25 lines
870 B
TypeScript
25 lines
870 B
TypeScript
// License: LGPL-3.0-or-later
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// from https://github.com/mtraynham/lodash-joins/blob/c252b462981562451d85d1e09c8f273ce7fe06c5/lib/hash/hashLeftSemiJoin.ts
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import filter from 'lodash/filter';
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import has from 'lodash/has';
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import keyBy from 'lodash/keyBy';
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import {Accessor} from '../typings';
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import {toStringAccessor} from './util';
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/**
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* Hash left semi join
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*/
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export default function hashLeftSemiJoin<LeftRow, RightRow, Key>(
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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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): LeftRow[] {
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if (a.length < 1 || b.length < 1) {
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return [];
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}
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const index: {[key: string]: RightRow} = keyBy(b, toStringAccessor(bAccessor)),
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leftAccessor: Accessor<LeftRow, string> = toStringAccessor(aAccessor);
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return filter(a, (aDatum: LeftRow) => has(index, leftAccessor(aDatum)));
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}
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