Category: Nodejs

Node.js is a popular runtime platform to create programs that run on it.

It lets us run JavaScript outside the browser.

In this article, we’ll look at how to start using Node.js to create programs.

Text Indexes

Text indexes let us do text searches on queries that have string content.

It can include any field whose value is a string or an array of strings.

For example, we can create the index and use it by wriing”

const { MongoClient } = require('mongodb');
const connection = "mongodb://localhost:27017";
const client = new MongoClient(connection);

async function run() {
  try {
    await client.connect();
    const db = client.db("test");
    const testCollection = await db.collection('test');
    await testCollection.dropIndexes();
    const indexResult = await testCollection.createIndex({ name: "text" }, { default_language: "english" });
    console.log(indexResult)
    await testCollection.deleteMany({})
    const result = await testCollection.insertMany([
      { "_id": 1, "name": "apples", "qty": 5, "rating": 3 },
      { "_id": 2, "name": "bananas", "qty": 7, "rating": 1 },
      { "_id": 3, "name": "oranges", "qty": 6, "rating": 2 },
      { "_id": 4, "name": "avocados", "qty": 3, "rating": 5 },
    ]);
    console.log(result)
    const query = { $text: { $search: "apple" } };
    const projection = { name: 1 };
    const cursor = testCollection
      .find(query)
      .project(projection);
    cursor.forEach(console.dir);
  } finally {
    await client.close();
  }
}
run().catch(console.dir);

We create the index by writing:

const indexResult = await testCollection.createIndex({ name: "text" }, { default_language: "english" });

The createIndex method adds the index to the name field.

The 2nd argument has the options for creating the index.

The default_language sets the index language.

Unique Indexes

We can add a unique index that index fields that don’t store duplicate values.

The _id field has a unique index added to it when the collection is created.

For example, we can write:

const { MongoClient } = require('mongodb');
const connection = "mongodb://localhost:27017";
const client = new MongoClient(connection);

async function run() {
  try {
    await client.connect();
    const db = client.db("test");
    const testCollection = await db.collection('test');
    await testCollection.dropIndexes();
    const indexResult = await testCollection.createIndex({ name: "text" }, { unique: true });
    console.log(indexResult)
    await testCollection.deleteMany({})
    const result = await testCollection.insertMany([
      { "_id": 1, "name": "apples", "qty": 5, "rating": 3 },
      { "_id": 2, "name": "bananas", "qty": 7, "rating": 1 },
      { "_id": 3, "name": "oranges", "qty": 6, "rating": 2 },
      { "_id": 4, "name": "avocados", "qty": 3, "rating": 5 },
    ]);
    console.log(result)
    const query = {};
    const projection { name: 1 };
    const cursor = testCollection
      .find(query)
      .project(projection);
    cursor.forEach(console.dir);
  } finally {
    await client.close();
  }
}
run().catch(console.dir);

to call createIndex with the 2nd argument being an object with the unique property set to true .

If there’re any duplicate values in the field in the collection, then we get the ‘duplicate key error index’ error when we try to create the index.

Conclusion

We can add indexes for text searches and indexing unique values for MongoDB fields.

Node.js is a popular runtime platform to create programs that run on it.

It lets us run JavaScript outside the browser.

In this article, we’ll look at how to start using Node.js to create programs.

Promises and Callbacks

The MongoDB client has methods that return promises.

They’re async code that can have the status pending before it has the result.

Once it has a result, the it can be fulfilled if the operation is done successfully.

Otherwise, it has the rejected status.

For example, the updateOne method returns a promise.

We can use it by writing:

const { MongoClient } = require('mongodb');
const connection = "mongodb://localhost:27017";
const client = new MongoClient(connection);

async function run() {
  try {
    await client.connect();
    const testCollection = await client.db("test").collection('test');
    await testCollection.deleteMany({})
    const result = await testCollection.insertMany([
      { "_id": 1, "name": "apples", "qty": 5, "rating": 3 },
      { "_id": 2, "name": "bananas", "qty": 7, "rating": 1 },
      { "_id": 3, "name": "oranges", "qty": 6, "rating": 2 },
      { "_id": 4, "name": "avocados", "qty": 3, "rating": 5 },
    ]);
    console.log(result)
    const updateResult = await testCollection
      .updateOne({ name: "apple" }, { $set: { qty: 100 } })
    console.log(updateResult);
  } finally {
    await client.close();
  }
}
run().catch(console.dir);

We call updateOne with the await keyword so that we can get the resolved value once we have it.

updateOne returns a promise, so we can use the await keyword.

