Struct DependencyGraph 

pub struct DependencyGraph { /* private fields */ }

A directed acyclic graph of migration dependencies.

Implementations

impl DependencyGraph

pub fn build( migrations: &[&ResolvedMigration], implicit_chain: bool, ) -> Result<Self>

Build a dependency graph from resolved migrations.

If implicit_chain is true, each versioned migration implicitly depends on the previous version in sort order (backward-compatible default).

pub fn topological_sort(&self) -> Result<Vec<String>>

Produce a topologically sorted order of versions using Kahn’s algorithm.

Ties — migrations that become runnable at the same moment — are broken by version order, which makes the result deterministic.

This matters more than it looks. The ready set used to be a VecDeque fed from reverse_edges, a HashSet whose iteration order is randomly seeded per process. Five independent migrations therefore applied in a different order on almost every run: the order explain previewed was not the order migrate used, and staging and production disagreed on installed_rank. Any topological order is correct, but only a reproducible one is honest.

Uses borrowed &str references internally to avoid cloning during the sort; only clones into owned Strings for the output.