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Generate Test Data

This tutorial describes how to quickly generate test data as needed to test basic MongoDB operations.

Insert Multiple Documents Using a For Loop

1

Insert new documents into the testData collection.

From the mongo shell, use the for loop. If the testData collection does not exist, MongoDB will implicitly create the collection.

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for (var i = 1; i <= 25; i++) {
   db.testData.insert( { x : i } )
}

2

Query the collection.

Use find() to query the collection:

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db.testData.find()

The mongo shell displays the first 20 documents in the collection. Your ObjectId values will be different:

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{ "_id" : ObjectId("53d7be30242b692a1138ac7d"), "x" : 1 }
{ "_id" : ObjectId("53d7be30242b692a1138ac7e"), "x" : 2 }
{ "_id" : ObjectId("53d7be30242b692a1138ac7f"), "x" : 3 }
{ "_id" : ObjectId("53d7be30242b692a1138ac80"), "x" : 4 }
{ "_id" : ObjectId("53d7be30242b692a1138ac81"), "x" : 5 }
{ "_id" : ObjectId("53d7be30242b692a1138ac82"), "x" : 6 }
{ "_id" : ObjectId("53d7be30242b692a1138ac83"), "x" : 7 }
{ "_id" : ObjectId("53d7be30242b692a1138ac84"), "x" : 8 }
{ "_id" : ObjectId("53d7be30242b692a1138ac85"), "x" : 9 }
{ "_id" : ObjectId("53d7be30242b692a1138ac86"), "x" : 10 }
{ "_id" : ObjectId("53d7be30242b692a1138ac87"), "x" : 11 }
{ "_id" : ObjectId("53d7be30242b692a1138ac88"), "x" : 12 }
{ "_id" : ObjectId("53d7be30242b692a1138ac89"), "x" : 13 }
{ "_id" : ObjectId("53d7be30242b692a1138ac8a"), "x" : 14 }
{ "_id" : ObjectId("53d7be30242b692a1138ac8b"), "x" : 15 }
{ "_id" : ObjectId("53d7be30242b692a1138ac8c"), "x" : 16 }
{ "_id" : ObjectId("53d7be30242b692a1138ac8d"), "x" : 17 }
{ "_id" : ObjectId("53d7be30242b692a1138ac8e"), "x" : 18 }
{ "_id" : ObjectId("53d7be30242b692a1138ac8f"), "x" : 19 }
{ "_id" : ObjectId("53d7be30242b692a1138ac90"), "x" : 20 }
Type "it" for more

3

Iterate through the cursor.

The find() method returns a cursor. To iterate the cursor and return more documents, type it in the mongo shell. The shell will exhaust the cursor and return these documents:

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{ "_id" : ObjectId("53d7be30242b692a1138ac91"), "x" : 21 }
{ "_id" : ObjectId("53d7be30242b692a1138ac92"), "x" : 22 }
{ "_id" : ObjectId("53d7be30242b692a1138ac93"), "x" : 23 }
{ "_id" : ObjectId("53d7be30242b692a1138ac94"), "x" : 24 }
{ "_id" : ObjectId("53d7be30242b692a1138ac95"), "x" : 25 }

Insert Multiple Documents with a mongo Shell Function

You can create a JavaScript function in your shell session to generate the above data. The insertData() JavaScript function that follows creates new data for use in testing or training by either creating a new collection or appending data to an existing collection:

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function insertData(dbName, colName, num) {

  var col = db.getSiblingDB(dbName).getCollection(colName);

  for (i = 0; i < num; i++) {
    col.insert({x:i});
  }

  print(col.count());

}

The insertData() function takes three parameters: a database, a new or existing collection, and the number of documents to create. The function creates documents with an x field set to an incremented integer, as in the following example documents:

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{ "_id" : ObjectId("51a4da9b292904caffcff6eb"), "x" : 0 }
{ "_id" : ObjectId("51a4da9b292904caffcff6ec"), "x" : 1 }
{ "_id" : ObjectId("51a4da9b292904caffcff6ed"), "x" : 2 }

Store the function in your .mongorc.js file. The mongo shell loads and parses the .mongorc.js file on startup so your function is available every time you start a session.

Example

Specify database name, collection name, and the number of documents to insert as arguments to insertData().

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insertData("test", "testData", 400)

This operation inserts 400 documents into the testData collection in the test database. If the collection and database do not exist, MongoDB creates them implicitly before inserting documents.

Additional Resources

• Python utils to create random JSON data and import into mongoDB

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