If we want to catch errors, then we can write:

const { MongoClient } = require('mongodb');
const connection = "mongodb://localhost:27017";
const client = new MongoClient(connection);

async function run() {
  try {
    await client.connect();
    const testCollection = await client.db("test").collection('test');
    await testCollection.deleteMany({})
    const result = await testCollection.insertMany([
      { "_id": 1, "name": "apples", "qty": 5, "rating": 3 },
      { "_id": 2, "name": "bananas", "qty": 7, "rating": 1 },
      { "_id": 3, "name": "oranges", "qty": 6, "rating": 2 },
      { "_id": 4, "name": "avocados", "qty": 3, "rating": 5 },
    ]);
    console.log(result)
    try {
      const updateResult = await testCollection
        .updateOne({ name: "apple" }, { $set: { qty: 100 } })
      console.log(updateResult);
    } catch (error) {
      console.log(`Updated ${res.result.n} documents`)
    }

} finally {
    await client.close();
  }
}
run().catch(console.dir);

to add a catch block to log any errors that’s raised from the rejected promise.

Callbacks

We can also use callbacks to get the result of an operation.

For example, we can write:

const { MongoClient } = require('mongodb');
const connection = "mongodb://localhost:27017";
const client = new MongoClient(connection);

async function run() {
  try {
    await client.connect();
    const testCollection = await client.db("test").collection('test');
    await testCollection.deleteMany({})
    const result = await testCollection.insertMany([
      { "_id": 1, "name": "apples", "qty": 5, "rating": 3 },
      { "_id": 2, "name": "bananas", "qty": 7, "rating": 1 },
      { "_id": 3, "name": "oranges", "qty": 6, "rating": 2 },
      { "_id": 4, "name": "avocados", "qty": 3, "rating": 5 },
    ]);
    console.log(result)
    testCollection
      .updateOne({ name: "apple" }, { $set: { qty: 100 } }, (error, result) => {
        if (!error) {
          console.log(`Operation completed successfully`);
        } else {
          console.log(`An error occurred: ${error}`);
        }
      })
  } finally {
    await client.close();
  }
}
run().catch(console.dir);

We call updateOne with a callback in the 3rd argument.

This lets us get the async result with the callback instead of returning a promise.

Conclusion

The MongoDB client returns promises or we can use callbacks to get the result from an async operation.

Node.js is a popular runtime platform to create programs that run on it.

It lets us run JavaScript outside the browser.

In this article, we’ll look at how to start using Node.js to create programs.

Index Types

MongoDB has different text types.

We can add single field indexes to improve performance for queries that specify ascending or descending sort order on a single field of a document.

For example, we can write:

const { MongoClient } = require('mongodb');
const connection = "mongodb://localhost:27017";
const client = new MongoClient(connection);

async function run() {
  try {
    await client.connect();
    const db = client.db("test");
    const testCollection = await db.collection('test');
    await testCollection.dropIndexes();
    const indexResult = await testCollection.createIndex({ name: 1 });
    console.log(indexResult)
    await testCollection.deleteMany({})
    const result = await testCollection.insertMany([
      { "_id": 1, "name": "apples", "qty": 5, "rating": 3 },
      { "_id": 2, "name": "bananas", "qty": 7, "rating": 1 },
      { "_id": 3, "name": "oranges", "qty": 6, "rating": 2 },
      { "_id": 4, "name": "avocados", "qty": 3, "rating": 5 },
    ]);
    console.log(result)
    const query = {};
    const sort = { name: 1 };
    const cursor = testCollection
      .find(query)
      .sort(sort);
    cursor.forEach(console.dir);
  } finally {
    await client.close();
  }
}
run().catch(console.dir);

We call the sort method with the object with the sort order.

Compound index ae indexes that improve performance for queries that specify ascending or descending sort order for multiple fields in a document.

For example, we can add a compound for the name and rating fields and use it by writing:

const { MongoClient } = require('mongodb');
const connection = "mongodb://localhost:27017";
const client = new MongoClient(connection);

async function run() {
  try {
    await client.connect();
    const db = client.db("test");
    const testCollection = await db.collection('test');
    await testCollection.dropIndexes();
    const indexResult = await testCollection.createIndex({ name: 1, rating: 1 });
    console.log(indexResult)
    await testCollection.deleteMany({})
    const result = await testCollection.insertMany([
      { "_id": 1, "name": "apples", "qty": 5, "rating": 3 },
      { "_id": 2, "name": "bananas", "qty": 7, "rating": 1 },
      { "_id": 3, "name": "oranges", "qty": 6, "rating": 2 },
      { "_id": 4, "name": "avocados", "qty": 3, "rating": 5 },
    ]);
    console.log(result)
    const query = {};
    const sort = { name: 1, rating: 1 };
    const cursor = testCollection
      .find(query)
      .sort(sort);
    cursor.forEach(console.dir);
  } finally {
    await client.close();
  }
}
run().catch(console.dir);

We have:

const indexResult = await testCollection.createIndex({ name: 1, rating: 1 });

to add the compound index.

