57 lines
2.2 KiB
TypeScript
57 lines
2.2 KiB
TypeScript
// License: LGPL-3.0-or-later
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// from https://github.com/mtraynham/lodash-joins/blob/c252b462981562451d85d1e09c8f273ce7fe06c5/lib/hash/hashLeftOuterJoin.ts
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import filter from 'lodash/filter';
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import flatten from 'lodash/flatten';
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import groupBy from 'lodash/groupBy';
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import has from 'lodash/has';
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import map from 'lodash/map';
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import reduceRight from 'lodash/reduceRight';
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import values from 'lodash/values';
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import {Accessor, Merger} from '../typings';
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import {toStringAccessor} from './util';
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/**
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* Hash left outer join
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*/
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export default function hashLeftOuterJoin<LeftRow, RightRow, Key, MergeResult>(
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a: LeftRow[],
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aAccessor: Accessor<LeftRow, Key>,
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b: RightRow[],
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bAccessor: Accessor<RightRow, Key>,
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merger: Merger<LeftRow, RightRow | undefined, MergeResult>
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): MergeResult[] {
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if (a.length < 1 || b.length < 1) {
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return map(a, (a: LeftRow) => merger(a, undefined));
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}
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const leftAccessor: Accessor<LeftRow, string> = toStringAccessor(aAccessor),
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rightAccessor: Accessor<RightRow, string> = toStringAccessor(bAccessor);
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let index: {[key: string]: (LeftRow | RightRow)[]},
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key: string;
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if (a.length < b.length) {
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const seen: {[key: string]: boolean} = {};
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index = groupBy(a, leftAccessor);
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return reduceRight(b, (previous: MergeResult[], bDatum: RightRow) => {
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seen[key = rightAccessor(bDatum)] = true;
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if (has(index, key)) {
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return map(index[key], (aDatum: LeftRow) => merger(aDatum, bDatum)).concat(previous);
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}
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return previous;
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}, []).concat(
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map(
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flatten(values(filter(
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index,
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(val: (LeftRow | RightRow)[], key: string) =>
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!has(seen, key)))),
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(aDatum: LeftRow) => merger(aDatum, undefined)));
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}
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index = groupBy(b, rightAccessor);
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return reduceRight(a, (previous: MergeResult[], aDatum: LeftRow) => {
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key = leftAccessor(aDatum);
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if (has(index, key)) {
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return map(index[key], (bDatum: RightRow) => merger(aDatum, bDatum)).concat(previous);
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}
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previous.unshift(merger(aDatum, undefined));
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return previous;
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}, []);
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}
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