Struct Layout 

pub struct Layout {
    pub file: u64,
    pub rows: usize,
    pub stripes: usize,
    pub parts: usize,
    pub columns: Vec<ColumnLayout>,
    pub indexes: u64,
    pub directory: u64,
    pub header: u64,
}

Where a whole file’s bytes went.

Every number here comes out of the committed directory, so taking it costs one directory read however large the file is. That is the point: a 45 GB table has to be able to say where it went without being read, or nobody will ask.

The parts that are not a column are kept apart rather than shared out over the columns. The stripe index page holds a section per column and could be split, and the directory and the header cannot be, so splitting one of the three and not the others would read as if the columns accounted for everything. They do not, and the gap is the thing worth looking at.

Fields

file: u64

The size of the file on disk.

rows: usize

Committed rows.

stripes: usize

Committed stripes.

parts: usize

Committed parts, which is how many chunks a scan reads.

columns: Vec<ColumnLayout>

One entry per column, in the table’s column order.

indexes: u64

Every stripe’s index page, which carries a length and a checksum for every part of every column and is charged per stripe rather than per column.

directory: u64

The committed directory itself, the one that was read to build this.

header: u64

The fixed header, which holds the magic, the format and the two directory slots.

Implementations

impl Layout

pub fn columns_total(&self) -> u64

Everything the columns cost together.

pub fn unaccounted(&self) -> u64

What the file holds that this does not account for.

A committed file is written once and never rewritten in place, so an earlier directory and the pages of an earlier snapshot are still in it. That is the honest place for them: they are bytes on disk that no column owns.

Trait Implementations

impl Clone for Layout

fn clone(&self) -> Layout

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Layout

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

Formats the value using the given formatter.