Then we call sort with an object that has both the name and rating fields.

Multikey indexes are indexes that improve performance on queries that specifies ascending or descending index on fields that has an array value.

For example, we can create a multikey index and use it by writing:

const { MongoClient } = require('mongodb');
const connection = "mongodb://localhost:27017";
const client = new MongoClient(connection);

async function run() {
  try {
    await client.connect();
    const db = client.db("test");
    const testCollection = await db.collection('test');
    await testCollection.dropIndexes();
    const indexResult = await testCollection.createIndex({ types: 1 });
    console.log(indexResult)
    await testCollection.deleteMany({})
    const result = await testCollection.insertMany([
      { "_id": 1, "name": "apples", "qty": 5, "rating": 3, "types": ["granny smith", "mcintosh"] },
      { "_id": 2, "name": "bananas", "qty": 7, "rating": 1, "types": ["chiquita", "del monte"] },
      { "_id": 3, "name": "oranges", "qty": 6, "rating": 2, "types": [] },
      { "_id": 4, "name": "avocados", "qty": 3, "rating": 5, "types": [] },
    ]);
    console.log(result)
    const query = { types: "granny smith" };
    const sort = { types: 1 };
    const projection = { types: 1 };
    const cursor = testCollection
      .find(query)
      .sort(sort)
      .project(projection);
    cursor.forEach(console.dir);
  } finally {
    await client.close();
  }
}
run().catch(console.dir);

We have:

const indexResult = await testCollection.createIndex({ types: 1 });

to create the index on the types field.

Then we can make the query on the types field.

Conclusion

MongoDB has various types of indexes to optimize the performance of various kinds of queries.

Node.js is a popular runtime platform to create programs that run on it.

It lets us run JavaScript outside the browser.

In this article, we’ll look at how to start using Node.js to create programs.

Creating Indexes

We can create indexes in our collection to let us enable searches in the collection.

For example, we can write:

const { MongoClient } = require('mongodb');
const connection = "mongodb://localhost:27017";
const client = new MongoClient(connection);

async function run() {
  try {
    await client.connect();
    const db = client.db("test");
    const testCollection = await db.collection('test');
    const indexResult = await testCollection.createIndex({ name: 1 });
    console.log(indexResult)
    await testCollection.deleteMany({})
    const result = await testCollection.insertMany([
      { "_id": 1, "name": "apples", "qty": 5, "rating": 3 },
      { "_id": 2, "name": "bananas", "qty": 7, "rating": 1 },
      { "_id": 3, "name": "oranges", "qty": 6, "rating": 2 },
      { "_id": 4, "name": "avocados", "qty": 3, "rating": 5 },
    ]);
    console.log(result)
  } finally {
    await client.close();
  }
}
run().catch(console.dir);

We call the createIndex method on the testCollection to add an index to it.

Then we can query the collection by writing:

const { MongoClient } = require('mongodb');
const connection = "mongodb://localhost:27017";
const client = new MongoClient(connection);

async function run() {
  try {
    await client.connect();
    const db = client.db("test");
    const testCollection = await db.collection('test');
    const indexResult = await testCollection.createIndex({ name: 1 });
    console.log(indexResult)
    await testCollection.deleteMany({})
    const result = await testCollection.insertMany([
      { "_id": 1, "name": "apples", "qty": 5, "rating": 3 },
      { "_id": 2, "name": "bananas", "qty": 7, "rating": 1 },
      { "_id": 3, "name": "oranges", "qty": 6, "rating": 2 },
      { "_id": 4, "name": "avocados", "qty": 3, "rating": 5 },
    ]);
    console.log(result)
    const query = { name: "apples" };
    const sort = { name: 1 };
    const projection = { name: 1 };
    const cursor = testCollection
      .find(query)
      .sort(sort)
      .project(projection);
    cursor.forEach(console.dir);
  } finally {
    await client.close();
  }
}
run().catch(console.dir);

We can create a text index by setting the value of the key to index to 'text' when we call createIndex .

