Struct CostEstimate 

#[non_exhaustive]
pub struct CostEstimate { /* private fields */ }

A cost estimate an engine reports to the optimizer, mirroring MySQL’s Cost_estimate.

The first three components are time-consuming costs the optimizer sums to compare access paths: I/O, CPU, and import (remote) cost. The fourth, memory cost, tracks bytes the engine expects to allocate and is kept apart from the time-based total. All four use MySQL’s internal cost units.

Returned as Some from table_scan_cost, index_scan_cost, and read_cost; the shim assembles a Cost_estimate from the components. This is distinct from the opaque crate::sys::CostEstimate, which is a borrowed handle to a live MySQL accumulator the binding cannot construct.

Examples

use mysql_handler::engine::CostEstimate;

let cost = CostEstimate::new(10.0, 2.0, 0.0, 0.0);
assert_eq!(cost.io_cost(), 10.0);
assert_eq!(cost.cpu_cost(), 2.0);

Implementations

impl CostEstimate

pub const fn new( io_cost: f64, cpu_cost: f64, import_cost: f64, mem_cost: f64, ) -> Self

Build a cost estimate from its I/O, CPU, import, and memory components, each in MySQL’s internal cost units.

pub const fn io_cost(&self) -> f64

Cost of the I/O operations the access path performs.

pub const fn cpu_cost(&self) -> f64

Cost of the CPU work the access path performs.

pub const fn import_cost(&self) -> f64

Cost of remote (import) operations the access path performs.

pub const fn mem_cost(&self) -> f64

Memory the access path expects to use, in bytes.

Trait Implementations

impl Clone for CostEstimate

fn clone(&self) -> CostEstimate

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for CostEstimate

impl Debug for CostEstimate

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

Formats the value using the given formatter.

impl PartialEq for CostEstimate

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for CostEstimate