eav.js

let counter = 1;

const db = [];
const entityIndex = new Map();
const valueIndex = new Map();
const attributeIndex = new Map();

const add = (obj) => {
  const op = true;
  const tx = new Date().getTime();
  const entity = counter++;
  entityIndex.set(entity, new Set());

  const keys = Object.keys(obj);
  let idx = 0;
  while (idx < keys.length) {
    const attribute = keys[idx];
    const value = obj[attribute];

    if (value) {
      const row = [entity, attribute, value, tx, op];
      const length = db.push(row);
      const dbLocation = length - 1;
      entityIndex.get(entity).add(dbLocation);
      if (!attributeIndex.has(attribute)) {
        attributeIndex.set(attribute, new Set());
      }
      if (!valueIndex.has(value)) {
        valueIndex.set(value, new Set());
      }
      entityIndex.get(entity).add(dbLocation);
      attributeIndex.get(attribute).add(dbLocation);
      valueIndex.get(value).add(dbLocation);
    }
    idx++;
  }
};

const isVar = RegExp(/^\?/);
const isWildcard = RegExp(/^_$/);
const intersection = (a, b) => new Set([...a].filter((x) => b.has(x)));
const setToRows = (set) => [...set].map((idx) => db[idx]);
const isSubset = (a, b) => [...a].filter((x) => b.has(x)) === 0;
const merge = (a) => (b) => new Map([...a, ...b]);
const joinable = (keys) => (a) => (b) =>
  [...keys].every((key) => a.get(key) === b.get(key));

const applyRule = (rule) => {
  const [e, a, v] = rule;
  const map = rule.reduce(
    (acc, value, index) => (isVar.test(value) ? acc.set(index, value) : acc),
    new Map()
  );
  const sets = [];
  if (!isVar.test(e) && !isWildcard.test(e)) {
    sets.push(entityIndex.get(e) || new Set());
  }
  if (!isVar.test(a) && !isWildcard.test(a)) {
    sets.push(attributeIndex.get(a) || new Set());
  }
  if (!isVar.test(v) && !isWildcard.test(v)) {
    sets.push(valueIndex.get(v) || new Set());
  }
  const rows = setToRows(sets.reduce(intersection)).map((row) => {
    return [...map].reduce((match, [key, value]) => {
      return match.set(value, row[key]);
    }, new Map());
  });
  const vars = new Set(rule.filter((x) => isVar.test(x)));
  return { rows, vars };
};

const join = (a, b) => {
  const keys = intersection(a.vars, b.vars);
  const match = keys.size > 0 ? joinable(keys) : () => () => true;
  const vars = new Set([...a.vars, ...b.vars]);
  const rows = a.rows.flatMap((row) => {
    return b.rows.filter(match(row)).map(merge(row));
  });
  return { vars, rows };
};
const data = [
  {
    shelf: "javascript",
    isbn: "9781449331818",
  },
  {
    isbn: "9781449325862",
    shelf: "git",
  },
  {
    shelf: "javascript",
    isbn: "9781593275846",
  },
  {
    isbn: "9781593275846",
    title: "Eloquent JavaScript, Second Edition",
    subtitle: "A Modern Introduction to Programming",
    author: "Marijn Haverbeke",
    published: "2014-12-14T00:00:00.000Z",
    publisher: "No Starch Press",
    pages: 472,
  },
  {
    isbn: "9781449331818",
    title: "Learning JavaScript Design Patterns",
    subtitle: "A JavaScript and jQuery Developer's Guide",
    author: "Addy Osmani",
    published: "2012-07-01T00:00:00.000Z",
    publisher: "O'Reilly Media",
    pages: 254,
  },
  {
    isbn: "9781449365035",
    title: "Speaking JavaScript",
    subtitle: "An In-Depth Guide for Programmers",
    author: "Axel Rauschmayer",
    published: "2014-02-01T00:00:00.000Z",
    publisher: "O'Reilly Media",
    pages: 460,
  },
  {
    isbn: "9781491950296",
    title: "Programming JavaScript Applications",
    subtitle:
      "Robust Web Architecture with Node, HTML5, and Modern JS Libraries",
    author: "Eric Elliott",
    published: "2014-07-01T00:00:00.000Z",
    publisher: "O'Reilly Media",
    pages: 254,
  },
  {
    isbn: "9781593277574",
    title: "Understanding ECMAScript 6",
    subtitle: "The Definitive Guide for JavaScript Developers",
    author: "Nicholas C. Zakas",
    published: "2016-09-03T00:00:00.000Z",
    publisher: "No Starch Press",
    pages: 352,
  },
  {
    isbn: "9781491904244",
    title: "You Don't Know JS",
    subtitle: "ES6 & Beyond",
    author: "Kyle Simpson",
    published: "2015-12-27T00:00:00.000Z",
    publisher: "O'Reilly Media",
    pages: 278,
  },
  {
    isbn: "9781449325862",
    title: "Git Pocket Guide",
    subtitle: "A Working Introduction",
    author: "Richard E. Silverman",
    published: "2013-08-02T00:00:00.000Z",
    publisher: "O'Reilly Media",
    pages: 234,
  },
  {
    isbn: "9781449337711",
    title: "Designing Evolvable Web APIs with ASP.NET",
    subtitle: "Harnessing the Power of the Web",
    author: "Glenn Block, et al.",
    published: "2014-04-07T00:00:00.000Z",
    publisher: "O'Reilly Media",
    pages: 538,
  },
];

data.forEach(add);

const rules = [
  ["?book", "publisher", "O'Reilly Media"],
  ["?book", "author", "?author"],
  ["?book", "isbn", "?isbn"],
  ["?shelf", "shelf", "git"],
  ["?shelf", "isbn", "?isbn"]
];

rules.map(applyRule).reduce(join);