Enum ScalarExpr 

pub enum ScalarExpr<F> {
    Column(F),
    Literal(Literal),
    Binary {
        left: Box<ScalarExpr<F>>,
        op: BinaryOp,
        right: Box<ScalarExpr<F>>,
    },
    Not(Box<ScalarExpr<F>>),
    IsNull {
        expr: Box<ScalarExpr<F>>,
        negated: bool,
    },
    Aggregate(AggregateCall<F>),
    GetField {
        base: Box<ScalarExpr<F>>,
        field_name: String,
    },
    Cast {
        expr: Box<ScalarExpr<F>>,
        data_type: DataType,
    },
    Compare {
        left: Box<ScalarExpr<F>>,
        op: CompareOp,
        right: Box<ScalarExpr<F>>,
    },
    Coalesce(Vec<ScalarExpr<F>>),
    ScalarSubquery(ScalarSubqueryExpr),
    Case {
        operand: Option<Box<ScalarExpr<F>>>,
        branches: Vec<(ScalarExpr<F>, ScalarExpr<F>)>,
        else_expr: Option<Box<ScalarExpr<F>>>,
    },
    Random,
}

Arithmetic scalar expression that can reference multiple fields.

Variants

Column(F)

Literal(Literal)

Binary

Fields

left: Box<ScalarExpr<F>>

op: BinaryOp

right: Box<ScalarExpr<F>>

Not(Box<ScalarExpr<F>>)

Logical NOT returning 1 for falsey inputs, 0 for truthy inputs, and NULL for NULL inputs.

IsNull

NULL test returning 1 when the operand is NULL (or NOT NULL when negated is true) and 0 otherwise. Returns NULL when the operand cannot be determined.

Fields

expr: Box<ScalarExpr<F>>

negated: bool

Aggregate(AggregateCall<F>)

Aggregate function call (e.g., COUNT(), SUM(col), etc.) This is used in expressions like COUNT() + 1

GetField

Extract a field from a struct expression. For example: user.address.city would be represented as GetField { base: GetField { base: Column(user), field_name: “address” }, field_name: “city” }

Fields

base: Box<ScalarExpr<F>>

field_name: String

Cast

Explicit type cast to an Arrow data type.

Fields

expr: Box<ScalarExpr<F>>

data_type: DataType

Compare

Comparison producing a boolean (1/0) result.

Fields

left: Box<ScalarExpr<F>>

op: CompareOp

right: Box<ScalarExpr<F>>

Coalesce(Vec<ScalarExpr<F>>)

First non-null expression in the provided list.

ScalarSubquery(ScalarSubqueryExpr)

Scalar subquery evaluated per input row.

Case

SQL CASE expression with optional operand and ELSE branch.

Fields

operand: Option<Box<ScalarExpr<F>>>

Optional operand for simple CASE (e.g., CASE x WHEN ...).

branches: Vec<(ScalarExpr<F>, ScalarExpr<F>)>

Ordered (WHEN, THEN) branches.

else_expr: Option<Box<ScalarExpr<F>>>

Optional ELSE result.

Random

Random number generator returning a float in [0.0, 1.0).

Follows the PostgreSQL/DuckDB standard: each evaluation produces a new pseudo-random value. No seed control is exposed at the SQL level.

Implementations

impl<F> ScalarExpr<F>

pub fn column(field: F) -> Self

pub fn literal<L: Into<Literal>>(lit: L) -> Self

pub fn binary(left: Self, op: BinaryOp, right: Self) -> Self

pub fn logical_not(expr: Self) -> Self

pub fn is_null(expr: Self, negated: bool) -> Self

pub fn aggregate(call: AggregateCall<F>) -> Self

pub fn get_field(base: Self, field_name: String) -> Self

pub fn cast(expr: Self, data_type: DataType) -> Self

pub fn compare(left: Self, op: CompareOp, right: Self) -> Self

pub fn coalesce(exprs: Vec<Self>) -> Self

pub fn scalar_subquery(id: SubqueryId, data_type: DataType) -> Self

pub fn case( operand: Option<Self>, branches: Vec<(Self, Self)>, else_expr: Option<Self>, ) -> Self

pub fn random() -> Self

impl<F> ScalarExpr<F>

where F: Display + Copy,

pub fn format_display(&self) -> String

Render a scalar expression as a human-readable string.

Trait Implementations

impl<F: Clone> Clone for ScalarExpr<F>

fn clone(&self) -> ScalarExpr<F>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<F: Debug> Debug for ScalarExpr<F>

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

Formats the value using the given formatter.