Struct ForeignKeyConstraint 

pub struct ForeignKeyConstraint { /* private fields */ }

Foreign key constraint for validating referential integrity between tables.

This constraint ensures that all non-null values in a child table’s foreign key column exist as values in the parent table’s referenced column. It’s essential for maintaining data consistency and preventing orphaned records.

The constraint supports:

• Inner and left joins for different validation strategies
• Null value handling (allow/disallow nulls in foreign key)
• Custom error messages and violation reporting
• Performance optimization through predicate pushdown

Implementations

impl ForeignKeyConstraint

pub fn new( child_column: impl Into<String>, parent_column: impl Into<String>, ) -> Self

Create a new foreign key constraint.

Arguments

• child_column - Column in child table containing foreign key values
• parent_column - Column in parent table containing referenced values

Examples

use term_guard::constraints::ForeignKeyConstraint;

let fk = ForeignKeyConstraint::new("orders.customer_id", "customers.id");

pub fn allow_nulls(self, allow: bool) -> Self

Set whether to allow NULL values in the foreign key column.

When true, NULL values in the child column are considered valid. When false, NULL values are treated as constraint violations.

pub fn use_left_join(self, use_left_join: bool) -> Self

Set the join strategy for validation.

• true (default): Use LEFT JOIN strategy, better for tables with few violations
• false: Use NOT EXISTS strategy, better for tables with many violations

pub fn max_violations_reported(self, max_violations: usize) -> Self

Set the maximum number of violation examples to report.

Defaults to 100. Set to 0 to disable violation example collection.

pub fn child_column(&self) -> &str

Get the child column name

pub fn parent_column(&self) -> &str

Get the parent column name

Trait Implementations

impl Clone for ForeignKeyConstraint

fn clone(&self) -> ForeignKeyConstraint

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Constraint for ForeignKeyConstraint

fn evaluate<'life0, 'life1, 'async_trait>( &'life0 self, ctx: &'life1 SessionContext, ) -> Pin<Box<dyn Future<Output = Result<ConstraintResult>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait, 'life1: 'async_trait,

Evaluates the constraint against the data in the session context.

fn name(&self) -> &str

Returns the name of the constraint.

fn column(&self) -> Option<&str>

Returns the column this constraint operates on (if single-column).

fn description(&self) -> Option<&str>

Returns a description of what this constraint validates.

fn metadata(&self) -> ConstraintMetadata

Returns the metadata associated with this constraint.

impl Debug for ForeignKeyConstraint

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for ForeignKeyConstraint

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Serialize for ForeignKeyConstraint

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.