Struct GroupIndex 

pub struct GroupIndex {
    pub groups: Vec<GroupMeta>,
    pub key_names: Vec<String>,
}

A deterministic group index built from a TidyView.

Groups are created in first-occurrence order: the first time a key combination appears (scanning visible rows in ascending base-row order), a new group entry is appended. This guarantees a stable, reproducible output ordering regardless of hash-map iteration order.

No column buffers are copied during group construction.

Fields

groups: Vec<GroupMeta>

Groups in first-occurrence order.

key_names: Vec<String>

The column names used as group keys (projected names).

Implementations

impl GroupIndex

pub fn build( base: &DataFrame, key_col_indices: &[usize], visible_rows: &[usize], key_names: Vec<String>, ) -> Self

Build a GroupIndex from a materialized set of visible rows.

key_col_indices are indices into base.columns. visible_rows are base-frame row indices in ascending order.

impl GroupIndex

pub fn build_fast<I: IntoIterator<Item = usize>>( base: &DataFrame, key_col_indices: &[usize], visible_rows: I, key_names: Vec<String>, ) -> Self

Build a GroupIndex using a BTree-accelerated lookup.

Semantics: identical to GroupIndex::build(). First-occurrence group ordering is preserved. The only difference is O(N log G) vs O(N × G).

Phase 2 (v3) cat-aware fast path: when every key column is Column::Categorical, the lookup BTreeMap keys are Vec<u32> of category codes instead of Vec<String> of display values. This eliminates levels[code].clone() per row per key column. The fast path is bit-identical to the string path:

• Group slots are still assigned in first-occurrence row order.
• GroupMeta::key_values is still Vec<String> of display values, computed once per group (not once per row).
• Mixed-type keys (e.g., categorical + int) fall back to the string path automatically.

Trait Implementations

impl Clone for GroupIndex

fn clone(&self) -> GroupIndex

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for GroupIndex

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

Formats the value using the given formatter.