Enum UniqueConstraintStrategy 

#[non_exhaustive]
pub enum UniqueConstraintStrategy {
    DeleteDuplicates {
        keep: KeepPolicy,
    },
}

How AddConstraint(Unique) should handle pre-existing duplicate rows.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

DeleteDuplicates

Emit a DELETE statement just before the ADD CONSTRAINT so only one row per group of duplicates survives. keep picks which one. This is the only strategy in v0.2 — see module docs.

Fields

keep: KeepPolicy

Which row of each duplicate group is preserved. See KeepPolicy.

Trait Implementations

impl Clone for UniqueConstraintStrategy

fn clone(&self) -> UniqueConstraintStrategy

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for UniqueConstraintStrategy

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

Formats the value using the given formatter.

impl Default for UniqueConstraintStrategy

fn default() -> Self

Default strategy is DeleteDuplicates { keep: First }: keep the row with the smallest primary-key value of each duplicate group. This is what wire-format-omitted strategy (v0.1.x migrations or any JSON without the field) deserializes to.

Wire-format breaking change vs v0.1.x. v0.1.x emitted no pre-cleanup and let the database reject the migration. v0.2 emits a DELETE automatically. Existing migrations that already applied under v0.1.x are unaffected (apply happens once); v0.1.x migrations re-run against a fresh DB will now drop duplicate rows instead of failing.

impl<'de> Deserialize<'de> for UniqueConstraintStrategy

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

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for UniqueConstraintStrategy

impl Hash for UniqueConstraintStrategy

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl JsonSchema for UniqueConstraintStrategy

fn schema_name() -> Cow<'static, str>

The name of the generated JSON Schema.

fn schema_id() -> Cow<'static, str>

Returns a string that uniquely identifies the schema produced by this type.

fn json_schema(generator: &mut SchemaGenerator) -> Schema

Generates a JSON Schema for this type.

fn inline_schema() -> bool

Whether JSON Schemas generated for this type should be included directly in parent schemas, rather than being re-used where possible using the $ref keyword.

impl Ord for UniqueConstraintStrategy

fn cmp(&self, other: &UniqueConstraintStrategy) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for UniqueConstraintStrategy

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

Tests for self and other values to be equal, and is used by ==.

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

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

impl PartialOrd for UniqueConstraintStrategy

fn partial_cmp(&self, other: &UniqueConstraintStrategy) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

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

Tests less than (for self and other) and is used by the < operator.

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

Tests less than or equal to (for self and other) and is used by the <= operator.

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

Tests greater than (for self and other) and is used by the > operator.

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

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl Serialize for UniqueConstraintStrategy

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

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for UniqueConstraintStrategy