Struct mz_expr::JoinInputCharacteristics

pub struct JoinInputCharacteristics {
    pub unique_key: bool,
    pub key_length: usize,
    pub arranged: bool,
    pub cardinality: Option<Reverse<usize>>,
    pub filters: FilterCharacteristics,
    pub input: Reverse<usize>,
}

Characteristics of a join order candidate collection.

A candidate is described by a collection and a key, and may have various liabilities. Primarily, the candidate may risk substantial inflation of records, which is something that concerns us greatly. Additionally the candidate may be unarranged, and we would prefer candidates that do not require additional memory. Finally, we prefer lower id collections in the interest of consistent tie-breaking.

Fields

unique_key: bool

An excellent indication that record count will not increase.

key_length: usize

A weaker signal that record count will not increase.

arranged: bool

Indicates that there will be no additional in-memory footprint.

cardinality: Option<Reverse<usize>>

Estimated cardinality (lower is better)

filters: FilterCharacteristics

Characteristics of the filter that is applied at this input.

input: Reverse<usize>

We want to prefer input earlier in the input list, for stability of ordering.

Implementations

impl JoinInputCharacteristics

pub fn new( unique_key: bool, key_length: usize, arranged: bool, cardinality: Option<usize>, filters: FilterCharacteristics, input: usize ) -> Self

Creates a new instance with the given characteristics.

pub fn explain(&self) -> String

Turns the instance into a String to be printed in EXPLAIN.

Trait Implementations

impl Clone for JoinInputCharacteristics

fn clone(&self) -> JoinInputCharacteristics

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for JoinInputCharacteristics

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for JoinInputCharacteristics

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

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Hash for JoinInputCharacteristics

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 MzReflect for JoinInputCharacteristics

fn add_to_reflected_type_info(rti: &mut ReflectedTypeInfo)

Adds names and types of the fields of the struct or enum to rti.

impl Ord for JoinInputCharacteristics

fn cmp(&self, other: &JoinInputCharacteristics) -> 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 + PartialOrd,

Restrict a value to a certain interval.

impl PartialEq for JoinInputCharacteristics

fn eq(&self, other: &JoinInputCharacteristics) -> 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 PartialOrd for JoinInputCharacteristics

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

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

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

This method tests less than (for self and other) and is used by the < operator.

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

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

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

This method tests greater than (for self and other) and is used by the > operator.

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

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

impl Serialize for JoinInputCharacteristics

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

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl Eq for JoinInputCharacteristics

impl StructuralPartialEq for JoinInputCharacteristics