Trait GraphStore 

pub trait GraphStore {
    // Required methods
    fn relate(
        &self,
        from: u64,
        to: u64,
        relation: &str,
    ) -> Result<u64, MemoryError>;
    fn relations(&self, id: u64) -> Result<Vec<MemoryEdge>, MemoryError>;
    fn incoming_relations(
        &self,
        id: u64,
    ) -> Result<Vec<MemoryEdge>, MemoryError>;
    fn relations_bounded(
        &self,
        id: u64,
        cap: usize,
    ) -> Result<BoundedMemoryEdges, MemoryError>;
    fn incoming_relations_bounded(
        &self,
        id: u64,
        cap: usize,
    ) -> Result<BoundedMemoryEdges, MemoryError>;
    fn unrelate(&self, edge_id: u64) -> Result<bool, MemoryError>;

    // Provided methods
    fn unrelate_from(
        &self,
        from: u64,
        edge_id: u64,
    ) -> Result<bool, MemoryError> { ... }
    fn edge_count(&self) -> Option<usize> { ... }
}

Typed graph edges between facts — the facet behind relate/why and the hub walks. A backend without a graph simply does not implement it, and the service methods that need it stop existing for that backend at compile time.

Required Methods

fn relate(&self, from: u64, to: u64, relation: &str) -> Result<u64, MemoryError>

Create a typed edge from -> to. Returns the edge id.

Errors

Returns MemoryError if either endpoint is missing or persistence fails.

fn relations(&self, id: u64) -> Result<Vec<MemoryEdge>, MemoryError>

The outgoing edges of id.

Errors

Returns MemoryError if storage access fails.

fn incoming_relations(&self, id: u64) -> Result<Vec<MemoryEdge>, MemoryError>

The incoming edges of id — the mirror of Self::relations, with the same liveness rule applied to the far end (here the source).

Errors

Returns MemoryError if storage access fails.

fn relations_bounded( &self, id: u64, cap: usize, ) -> Result<BoundedMemoryEdges, MemoryError>

At most cap outgoing edges of id, plus whether its total degree exceeded the scan — the bounded twin of Self::relations (#1820).

The contract is on COST, not just shape: an implementation must keep work and transient allocation O(cap), never O(degree) — a super-node (an entity hub mentioned by thousands of facts) is exactly where this accessor is reached for. truncated is a separate signal because edges.len() == cap cannot carry it: a node with exactly cap edges is indistinguishable from a truncated one.

Errors

Returns MemoryError if storage access fails.

fn incoming_relations_bounded( &self, id: u64, cap: usize, ) -> Result<BoundedMemoryEdges, MemoryError>

At most cap incoming edges of id, plus whether its total incoming degree exceeded the scan — the mirror of Self::relations_bounded, same O(cap) cost contract.

Errors

Returns MemoryError if storage access fails.

fn unrelate(&self, edge_id: u64) -> Result<bool, MemoryError>

Remove the edge with edge_id. Returns true when it existed — idempotent: removing an absent edge is Ok(false), never an error.

Errors

Returns MemoryError if storage access fails.

Provided Methods

fn unrelate_from(&self, from: u64, edge_id: u64) -> Result<bool, MemoryError>

Remove an edge while preserving its known source for mutation capture.

The default keeps third-party backends source-compatible. Native online migration overrides it so OutgoingEdges(from) is recorded before the edge is removed.

Errors

Returns MemoryError if storage access fails.

fn edge_count(&self) -> Option<usize>

The total number of graph edges, when the backend can answer without materializing them — the observable difference between a store whose why() can walk somewhere and one where it degrades to plain similarity search.

Defaulted to None (“cannot say”) rather than required, deliberately: a backend outside this crate (velesdb-wasm’s in-memory store) must keep compiling when this surface grows, and a wrong-but-cheap answer here would flag healthy graphs as flat. memory_status reports the distinction to the caller instead of papering over it.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors

impl GraphStore for NativeStore

Available on crate feature persistence only.