The driver is a package for interacting with . node.js MongoDB Importing a JSON The command allows us to import human readable in a specific database & a collection. To import a data in a specific & a collection, type mongoimport JSON JSON database mongoimport -d databaseName -c collectionName jsonFileName.json find() and Cursors in the Node.js Driver var MongoClient = require('mongodb').MongoClient,assert = require('assert'); MongoClient.connect('mongodb://localhost:27017/crunchbase', function(err, db) { assert.equal(err, null);console.log("Successfully connected to MongoDB."); var query = {"category_code": "biotech"}; db.collection('companies').find(query).toArray(function(err, docs) { assert.equal(err, null);assert.notEqual(docs.length, 0); docs.forEach(function(doc) {console.log(doc.name + " is a " + doc.category_code + " company.");}); db.close(); }); }); Notice that the call is making the application to fetch the entire dataset. .toArray var MongoClient = require('mongodb').MongoClient,assert = require('assert'); MongoClient.connect('mongodb://localhost:27017/crunchbase', function(err, db) { assert.equal(err, null);console.log("Successfully connected to MongoDB."); var query = {"category_code": "biotech"}; var cursor = db.collection('companies').find(query); function(doc) {cursor.forEach(console.log( doc.name + " is a " + doc.category_code + " company." );},function(err) {assert.equal(err, null);return db.close();});}); Notice that the returned by the is assigned to . With this approach, instead of fetching all data in memort and consuming data at once, we’re streaming the data to our application. can create a cursor immediately because it doesn’t actually make a request to the database until we try to use some of the documents it will provide. The point of is to describe our query. The 2nd parameter to shows what to do when the driver gets exhausted or an error occurs. cursor find() var cursor find() cursor cursor.forEach In the initial version of the above code, it was which forced the database call. It meant we needed the documents and wanted them to be in an . toArray() ALL array Also, returns data in batch . The image below shows, requests from cursors (from application) to MongoDB format MongoDB is better than because we can process documents until we reach the end. Contrast it with - where we wait for the documents to be retrieved and the array is built. This means we’re not getting any advantage from the fact that the driver and the database system are working together to batch results to your application. Batching is meant to provide efficiency in terms of memory overhead and the execution time. . forEach toArray as they come in toArray ALL entire Take advantage of it, if you can in your application Projection in the Node.js Driver Remember that projections allows us to explicitly include or exclude fields in a query. We use to indicate that we want to include a field and to indicate that we wish to exclude the field. Remember that field is special - MongoDB **1** **0** _id field gets included by default, unless we explicitly exclude it _id All other fields are excluded, until we explicitly include them Also, since we’re working in , we can construct our project documents and documents to be inserted into our collections in a way that is very similar to the way we do this in the shell. What’s different is the driver provides one set of classes and methods we use to interact with and the shell provides it’s own API. javascript mongo MongoDB mongo W. r. t. as of the driver and the shell adhere to the same spec. How you access these methods and how they’re implemented varies of course, from the shell. CRUD MongoDB 3.2 mongo mongo var MongoClient = require('mongodb').MongoClient,assert = require('assert'); MongoClient.connect('mongodb://localhost:27017/crunchbase', function(err, db) { assert.equal(err, null);console.log("Successfully connected to MongoDB."); var query = {"category_code": "biotech"};var projection = {"name": 1, "category_code": 1, "_id": 0}; var cursor = db.collection('companies').find(query);cursor.project(projection); cursor.forEach(function(doc) {console.log(doc.name + " is a " + doc.category_code + " company.");console.log(doc);},function(err) {assert.equal(err, null);return db.close();}); }); The current best practice in the driver, is to chain a call to onto our i.e. . This call to project sets a field projection for the query. This call does not force a request to retrieve documents from the database, as does the method. Rather it adds some additional details to the query representation maintained by our . There’re a number of cursor methods, we can chain together to fully express the operation we wish to execute against our database. The call to is synchronous. We’re going to modify that with a field here using the method on the cursor. node.js project cursor cursor.project foreach cursor MongoDB db.collection cursor projection project Query Operators in the Node.js Driver var MongoClient = require('mongodb').MongoClient,commandLineArgs = require('command-line-args'),assert = require('assert'); var options = commandLineOptions(); MongoClient.connect('mongodb://localhost:27017/crunchbase', function(err, db) { assert.equal(err, null);console.log("Successfully connected to MongoDB."); var query = queryDocument(options);var projection = {"_id": 1, "name": 1, "founded_year": 1,"number_of_employees": 1, "crunchbase_url": 1}; var cursor = db.collection('companies').find(query, projection);var numMatches = 0; cursor.forEach(function(doc) {numMatches = numMatches + 1;console.log( doc );},function(err) {assert.equal(err, null);console.log("Our query was:" + JSON.stringify(query));console.log("Matching documents: " + numMatches);return db.close();}); }); function queryDocument(options) { console.log(options); var query = {"founded_year": {"$gte": options.firstYear,"$lte": options.lastYear}}; if ("employees" in options) {query.number_of_employees = { "$gte": options.employees };} return query; } function commandLineOptions() { var cli = commandLineArgs([{ name: "firstYear", alias: "f", type: Number },{ name: "lastYear", alias: "l", type: Number },{ name: "employees", alias: "e", type: Number }]); var options = cli.parse()if ( !