Struct mz_expr::JoinInputCharacteristics

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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>,
}
Expand description

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.

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§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§

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impl JoinInputCharacteristics

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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.

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pub fn explain(&self) -> String

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

Trait Implementations§

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impl Clone for JoinInputCharacteristics

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fn clone(&self) -> JoinInputCharacteristics

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl Debug for JoinInputCharacteristics

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

Formats the value using the given formatter. Read more
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impl<'de> Deserialize<'de> for JoinInputCharacteristics

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fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>
where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer. Read more
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impl Hash for JoinInputCharacteristics

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

Feeds this value into the given Hasher. Read more
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fn hash_slice<H>(data: &[Self], state: &mut H)
where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher. Read more
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impl MzReflect for JoinInputCharacteristics

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fn add_to_reflected_type_info(rti: &mut ReflectedTypeInfo)

Adds names and types of the fields of the struct or enum to rti. Read more
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impl Ord for JoinInputCharacteristics

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

This method returns an Ordering between self and other. Read more
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fn max(self, other: Self) -> Self
where Self: Sized,

Compares and returns the maximum of two values. Read more
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fn min(self, other: Self) -> Self
where Self: Sized,

Compares and returns the minimum of two values. Read more
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fn clamp(self, min: Self, max: Self) -> Self
where Self: Sized + PartialOrd,

Restrict a value to a certain interval. Read more
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impl PartialEq for JoinInputCharacteristics

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

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

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

This method returns an ordering between self and other values if one exists. Read more
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fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator. Read more
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fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more
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fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator. Read more
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fn ge(&self, other: &Rhs) -> bool

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

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

Serialize this value into the given Serde serializer. Read more
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impl Eq for JoinInputCharacteristics

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impl StructuralPartialEq for JoinInputCharacteristics

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