Enum ScalarExpr 

pub enum ScalarExpr {
    Literal(Value),
    Column(ColumnName),
    Upper(Box<ScalarExpr>),
    Lower(Box<ScalarExpr>),
    Length(Box<ScalarExpr>),
    Trim(Box<ScalarExpr>),
    Concat(Vec<ScalarExpr>),
    Abs(Box<ScalarExpr>),
    Round(Box<ScalarExpr>),
    RoundScale(Box<ScalarExpr>, i32),
    Ceil(Box<ScalarExpr>),
    Floor(Box<ScalarExpr>),
    Coalesce(Vec<ScalarExpr>),
    Nullif(Box<ScalarExpr>, Box<ScalarExpr>),
    Cast(Box<ScalarExpr>, DataType),
    Mod(Box<ScalarExpr>, Box<ScalarExpr>),
    Power(Box<ScalarExpr>, Box<ScalarExpr>),
    Sqrt(Box<ScalarExpr>),
    Substring(Box<ScalarExpr>, SubstringRange),
    Extract(DateField, Box<ScalarExpr>),
    DateTrunc(DateField, Box<ScalarExpr>),
    Now,
    CurrentTimestamp,
    CurrentDate,
}

A scalar expression that evaluates to a Value against a row.

Pressurecraft: pure over its inputs (no IO, no clocks, no RNG). Every variant’s evaluation is deterministic — same inputs produce the same output. VOPR-safe.

Variants

Literal(Value)

Literal value.

Column(ColumnName)

Reference to a row column by name.

Upper(Box<ScalarExpr>)

UPPER(s) — ASCII-preserving uppercase via Unicode simple mapping.

Lower(Box<ScalarExpr>)

LOWER(s) — Unicode simple lowercase.

Length(Box<ScalarExpr>)

LENGTH(s) — character count (not byte count).

Trim(Box<ScalarExpr>)

TRIM(s) — strip ASCII whitespace from both ends.

Concat(Vec<ScalarExpr>)

CONCAT(a, b, …) — string concatenation. A NULL operand makes the whole result NULL (PostgreSQL-compatible, differs from MySQL).

Abs(Box<ScalarExpr>)

ABS(n) — absolute value. Preserves the integer subtype when the argument is an integer; returns Real for Real; returns Decimal (same scale) for Decimal.

Round(Box<ScalarExpr>)

ROUND(x) — half-away-from-zero. For integers this is identity.

RoundScale(Box<ScalarExpr>, i32)

ROUND(x, scale) — round to scale decimal places. Only meaningful for Real / Decimal operands; integer operands are returned unchanged.

Ceil(Box<ScalarExpr>)

CEIL(x) / CEILING(x) — least integer >= x.

Floor(Box<ScalarExpr>)

FLOOR(x) — greatest integer <= x.

Coalesce(Vec<ScalarExpr>)

COALESCE(e1, e2, …) — first non-NULL argument, or NULL.

Nullif(Box<ScalarExpr>, Box<ScalarExpr>)

NULLIF(a, b) — NULL if a == b, otherwise a.

Cast(Box<ScalarExpr>, DataType)

CAST(x AS T) — convert x to the target DataType.

NULL in → NULL out for every target. Overflow on narrowing integer casts and unparseable strings surface as QueryError::TypeMismatch rather than silent truncation.

Mod(Box<ScalarExpr>, Box<ScalarExpr>)

MOD(a, b) — remainder of integer division. MOD(_, 0) → NULL per Postgres semantics. AUDIT-2026-05 S3.7.

Power(Box<ScalarExpr>, Box<ScalarExpr>)

POWER(base, exp) — base^exp. Returns Real for any real operand or non-integer exponent; integer-only inputs round-trip through i64 and saturate on overflow. AUDIT-2026-05 S3.7.

Sqrt(Box<ScalarExpr>)

SQRT(x) — square root. Negative input returns QueryError::DomainError. AUDIT-2026-05 S3.7.

Substring(Box<ScalarExpr>, SubstringRange)

SUBSTRING(s FROM start [FOR length]) with the SubstringRange domain primitive carrying the SQL 1-based / negative-start semantics. AUDIT-2026-05 S3.8.

Extract(DateField, Box<ScalarExpr>)

EXTRACT(field FROM ts) — pull a calendar component from a Date or Timestamp. Field set is the closed DateField enum. AUDIT-2026-05 S3.7.

DateTrunc(DateField, Box<ScalarExpr>)

DATE_TRUNC('field', ts) — truncate timestamp to the start of the field interval. Accepts only the truncatable subset of DateField (Year/Month/Day/Hour/Minute/Second). AUDIT-2026-05 S3.7.

Now

NOW() — current statement-stable timestamp. The plan-time fold_time_constants pass replaces this variant with a Literal(Timestamp) before execution; if the evaluator ever sees a bare Now, that’s a planner bug and we panic loudly. AUDIT-2026-05 S3.7.

CurrentTimestamp

CURRENT_TIMESTAMP — alias of NOW() per SQL standard; distinct variant only because some test fixtures want to pin the exact spelling. Same plan-time fold contract.

CurrentDate

CURRENT_DATE — current date, statement-stable. Plan-time folded to Literal(Date(days_since_epoch)).

Trait Implementations

impl Clone for ScalarExpr

fn clone(&self) -> ScalarExpr

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ScalarExpr

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

Formats the value using the given formatter.