(("firstYear" in options) && ("lastYear" in options))) {console.log(cli.getUsage({title: "Usage",description: "The first two options below are required. The rest are optional."}));process.exit();} return options; } To call it use . Notice that is getting d. Also, you might see the difference between the field representation by shell and driver: node app.js -f 2004 -l 2008 -e 100 commandLineArgs parse _id mongo node.js on shell _id : ObjectId("507f1f77bcf86cd799439011") mongo on driver _id : 507f1f77bcf86cd799439011 node.js This happens because of the difference in the way driver and the shell chooses to stringify the field. node.js mongo _id $regex in the Node.js Driver var MongoClient = require('mongodb').MongoClient,commandLineArgs = require('command-line-args'),assert = require('assert'); var options = commandLineOptions(); MongoClient.connect('mongodb://localhost:27017/crunchbase', function(err, db) { assert.equal(err, null);console.log("Successfully connected to MongoDB."); var query = queryDocument(options);var projection = projectionDocument(options); var cursor = db.collection('companies').find(query);cursor.project(projection); var numMatches = 0; cursor.forEach(function(doc) {numMatches = numMatches + 1;console.log( doc );},function(err) {assert.equal(err, null);console.log("Our query was:" + JSON.stringify(query));console.log("Matching documents: " + numMatches);return db.close();}); }); function queryDocument(options) { console.log(options); var query = {}; if ("overview" in options) {query.overview = {"$regex": options.overview, "$options": "i"};} if ("milestones" in options) {query["milestones.source_description"] ={"$regex": options.milestones, "$options": "i"};} return query;} function projectionDocument(options) { var projection = {"_id": 0,"name": 1,"founded_year": 1}; if ("overview" in options) {projection.overview = 1;} if ("milestones" in options) {projection["milestones.source_description"] = 1;} return projection;} function commandLineOptions() { var cli = commandLineArgs([{ name: "overview", alias: "o", type: String },{ name: "milestones", alias: "m", type: String }]); var options = cli.parse()if (Object.keys(options).length < 1) {console.log(cli.getUsage({title: "Usage",description: "You must supply at least one option. See below."}));process.exit();} return options;} The set to indicates that the search needs to be case-insensitive. supports like regular expressions. There’re a couple of ways in which we can set the values for the query documents: $options i regex MongoDB perl Using curly braces { "_id": 0, "name": 1, "founded_year": 1 } Using dots projection.overview = 1; Using array indexing projection["milestones.source_description"] = 1; Sort, Skip, and Limit in the Node.js Driver To sort documents, we can apply on a object. To enforce order of sort, instead of passing an object, we need to pass an array to the method. sort cursor sort var MongoClient = require('mongodb').MongoClient,commandLineArgs = require('command-line-args'),assert = require('assert'); var options = commandLineOptions(); MongoClient.connect('mongodb://localhost:27017/crunchbase', function(err, db) { assert.equal(err, null);console.log("Successfully connected to MongoDB."); var query = queryDocument(options);var projection = {"_id": 0,"name": 1,"founded_year": 1,"number_of_employees": 1}; var cursor = db.collection('companies').find(query);cursor.project(projection);cursor.limit(options.limit);cursor.skip(options.skip);cursor.sort([["founded_year", 1],["number_of_employees", -1]]); var numMatches = 0; cursor.forEach(function(doc) {numMatches = numMatches + 1;console.log(doc.name + "\n\tfounded " + doc.founded_year +"\n\t" + doc.number_of_employees + " employees");},function(err) {assert.equal(err, null);console.log("Our query was:" + JSON.stringify(query));console.log("Documents displayed: " + numMatches);return db.close();}); }); function queryDocument(options) { console.log(options); var query = {"founded_year": {"$gte": options.firstYear,"$lte": options.lastYear}}; if ("employees" in options) {query.number_of_employees = {"$gte": options.employees};} return query; } function commandLineOptions() { var cli = commandLineArgs([{name: "firstYear",alias: "f",type: Number}, {name: "lastYear",alias: "l",type: Number}, {name: "employees",alias: "e",type: Number}, {name: "skip",type: Number,defaultValue: 0}, {name: "limit",type: Number,defaultValue: 20000}]); var options = cli.parse()if (!(("firstYear" in options) && ("lastYear" in options))) {console.log(cli.getUsage({title: "Usage",description: "The first two options below are required. The rest are optional."}));process.exit();} return options; } One thing to notice is the order in which applies , and MongoDB skip limit sort There’s also a possibility that we can sort data on the side as well, provided that we’ve setup the indexing. MongoDB Notice that driver will send a query when we call a cursor method passing a callback function to process query results. MongoDB Photos Originally published at xameeramir.github.io .

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