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Diffstat (limited to 'doc/manual/src/architecture/store/store.md')
| -rw-r--r-- | doc/manual/src/architecture/store/store.md | 23 |
1 files changed, 17 insertions, 6 deletions
diff --git a/doc/manual/src/architecture/store/store.md b/doc/manual/src/architecture/store/store.md index 5a0f4a2df..a3d9e2eeb 100644 --- a/doc/manual/src/architecture/store/store.md +++ b/doc/manual/src/architecture/store/store.md @@ -52,15 +52,26 @@ References are [opaque][opaque-data-type], [unique identifiers][unique-identifie The only way to obtain references is by adding or building store objects. A reference will always point to exactly one store object. -An added store object cannot have references, unless it is a build task. +Nix stores have the *closure property*: for each store object in the store, all the store objects it references must also be in the store. -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. +Adding, building, copying and deleting store objects must be done in a way that obeys this property: -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. +- A newly added store object cannot have references, unless it is a build task. -<!-- more details in section on garbage collection, link to it once it exists --> +- Build results must only refer to store objects in the closure of the build inputs. + + Building a store object will add appropriate references, according to provided build instructions. + These references can only come from declared build inputs. + +- Store objects being copied must refer to objects already in the destination store. + + Recursive copying must either proceed in dependency order or be atomic. + +- We can only safely delete store objects which are not reachable from any reference still in use. + + Garbage collection will delete all store objects that cannot be reached from any reference in use. + + <!-- more details in section on garbage collection, link to it once it exists --> [garbage-collection]: https://en.m.wikipedia.org/wiki/Garbage_collection_(computer_science) [immutable-object]: https://en.m.wikipedia.org/wiki/Immutable_object |