Enum WindowFunction 

pub enum WindowFunction {
    RowNumber,
    Rank,
    DenseRank,
    Lag {
        offset: usize,
        default: Option<Value>,
    },
    Lead {
        offset: usize,
        default: Option<Value>,
    },
    FirstValue,
    LastValue,
    NthValue {
        n: usize,
    },
}

A window function to evaluate over partitioned, ordered rows.

Variants

RowNumber

ROW_NUMBER() — 1-based sequential ordinal within the partition.

Rank

RANK() — competition ranking with gaps after ties.

DenseRank

DENSE_RANK() — ranking without gaps after ties.

Lag

LAG(expr[, offset[, default]]).

Fields

offset: usize

Number of rows to look backward (defaults to 1 in the constructor).

default: Option<Value>

Value to use when the lookup falls before the partition start.

Lead

LEAD(expr[, offset[, default]]).

Fields

offset: usize

Number of rows to look forward (defaults to 1 in the constructor).

default: Option<Value>

Value to use when the lookup falls past the partition end.

FirstValue

FIRST_VALUE(expr) — first value of expr in the sorted partition.

LastValue

LAST_VALUE(expr) — last value of expr in the sorted partition.

NthValue

NTH_VALUE(expr, n) — the n-th (1-based) value in the sorted partition.

Fields

n: usize

1-based position to fetch; 0 is treated as out of range.

Implementations

impl WindowFunction

pub fn lag() -> Self

LAG(expr) with the default offset of 1 and a NULL fallback.

pub fn lag_offset(offset: usize) -> Self

LAG(expr, offset) with a NULL fallback.

pub fn lag_offset_default(offset: usize, default: Value) -> Self

LAG(expr, offset, default).

pub fn lead() -> Self

LEAD(expr) with the default offset of 1 and a NULL fallback.

pub fn lead_offset(offset: usize) -> Self

LEAD(expr, offset) with a NULL fallback.

pub fn lead_offset_default(offset: usize, default: Value) -> Self

LEAD(expr, offset, default).

pub fn nth_value(n: usize) -> Self

NTH_VALUE(expr, n).

pub fn reads_target(&self) -> bool

Whether the function reads a target column (LAG/LEAD/*_VALUE).

Ranking functions (ROW_NUMBER, RANK, DENSE_RANK) ignore the target column entirely.

Trait Implementations

impl Clone for WindowFunction

fn clone(&self) -> WindowFunction

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for WindowFunction

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

Formats the value using the given formatter.

impl PartialEq for WindowFunction

fn eq(&self, other: &WindowFunction) -> 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 WindowFunction