Module scalar_fn 

Scalar function vtable machinery.

This module contains the ScalarFnVTable trait and all built-in scalar function implementations. Expressions (crate::expr::Expression) reference scalar functions at each node.

Strict functions with row-at-a-time kernels can implement unstable::row::RowFn. It handles decoding, constants, null propagation, output construction, and validity. This API requires the unstable_row_fns feature and has no compatibility guarantees. Implement ScalarFnVTable directly for columnar kernels and functions that alias an input or can produce null from valid inputs.

Modules

fns

internal

session

unstable

Experimental scalar-function APIs without compatibility guarantees.

Structs

ArrayReduceNode

A ReduceNode over an array tree.

EmptyOptions

ExpressionReduceNode

A ReduceNode over an expression tree, typed within a scope.

ForeignScalarFnOptions

Options payload for a foreign scalar function.

ForeignScalarFnVTable

Scalar function placeholder used when deserializing an unknown scalar function ID.

ScalarFnOptions

An opaque handle to expression options.

ScalarFnRef

A type-erased scalar function, pairing a vtable with bound options behind a trait object.

ScalarFnSignature

Information about the signature of an expression.

TypedScalarFnInstance

A typed scalar function instance, parameterized by a concrete ScalarFnVTable.

VecExecutionArgs

A concrete ExecutionArgs backed by a Vec<ArrayRef>.

Enums

Arity

The arity (number of arguments) of a function.

Traits

ExecutionArgs

Arguments for expression execution.

ReduceNode

A node used for implementing abstract reduction rules over a tree of scalar functions.

ScalarFnPlugin

Registry trait for ID-based deserialization of scalar functions.

ScalarFnVTable

This trait defines the interface for scalar function vtables, including methods for serialization, deserialization, validation, child naming, return type computation, and evaluation.

ScalarFnVTableExt

Factory functions for vtables.

SimplifyCtx

Context for simplification.

Functions

is_negative_cost

A scalar function has a negative cost if applying it to an array and canonicalizing is cheaper than canonicalizing an array and applying it.

Type Aliases

ChildName

A reference to the name of a child expression.

ScalarFnId

A unique identifier for a scalar function.

ScalarFnPluginRef

Reference-counted pointer to a scalar function plugin.