /// /// #[derive(FromAccess)] /// struct InsertOnlyMap<T: Access> { /// map: MapIndex<T::Base, str, String>, /// len: Entry<T::Base, u64>, /// } /// /// impl<T: Access> InsertOnlyMap<T> /// where /// T::Base: RawAccessMut, /// { /// fn insert(&mut self, key: &str, value: String) -> bool { /// if self.map.contains(key) { return false; } /// self.map.put(&key.to_owned(), value); /// self.len.set(self.len.get().unwrap_or_default() + 1); /// true /// } /// } /// /// # fn main() -> Result<(), AccessError> { /// let db = TemporaryDB::new(); /// let fork = db.fork(); /// # { /// let mut map = InsertOnlyMap::from_access(&fork, "test".into())?; /// map.insert("foo", "FOO".to_owned()); /// map.insert("bar", "BAR".to_owned()); /// assert_eq!(map.len.get(), Some(2)); /// # } /// /// // Components could be used with `Group` / `Lazy` out of the box: /// let lazy_map: Lazy<_, InsertOnlyMap<_>> = /// Lazy::from_access(&fork, "test".into())?; /// assert_eq!(lazy_map.get().map.get("foo").unwrap(), "FOO"); /// /// let group_of_maps: Group<_, u16, InsertOnlyMap<_>> = /// fork.get_group("test_group"); /// group_of_maps.get(&1).insert("baz", "BAZ".to_owned()); /// group_of_maps.get(&2).insert("baz", "BUZZ".to_owned()); /// # assert_eq!(group_of_maps.get(&1).len.get(), Some(1)); /// # assert_eq!( /// # fork.get_map::<_, str, String>(("test_group.map", &2_u16)).get("baz").unwrap(), /// # "BUZZ" /// # ); /// # Ok(()) /// # } /// ``` pub trait FromAccess<T: Access>: Sized { /// Constructs the object at the given address. /// /// # Return value /// /// Returns the constructed object. An error should be returned if the object cannot be /// constructed. fn from_access(access: T, addr: IndexAddress) -> Result<Self, AccessError>; /// Constructs the object from the root of the `access`. /// /// The default implementation uses `Self::from_access()` with an empty address. fn from_root(access: T) -> Result<Self, AccessError> { Self::from_access(access, IndexAddress::default()) } } #[cfg(test)] mod tests { use super::{Access, AccessExt, CopyAccessExt, FromAccess, IndexType, Prefixed}; use crate::{Database, ListIndex, TemporaryDB}; #[test] fn prefixed_works() { let db = TemporaryDB::new(); let fork = db.fork(); { let prefixed = Prefixed::new("test", &fork); let mut list = prefixed.get_list::<_, i32>("foo"); list.extend(vec![1, 2, 3]); } { let list = fork.get_list::<_, i32>("test.foo"); assert_eq!(list.len(), 3); assert_eq!(list.iter().collect::<Vec<_>>(), vec![1, 2, 3]); } db.merge_sync(fork.into_patch()).unwrap(); let snapshot = db.snapshot(); let list = snapshot.get_list::<_, i32>("test.foo"); assert_eq!(list.len(), 3); assert_eq!(list.iter().collect::<Vec<_>>(), vec![1, 2, 3]); let prefixed = Prefixed::new("test", &snapshot); let list = prefixed.get_list::<_, i32>("foo"); assert_eq!(list.len(), 3); assert_eq!(list.iter().collect::<Vec<_>>(), vec![1, 2, 3]); } #[test] fn prefixed_views_do_not_collide() { let db = TemporaryDB::new(); let fork = db.fork(); let foo_space = Prefixed::new("foo", &fork); let bar_space = Prefixed::new("bar", &fork); { let mut list = foo_space.get_list("test"); list.push("Test".to_owned()); let mut other_list = bar_space.get_list("test"); other_list.extend(vec![1_u64, 2, 3]); assert_eq!(list.len(), 1); assert_eq!(other_list.len(), 3); } db.merge_sync(fork.into_patch()).unwrap(); let snapshot = db.snapshot(); let foo_space = Prefixed::new("foo", &snapshot); let list = foo_space.get_list::<_, String>("test"); assert_eq!(list.get(0), Some("Test".to_owned())); let bar_space = Prefixed::new("bar", &snapshot); let list = bar_space.get_list::<_, u64>("test"); assert_eq!(list.get(0), Some(1_u64)); // It is possible to create indexes of the different types at the same (relative) address // in the different `Prefixed` instances. let fork = db.fork(); let foo_space = Prefixed::new("foo", &fork); foo_space.get_list::<_, u32>(("fam", &1_u32)); let bar_space = Prefixed::new("bar", &fork); bar_space.get_map::<_, u32, u32>(("fam", &1_u32)); db.merge_sync(fork.into_patch()).unwrap(); let snapshot = db.snapshot(); let view = snapshot .as_ref() .get_or_create_view(("foo.fam", &1_u32).into(), IndexType::List) .unwrap(); assert!(!view.is_phantom()); let view = snapshot .as_ref() .get_or_create_view(("bar.fam", &1_u32).into(), IndexType::Map) .unwrap(); assert!(!view.is_phantom()); } #[test] fn from_root_method() { let db = TemporaryDB::new(); let fork = db.fork(); let prefixed = Prefixed::new("foo", &fork); { let mut list: ListIndex<_, u64> = ListIndex::from_root(prefixed).unwrap(); list.extend(vec![1, 2, 3]); } assert_eq!(fork.get_list::<_, u64>("foo").len(), 3); } }