Struct PermSet 

pub struct PermSet(/* private fields */);

Which permutations a file stores — a 6-bit set over IndexPermutation::section_index, recorded in the header so a reader never has to assume six.

Every legal set is a superset of PermSet::CORE = {SPO, POS, OSP}. That is not a convention: those three tie the longest bound prefix on all eight triple-pattern shapes, so GraphIndex::best_permutation never selects outside them and a lean file routes every pattern exactly where a full one does — same tiles, same rows. What the other three (SOP, PSO, OPS) add is a sort order: they let GraphIndex::permutation_sorted_on hand a sort-merge join a co-sorted stream for three of the twelve (bound-set, join-column) shapes it otherwise has to hash-join. Absent, the merge seed declines and the hash path answers — the cost is a fast path, never correctness (bgp::try_merge_join already returns Option).

CORE is the smallest legal set, PermSet::ALL is the default and what every file written before this existed carries.

Implementations

impl PermSet

pub const ALL: PermSet

All six permutations — the default, and what a 0 header byte means.

pub const CORE: PermSet

The three routing permutations {SPO, POS, OSP}: every pattern shape routes as well as it does with six, no merge-join sort orders.

pub fn from_bits(bits: u8) -> Result<PermSet, &'static str>

Parse a raw mask. Err when it is not a superset of PermSet::CORE or addresses a permutation this build has no section index for — a pattern would then route to a permutation the file does not carry, which is the one failure mode that must never be silent.

pub fn bits(self) -> u8

The raw 6-bit mask.

pub fn contains(self, perm: IndexPermutation) -> bool

Is perm stored in this file?

pub fn len(self) -> usize

How many permutation sections the file’s index container holds.

pub fn is_empty(self) -> bool

Never true: every legal set contains PermSet::CORE. Present because a public len without it is a clippy error, and the honest answer is more useful than an allow.

pub fn iter(self) -> impl Iterator<Item = IndexPermutation>

The stored permutations in [ALL_PERMS] (= container) order.

pub fn position(self, perm: IndexPermutation) -> Option<usize>

perm’s position inside the index container, which is its rank among the stored permutations — not IndexPermutation::section_index, which is its slot in the format’s fixed six-wide addressing. The two coincide only for PermSet::ALL.

pub fn names(self) -> Vec<&'static str>

Names in container order, e.g. ["SPO", "POS", "OSP"].

pub fn has_merge_orders(self) -> bool

Does this set carry the three merge-join orders?

Trait Implementations

impl Clone for PermSet

fn clone(&self) -> PermSet

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for PermSet

impl Debug for PermSet

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

Formats the value using the given formatter.

impl Default for PermSet

fn default() -> PermSet

Returns the “default value” for a type.

impl Eq for PermSet

impl Hash for PermSet

fn hash<__H>(&self, state: &mut __H)

where __H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for PermSet

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for PermSet