For example, we can write:

const { MongoClient } = require('mongodb');
const connection = "mongodb://localhost:27017";
const client = new MongoClient(connection);

async function run() {
  try {
    await client.connect();
    const db = client.db("test");
    const testCollection = await db.collection('test');
    await testCollection.dropIndexes();
    const indexResult = await testCollection.createIndex({ name: 'text' });
    console.log(indexResult)
    await testCollection.deleteMany({})
    const result = await testCollection.insertMany([
      { "_id": 1, "name": "apples", "qty": 5, "rating": 3 },
      { "_id": 2, "name": "bananas", "qty": 7, "rating": 1 },
      { "_id": 3, "name": "oranges", "qty": 6, "rating": 2 },
      { "_id": 4, "name": "avocados", "qty": 3, "rating": 5 },
    ]);
    console.log(result)
    const query = { $text: { $search: "apples" } };
    const projection = { name: 1 };
    const cursor = testCollection
      .find(query)
      .project(projection);
    cursor.forEach(console.dir);
  } finally {
    await client.close();
  }
}
run().catch(console.dir);

We have:

const indexResult = await testCollection.createIndex({ name: 'text' });

to add a text index to the name field.

Then we can write:

const query = { $text: { $search: "apples" } };

to make a text search query and return the result from it.

Conclusion

We can add index to a MongoDB collection with the createIndex method.

To enable text searches, we can add text indexes.

Node.js is a popular runtime platform to create programs that run on it.

It lets us run JavaScript outside the browser.

In this article, we’ll look at how to start using Node.js to create programs.

Limit the Number of Returned Results

We can limit the number of returned results by calling the limit method.

For example, we can write:

const { MongoClient } = require('mongodb');
const connection = "mongodb://localhost:27017";
const client = new MongoClient(connection);

async function run() {
  try {
    await client.connect();
    const testCollection = await client.db("test").collection('test');
    await testCollection.deleteMany({})
    const result = await testCollection.insertMany([
      { "_id": 1, "name": "apples", "qty": 5, "rating": 3 },
      { "_id": 2, "name": "bananas", "qty": 7, "rating": 1 },
      { "_id": 3, "name": "oranges", "qty": 6, "rating": 2 },
      { "_id": 4, "name": "avocados", "qty": 3, "rating": 5 },
    ]);
    console.log(result)
    const query = {};
    const sort = { length: -1 };
    const limit = 3;
    const cursor = testCollection.find(query).sort(sort).limit(limit);
    await cursor.forEach(console.dir);
  } finally {
    await client.close();
  }
}
run().catch(console.dir);

We call the limit method with the limit to set the max number of results to 3.

Also, we can set the properties in the query object.

For example, we can write:

const { MongoClient } = require('mongodb');
const connection = "mongodb://localhost:27017";
const client = new MongoClient(connection);

async function run() {
  try {
    await client.connect();
    const testCollection = await client.db("test").collection('test');
    await testCollection.deleteMany({})
    const result = await testCollection.insertMany([
      { "_id": 1, "name": "apples", "qty": 5, "rating": 3 },
      { "_id": 2, "name": "bananas", "qty": 7, "rating": 1 },
      { "_id": 3, "name": "oranges", "qty": 6, "rating": 2 },
      { "_id": 4, "name": "avocados", "qty": 3, "rating": 5 },
    ]);
    console.log(result)
    const query = {};
    const options = {
      sort: { rating: -1 }, limit: 3
    }
    const cursor = testCollection.find(query, options);
    await cursor.forEach(console.dir);
  } finally {
    await client.close();
  }
}
run().catch(console.dir);

We put the limit property in the options object instead of calling limit to limit the number of results.

We can call the skip method to skip the first number of results.

For example, we can write:

const { MongoClient } = require('mongodb');
const connection = "mongodb://localhost:27017";
const client = new MongoClient(connection);

async function run() {
  try {
    await client.connect();
    const testCollection = await client.db("test").collection('test');
    await testCollection.deleteMany({})
    const result = await testCollection.insertMany([
      { "_id": 1, "name": "apples", "qty": 5, "rating": 3 },
      { "_id": 2, "name": "bananas", "qty": 7, "rating": 1 },
      { "_id": 3, "name": "oranges", "qty": 6, "rating": 2 },
      { "_id": 4, "name": "avocados", "qty": 3, "rating": 5 },
    ]);
    console.log(result)
    const query = {};
    const sort = { length: 1 };
    const limit = 3;
    const skip = 3;
    const cursor = testCollection.find(query).sort(sort).limit(limit).skip(skip);
    await cursor.forEach(console.dir);
  } finally {
    await client.close();
  }
}
run().catch(console.dir);

We use the skip method with the limit method to add pagination for the results.

We skip the amount of results to reach the given page.

And limit sets the max number of results per page.

Conclusion

We can limit the number of results and skip some results with the MongoDB Node.js client.