Struct DirectReadProjection 

pub struct DirectReadProjection {
    pub leaf_fields: usize,
    pub limit: Option<u32>,
    pub nested: Vec<DirectReadProjection>,
}

A direct read’s projection, in the shape the cost estimator scores it.

The leaf fields this level materialises, the page it materialises them over, and every level composed into the same statement beneath it.

Every read this codebase issues today is flat — leaves, a page, no nesting — and scores exactly what a bare field count scored before this type existed. The nesting is here because the REST ?select= fan-out is to be composed into the parent statement with LATERAL, and a composed statement materialises its embedded levels itself. Handed to a flat estimator it would be charged for the parent’s own columns alone, and per_request_max would loosen by whatever the embed adds — silently, because the number the operator wrote would not have changed.

Fields

leaf_fields: usize

Scalar fields projected at this level.

limit: Option<u32>

The page this level is read over. None is an unpaginated read and scores a multiplier of 1, for the reason given on estimate_direct_read_cost.

nested: Vec<DirectReadProjection>

The levels composed into the same statement beneath this one, each with its own page — which is the point of LATERAL: the embedded ORDER BY/LIMIT live inside the subquery, so a nested level’s page is genuinely its own and not a share of the parent’s.

Implementations

impl DirectReadProjection

pub const fn flat(leaf_fields: usize, limit: Option<u32>) -> Self

A projection with nothing composed beneath it.

leaf_fields scalars over one page — the shape of every direct read today.

Trait Implementations

impl Clone for DirectReadProjection

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for DirectReadProjection

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

Formats the value using the given formatter.

impl Default for DirectReadProjection

fn default() -> Self

Returns the “default value” for a type.

impl Eq for DirectReadProjection

impl PartialEq for DirectReadProjection

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for DirectReadProjection