Hello World MongoDB Create Wildcard Index on Single Field

mongo-wildcard-index-single-field.md

MongoDB Hello World Wildcard Index on Single Field

Reference: https://www.mongodb.com/docs/manual/core/indexes/index-types/index-wildcard/create-wildcard-index-single-field/

Start MongoDB

# in one terminal
docker run -it --rm -p 27017:27017 mongo:7

# first install mongosh
# then in another terminal
mongosh

In Mongosh

db.createCollection("col");
db.col.insertOne({
  idx: {
    name: "ryan",
    height: 999,
    state : "CA"
  },
  person: true,
  car: "Toyota",
  food: "Pizza"
});

db.col.insertOne({
  idx: {
    brand: "anker",
    code: 383812,
    type: "charger"
  },
  price: 44,
  size: 11,
  location: "US"
});

db.col.insertOne({
  idx: {
    owner: "apple",
    device: "mba2022",
    price: 2000
  },
  quantity: 43334,
  weight: 122,
  location: "JPN"
});

db.col.createIndex({
  "idx.$**": 1
});

db.col.find({"idx.brand": "anker"});
db.col.find({"idx.brand": "anker", "idx.type": "charger"});

db.col.insertOne({
  idx: {
    brand: "anker",
    code: 33333,
    type: "stand"
  },
  price: 33,
  size: 44,
  location: "US"
});

db.col.insertOne({
  idx: {
    brand: "sonos",
    code: 444,
    type: "speaker1"
  },
  price: 444,
  size: 112,
  location: "US"
});

db.col.find({"idx.brand": {$in: ["anker", "sonos"]} });

db.col.insertOne({
  idx: {
    brand: "sonos",
    code: 4511,
    type: "stand"
  },
  price: 41,
  size: 12,
  location: "US"
});

db.col.find(
  {"idx.brand": {$in: ["anker", "sonos"]}, "idx.type": "stand"}
);

db.col.find(
  {"idx.brand": "anker", "idx.code": {$gt: 33333}}
);

db.col.insertOne({
  idx: {
    brand: "sonos",
    code: 999,
    type: "bracket",
    families: [233, 111, 555],
    mount: {
      type: "arm",
      vesa: true,
      bolt: {
        size: 34,
        metal: "zinc"
      }
    }
  },
  price: 2,
  size: 3,
  location: "US"
});

db.col.find(
  {"idx.families": {$in: [111]}}
);

db.col.find(
  {"idx.mount.bolt.metal": "zinc"}
);

All of these find() queries are index scans 👍 At this point you can play with MongoDB Compass and use the query explainer for more visual views

Keep in mind of the gotchas: https://www.mongodb.com/docs/manual/core/indexes/index-types/index-wildcard/reference/restrictions/#multi-field-query-predicates

Only 1 predicate can be used in the wildcard search, the rest will be filtered on