Method read_tile_as_of

nodedb-array/src/segment/reader.rs:182–213

Reverse-scan tile entries with the given `hilbert_prefix` and `system_from_ms <= system_as_of`, returning the newest qualifying tile version. Returns `Ok(None)` if no version exists at or before the cutoff. The `valid_at_ms` parameter is reserved for the query layer (Tier 9.2). At the reader level, valid-time filtering is NOT applied — the whole tile is returned. This keeps the reader cell-shape

(
        &self,
        hilbert_prefix: u64,
        system_as_of: i64,
        _valid_at_ms: Option<i64>,
    )

    /// 9.2). At the reader level, valid-time filtering is NOT applied —
    /// the whole tile is returned. This keeps the reader cell-shape-agnostic.
    pub fn read_tile_as_of(
        &self,
        hilbert_prefix: u64,
        system_as_of: i64,
        _valid_at_ms: Option<i64>,
    ) -> ArrayResult<Option<TilePayload>> {
        let tiles = &self.footer.tiles;

        // Binary search for the first entry with hilbert_prefix.
        let first = tiles.partition_point(|e| e.tile_id.hilbert_prefix < hilbert_prefix);
        // Binary search for the first entry past the range:
        // hilbert_prefix matches and system_from_ms <= system_as_of.
        // Upper bound: first entry where prefix > hilbert_prefix.
        let past_prefix = tiles.partition_point(|e| e.tile_id.hilbert_prefix <= hilbert_prefix);

        // Slice of entries with matching prefix.
        let candidates = &tiles[first..past_prefix];
        if candidates.is_empty() {
            return Ok(None);
        }

        // Within the prefix slice, entries are ordered by system_from_ms ascending.
        // Find the rightmost entry with system_from_ms <= system_as_of.
        let cutoff_pos = candidates.partition_point(|e| e.tile_id.system_from_ms <= system_as_of);
        if cutoff_pos == 0 {
            return Ok(None);
        }

        // The entry at cutoff_pos - 1 is the newest qualifying version.
        let entry_idx = first + cutoff_pos - 1;
        self.read_tile(entry_idx).map(Some)
    }

    /// Returns an iterator over all tile versions for `hilbert_prefix` whose
    /// `system_from_ms <= system_as_of`, ordered **newest-first** by