@electric-sql/d2mini/dist/multiset.js

D2Mini is a minimal implementation of Differential Dataflow for performing in-memory incremental view maintenance.

import { DefaultMap, chunkedArrayPush, hash } from './utils.js';
/**
 * A multiset of data.
 */
export class MultiSet {
    #inner;
    constructor(data = []) {
        this.#inner = data;
    }
    toString(indent = false) {
        return `MultiSet(${JSON.stringify(this.#inner, null, indent ? 2 : undefined)})`;
    }
    toJSON() {
        return JSON.stringify(Array.from(this.getInner()));
    }
    static fromJSON(json) {
        return new MultiSet(JSON.parse(json));
    }
    /**
     * Apply a function to all records in the collection.
     */
    map(f) {
        return new MultiSet(this.#inner.map(([data, multiplicity]) => [f(data), multiplicity]));
    }
    /**
     * Filter out records for which a function f(record) evaluates to False.
     */
    filter(f) {
        return new MultiSet(this.#inner.filter(([data, _]) => f(data)));
    }
    /**
     * Negate all multiplicities in the collection.
     */
    negate() {
        return new MultiSet(this.#inner.map(([data, multiplicity]) => [data, -multiplicity]));
    }
    /**
     * Concatenate two collections together.
     */
    concat(other) {
        const out = [];
        chunkedArrayPush(out, this.#inner);
        chunkedArrayPush(out, other.getInner());
        return new MultiSet(out);
    }
    /**
     * Produce as output a collection that is logically equivalent to the input
     * but which combines identical instances of the same record into one
     * (record, multiplicity) pair.
     */
    consolidate() {
        const consolidated = new DefaultMap(() => 0);
        const values = new Map();
        let hasString = false;
        let hasNumber = false;
        let hasOther = false;
        for (const [data, _] of this.#inner) {
            if (typeof data === 'string') {
                hasString = true;
            }
            else if (typeof data === 'number') {
                hasNumber = true;
            }
            else {
                hasOther = true;
                break;
            }
        }
        const requireJson = hasOther || (hasString && hasNumber);
        for (const [data, multiplicity] of this.#inner) {
            const key = requireJson ? hash(data) : data;
            if (requireJson && !values.has(key)) {
                values.set(key, data);
            }
            consolidated.update(key, (count) => count + multiplicity);
        }
        const result = [];
        for (const [key, multiplicity] of consolidated.entries()) {
            if (multiplicity !== 0) {
                const parsedKey = requireJson ? values.get(key) : key;
                result.push([parsedKey, multiplicity]);
            }
        }
        return new MultiSet(result);
    }
    extend(other) {
        const otherArray = other instanceof MultiSet ? other.getInner() : other;
        chunkedArrayPush(this.#inner, otherArray);
    }
    getInner() {
        return this.#inner;
    }
}
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