kdrant-core/dev.kdrant.model/Expression

Expression

@Serializable(with = ExpressionSerializer::class)

sealed interface Expression

An arithmetic expression over a point's score and payload, evaluated by Qdrant to rerank the candidates a Prefetch produced.

This is the "boost by business rules" layer: multiply the vector score by a popularity field, add a bonus for points matching a condition, decay by recency or by distance. It runs on the server, over candidates that have already been narrowed, which is what makes it cheap enough to be worth doing.

// relevance, boosted for in-stock items and decayed by how far away the seller is
qdrant.search("products") {
    prefetch { query(queryVector); limit = 100 }
    formula(
        Expression.sum(
            Expression.score,
            Expression.mult(Expression.of(0.5), Expression.condition(filter { must { "in_stock" eq true } })),
            Expression.expDecay(Expression.geoDistance(origin = here, to = "seller_location"), scale = 5_000.0),
        ),
    )
    limit = 10
}

Request-only: Qdrant never returns an expression, so this serializes but does not deserialize.

Inheritors

Types

Abs

data class Abs(val operand: Expression) : Expression

Absolute value.

Companion

object Companion

Condition

data class Condition(val condition: Condition) : Expression

A filter condition as a number: 1.0 when the point matches, 0.0 when it does not.

Datetime

data class Datetime(val value: String) : Expression

An RFC 3339 datetime as a Unix timestamp.

DatetimeKey

data class DatetimeKey(val key: String) : Expression

A payload key holding a datetime, as a Unix timestamp.

Div

data class Div(val left: Expression, val right: Expression, val byZeroDefault: Double? = null) : Expression

left divided by right. byZeroDefault is what the division evaluates to when right is zero; without it Qdrant fails the query rather than inventing a number.

Exp

data class Exp(val operand: Expression) : Expression

Natural exponential.

ExpDecay

data class ExpDecay(val params: DecayParams) : Expression

Exponential decay of params.

GaussDecay

data class GaussDecay(val params: DecayParams) : Expression

Gaussian decay of params.

GeoDistance

data class GeoDistance(val origin: GeoPoint, val to: String) : Expression

Distance in metres from origin to the geo point in the payload field to.

LinDecay

data class LinDecay(val params: DecayParams) : Expression

Linear decay of params.

data class Ln(val operand: Expression) : Expression

Natural logarithm.

Log10

data class Log10(val operand: Expression) : Expression

Base-10 logarithm.

Mult

data class Mult(val operands: List<Expression>) : Expression

The product of every operand.

Neg

data class Neg(val operand: Expression) : Expression

Arithmetic negation.

Pow

data class Pow(val base: Expression, val exponent: Expression) : Expression

base raised to exponent.

Sqrt

data class Sqrt(val operand: Expression) : Expression

Square root.

Sum

data class Sum(val operands: List<Expression>) : Expression

The sum of every operand.

Value

data class Value(val value: Double) : Expression

A constant.

Variable

data class Variable(val name: String) : Expression

A payload key, or one of Qdrant's variables. $score is the vector score of the candidate; a plain key reads that payload field, and a missing field evaluates to the formula's default for that key (see defaults) or fails the query.