[−][src]Trait differential_dataflow::operators::join::Join

pub trait Join<G: Scope, K: Data, V: Data, R: Semigroup> {
    fn join_map<V2, R2, D, L>(
        &self, 
        other: &Collection<G, (K, V2), R2>, 
        logic: L
    ) -> Collection<G, D, <R as Mul<R2>>::Output>
    where
        K: ExchangeData,
        V2: ExchangeData,
        R2: ExchangeData + Semigroup,
        R: Mul<R2>,
        <R as Mul<R2>>::Output: Semigroup,
        D: Data,
        L: FnMut(&K, &V, &V2) -> D + 'static;

    fn semijoin<R2>(
        &self, 
        other: &Collection<G, K, R2>
    ) -> Collection<G, (K, V), <R as Mul<R2>>::Output>
    where
        K: ExchangeData,
        R2: ExchangeData + Semigroup,
        R: Mul<R2>,
        <R as Mul<R2>>::Output: Semigroup;

    fn antijoin<R2>(
        &self, 
        other: &Collection<G, K, R2>
    ) -> Collection<G, (K, V), R>
    where
        K: ExchangeData,
        R2: ExchangeData + Semigroup,
        R: Mul<R2, Output = R>,
        R: Abelian;

    fn join<V2, R2>(
        &self, 
        other: &Collection<G, (K, V2), R2>
    ) -> Collection<G, (K, (V, V2)), <R as Mul<R2>>::Output>
    where
        K: ExchangeData,
        V2: ExchangeData,
        R2: ExchangeData + Semigroup,
        R: Mul<R2>,
        <R as Mul<R2>>::Output: Semigroup,
    { ... }
}

Join implementations for (key,val) data.

Required methods

fn join_map<V2, R2, D, L>(
    &self,
    other: &Collection<G, (K, V2), R2>,
    logic: L
) -> Collection<G, D, <R as Mul<R2>>::Output> where
    K: ExchangeData,
    V2: ExchangeData,
    R2: ExchangeData + Semigroup,
    R: Mul<R2>,
    <R as Mul<R2>>::Output: Semigroup,
    D: Data,
    L: FnMut(&K, &V, &V2) -> D + 'static, 

Matches pairs (key,val1) and (key,val2) based on key and then applies a function.

Examples

extern crate timely;
extern crate differential_dataflow;

use differential_dataflow::input::Input;
use differential_dataflow::operators::Join;

fn main() {
    ::timely::example(|scope| {

        let x = scope.new_collection_from(vec![(0, 1), (1, 3)]).1;
        let y = scope.new_collection_from(vec![(0, 'a'), (1, 'b')]).1;
        let z = scope.new_collection_from(vec![(1, 'a'), (3, 'b')]).1;

        x.join_map(&y, |_key, &a, &b| (a,b))
         .assert_eq(&z);
    });
}

fn semijoin<R2>(
    &self,
    other: &Collection<G, K, R2>
) -> Collection<G, (K, V), <R as Mul<R2>>::Output> where
    K: ExchangeData,
    R2: ExchangeData + Semigroup,
    R: Mul<R2>,
    <R as Mul<R2>>::Output: Semigroup, 

Matches pairs (key, val) and key based on key, producing the former with frequencies multiplied.

When the second collection contains frequencies that are either zero or one this is the more traditional relational semijoin. When the second collection may contain multiplicities, this operation may scale up the counts of the records in the first input.

Examples

extern crate timely;
extern crate differential_dataflow;

use differential_dataflow::input::Input;
use differential_dataflow::operators::Join;

fn main() {
    ::timely::example(|scope| {

        let x = scope.new_collection_from(vec![(0, 1), (1, 3)]).1;
        let y = scope.new_collection_from(vec![0, 2]).1;
        let z = scope.new_collection_from(vec![(0, 1)]).1;

        x.semijoin(&y)
         .assert_eq(&z);
    });
}

fn antijoin<R2>(&self, other: &Collection<G, K, R2>) -> Collection<G, (K, V), R> where
    K: ExchangeData,
    R2: ExchangeData + Semigroup,
    R: Mul<R2, Output = R>,
    R: Abelian, 

Subtracts the semijoin with other from self.

In the case that other has multiplicities zero or one this results in a relational antijoin, in which we discard input records whose key is present in other. If the multiplicities could be other than zero or one, the semantic interpretation of this operator is less clear.

In almost all cases, you should ensure that other has multiplicities that are zero or one, perhaps by using the distinct operator.

Examples

extern crate timely;
extern crate differential_dataflow;

use differential_dataflow::input::Input;
use differential_dataflow::operators::Join;

fn main() {
    ::timely::example(|scope| {

        let x = scope.new_collection_from(vec![(0, 1), (1, 3)]).1;
        let y = scope.new_collection_from(vec![0, 2]).1;
        let z = scope.new_collection_from(vec![(1, 3)]).1;

        x.antijoin(&y)
         .assert_eq(&z);
    });
}
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Provided methods

fn join<V2, R2>(
    &self,
    other: &Collection<G, (K, V2), R2>
) -> Collection<G, (K, (V, V2)), <R as Mul<R2>>::Output> where
    K: ExchangeData,
    V2: ExchangeData,
    R2: ExchangeData + Semigroup,
    R: Mul<R2>,
    <R as Mul<R2>>::Output: Semigroup, 

Matches pairs (key,val1) and (key,val2) based on key and then applies a function.

Examples

extern crate timely;
extern crate differential_dataflow;

use differential_dataflow::input::Input;
use differential_dataflow::operators::Join;

fn main() {
    ::timely::example(|scope| {

        let x = scope.new_collection_from(vec![(0, 1), (1, 3)]).1;
        let y = scope.new_collection_from(vec![(0, 'a'), (1, 'b')]).1;
        let z = scope.new_collection_from(vec![(0, (1, 'a')), (1, (3, 'b'))]).1;

        x.join(&y)
         .assert_eq(&z);
    });
}
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Implementors

impl<G, K, V, R> Join<G, K, V, R> for Collection<G, (K, V), R> where
    G: Scope,
    K: ExchangeData + Hashable,
    V: ExchangeData,
    R: ExchangeData + Semigroup,
    G::Timestamp: Lattice + Ord, [src]

impl<G, Tr> Join<G, <Tr as TraceReader>::Key, <Tr as TraceReader>::Val, <Tr as TraceReader>::R> for Arranged<G, Tr> where
    G: Scope,
    G::Timestamp: Lattice + Ord,
    Tr: TraceReader<Time = G::Timestamp> + Clone + 'static,
    Tr::Key: Data + Hashable,
    Tr::Val: Data,
    Tr::R: Semigroup,
    Tr::Batch: BatchReader<Tr::Key, Tr::Val, G::Timestamp, Tr::R> + 'static,
    Tr::Cursor: Cursor<Tr::Key, Tr::Val, G::Timestamp, Tr::R> + 'static, [src]

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