Enum CountExpr 

#[non_exhaustive]
pub enum CountExpr {
    Literal(usize),
    Parameter(String),
}

A count expression for SKIP/LIMIT: either a resolved literal or an unresolved parameter.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Literal(usize)

A resolved integer count.

Parameter(String)

An unresolved parameter reference (e.g., $limit).

Implementations

impl CountExpr

pub fn value(&self) -> usize

Returns the resolved count, or panics if still a parameter reference.

Call this only after parameter substitution has run.

Panics

Panics if the expression is an unresolved Parameter reference.

pub fn try_value(&self) -> Result<usize, String>

Returns the resolved count, or an error if still a parameter reference.

Errors

Returns an error string if the expression is an unresolved Parameter.

pub fn estimate(&self) -> f64

Returns the count as f64 for cardinality estimation (defaults to 10 for unresolved params).

Trait Implementations

impl Clone for CountExpr

fn clone(&self) -> CountExpr

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for CountExpr

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

Formats the value using the given formatter.

impl Display for CountExpr

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

Formats the value using the given formatter.

impl From<usize> for CountExpr

fn from(n: usize) -> Self

Converts to this type from the input type.

impl PartialEq<usize> for CountExpr

fn eq(&self, other: &usize) -> 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 PartialEq for CountExpr

fn eq(&self, other: &CountExpr) -> 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 Eq for CountExpr

impl StructuralPartialEq for CountExpr