Struct Ancestor 

#[non_exhaustive]
pub struct Ancestor {
    pub branch_id: String,
    pub dist: i64,
    pub cutoff: Option<String>,
}

One resolved ancestor of a lineage, nearest first.

Public here rather than in graph because it is a fact about the register this module owns, and because the two functions that take one — crate::temporal::resolve_beliefs and crate::temporal::reconstruct_on — are read-path answers about a branch. Obtain one from Database::ancestry; the crate resolves it from branches and nothing else can construct it correctly (0.15.17, D-259).

One resolved ancestor: exactly the three columns the recursive ancestry_cte produced until 0.15.17.

Public through crate::branch as the answer reconstruct_on resolves over, which is review C-10: until 0.15.17 the resolution rule existed only as SQL, so a caller holding a Vec<EdgeBelief> had no function to finish the question the fold started.

Usually read, occasionally built (0.15.17, D-255)

#[non_exhaustive], and new is the way in — a fourth column is plausible (the fork’s own created_at has been wanted twice) and a struct literal outside this crate would make it a major version.

Almost every caller reads one: Database::ancestry resolves it out of branches, refusing an unregistered lineage first, and resolve_beliefs consumes what it returned. The constructor exists for the caller who is exercising that pure function rather than a database, which is a real case — it is what this crate’s own test for it does — and is worth naming, because an ancestry assembled by hand is a distance rule the caller has stated and resolve_beliefs will apply as faithfully as it applies a resolved one.

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

branch_id: String

The lineage.

dist: i64

Steps from the reader: 0 is the reader itself.

cutoff: Option<String>

The instant past which this ancestor’s rows are not visible, or None for the reader, which has no cutoff.

Implementations

impl Ancestor

pub fn new(branch_id: impl Into<String>, dist: i64) -> Self

One ancestor at dist steps up the parent chain, uncut.

cutoff is None, which is the reader’s own row and the only shape with no fork point above it; cutoff sets it for the rest. Two arguments and a setter rather than three arguments, because the third is an Option that is None on exactly one row of every ancestry and a positional None at every call site reads as a decision nobody made.

Building one states a distance rule rather than reporting a resolved one. crate::Database::ancestry is what to use against a real ledger.

pub fn cutoff(self, ts: impl Into<String>) -> Self

Cut this ancestor at ts.

Trait Implementations

impl Clone for Ancestor

fn clone(&self) -> Ancestor

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Ancestor

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for Ancestor

impl PartialEq for Ancestor

fn eq(&self, other: &Ancestor) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Ancestor