Struct datafusion_common::FunctionalDependence

pub struct FunctionalDependence {
    pub source_indices: Vec<usize>,
    pub target_indices: Vec<usize>,
    pub nullable: bool,
    pub mode: Dependency,
}

This object defines a functional dependence in the schema. A functional dependence defines a relationship between determinant keys and dependent columns. A determinant key is a column, or a set of columns, whose value uniquely determines values of some other (dependent) columns. If two rows have the same determinant key, dependent columns in these rows are necessarily the same. If the determinant key is unique, the set of dependent columns is equal to the entire schema and the determinant key can serve as a primary key. Note that a primary key may “downgrade” into a determinant key due to an operation such as a join, and this object is used to track dependence relationships in such cases. For more information on functional dependencies, see: https://www.scaler.com/topics/dbms/functional-dependency-in-dbms/

Fields

source_indices: Vec<usize>

target_indices: Vec<usize>

nullable: bool

Flag indicating whether one of the source_indices can receive NULL values. For a data source, if the constraint in question is Constraint::Unique, this flag is true. If the constraint in question is Constraint::PrimaryKey, this flag is false. Note that as the schema changes between different stages in a plan, such as after LEFT JOIN or RIGHT JOIN operations, this property may change.

mode: Dependency

Implementations

impl FunctionalDependence

pub fn new( source_indices: Vec<usize>, target_indices: Vec<usize>, nullable: bool ) -> Self

pub fn with_mode(self, mode: Dependency) -> Self

Trait Implementations

impl Clone for FunctionalDependence

fn clone(&self) -> FunctionalDependence

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for FunctionalDependence

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

Formats the value using the given formatter.

impl PartialEq<FunctionalDependence> for FunctionalDependence

fn eq(&self, other: &FunctionalDependence) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for FunctionalDependence

impl StructuralEq for FunctionalDependence

impl StructuralPartialEq for FunctionalDependence