@electric-sql/d2mini/dist/operators/distinct.js

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

import { DifferenceStreamWriter } from '../graph.js';
import { StreamBuilder } from '../d2.js';
import { ReduceOperator } from './reduce.js';
import { hash } from '../utils.js';
/**
 * Operator that removes duplicates by key (version-free)
 */
export class DistinctOperator extends ReduceOperator {
    constructor(id, inputA, output) {
        const distinctInner = (vals) => {
            const consolidated = new Map();
            const values = new Map();
            for (const [val, diff] of vals) {
                const key = hash(val);
                consolidated.set(key, (consolidated.get(key) || 0) + diff);
                values.set(key, val);
            }
            return Array.from(consolidated.entries())
                .filter(([_, count]) => count > 0)
                .map(([key, _]) => [values.get(key), 1]);
        };
        super(id, inputA, output, distinctInner);
    }
}
/**
 * Removes duplicates by key (version-free)
 */
export function distinct() {
    return (stream) => {
        const output = new StreamBuilder(stream.graph, new DifferenceStreamWriter());
        const operator = new DistinctOperator(stream.graph.getNextOperatorId(), stream.connectReader(), output.writer);
        stream.graph.addOperator(operator);
        stream.graph.addStream(output.connectReader());
        return output;
    };
}
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