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| -rw-r--r-- | doc/manual/src/architecture/store/store.md | 57 |
1 files changed, 32 insertions, 25 deletions
diff --git a/doc/manual/src/architecture/store/store.md b/doc/manual/src/architecture/store/store.md index 1640944ad..5a0f4a2df 100644 --- a/doc/manual/src/architecture/store/store.md +++ b/doc/manual/src/architecture/store/store.md @@ -2,33 +2,49 @@ A Nix store is a collection of *store objects*. -A store object can hold arbitrary *data* and *references* to other store objects. -Nix makes no distinction if store objects are used as build inputs, build results, or build tasks. +A store object can hold -```haskell -data Store = Set StoreObject +- arbitrary *data* +- *references* to other store objects. -data StoreObject = StoreObject { - data :: Data -, references :: Set Reference -} -``` +Nix makes no distinction if store objects are build inputs, build results, or build tasks. A Nix store can *add*, *retrieve*, and *delete* store objects. + [ data ] + | + V + [ store ] ---> add ----> [ store' ] [ reference ] + +<!-- --> + + [ reference ] + | + V + [ store ] ---> get ----> [ store object ] + +<!-- --> + + [ reference ] + | + V + [ store ] --> delete --> [ store' ] + + It can *perform builds*, that is, create new store objects by transforming build inputs into build outputs, using instructions from the build tasks. + + [ reference ] + | + V + [ store ] --> build --(maybe)--> [ store' ] [ reference' ] + + As it keeps track of references, it can [garbage-collect][garbage-collection] unused store objects. -```haskell -add :: Store -> Data -> (Store, Reference) -get :: Store -> Reference -> StoreObject -delete :: Store -> Reference -> Store -build :: Store -> Reference -> Maybe (Store, Reference) + [ store ] --> collect garbage --> [ store' ] -collectGarbage :: Store -> Store -``` Store objects are [immutable][immutable-object]: once created, they do not change until they are deleted. @@ -41,15 +57,6 @@ An added store object cannot have references, unless it is a build task. Building a store object will add appropriate references, according to provided build instructions. These references can only come from declared build inputs, and are not known to build instructions a priori. -```haskell -data Data = Data | Task BuildTask - -data BuildTask = BuildTask { - instructions :: Reference -, inputs :: [Reference] -} -``` - A store object cannot be deleted as long as it is reachable from a reference still in use. Garbage collection will delete all store objects that cannot be reached from any reference in use. |