Using Cursor and its Methods within MongoDB:
Hope you are enjoying the range of tutorials in this Beginners Guide to MongoDB training series.
Our previous tutorial in this series explained all about find() method in MongoDB collection.
In this tutorial, we will learn about the cursor and its methods within MongoDB in detail.
What You Will Learn:
The Cursor is a MongoDB Collection of the document which is returned upon the find method execution.
By default, it is automatically executed as a loop. However, we can explicitly get specific index document from being returned cursor. It is just like a pointer which is pointing upon a specific index value.
In simple words when we call a find method, all the documents which are returned are saved in a virtual cursor. If a find method returns for a document then it is mean that the cursor has 0 – 3 index.
In order to understand cursor, let's see an example.
In this Example, we will first check how many documents we have in our MongoDB collection. Then we will call a specific index which is returned by a cursor upon the execution of the find method with the following code.
Figure 1: In Mongo Shell
Figure 2: In Robo 3T
In the above example, it is clearly illustrated that the cursor is just like an array of the pointer which is pointing on a specific index. When we call index 0 by find method, then it returns us the first record which is placed on 0 indexes.
Count method will help us to retrieve how many records are available within a cursor. If we will place “.count()” right after the find method then it will count how many records are there.
You can observe the following Example.
Figure 3: In Mongo Shell
Figure 4: In Robo 3T
A platform provides the MongoDB limit method by which we can fetch limited records from a cursor. A cursor has thousands of documents, but we need only 2 documents so that we can limit the cursor up to 2 documents as you can see in the following Example.
Figure 5: In Mongo Shell
Figure 6: In Robo 3T
It is used to make the fetched document readable. When we execute the find method, it will return all the available documents row by row. When we append pretty method with the find method, then it will return all the documents in the form of JSON which makes data easily understandable.
Figure 7: In Mongo Shell
Figure 8: In Robo 3T
The cursor is a pointer which is used to return all the fetched record. We can explicitly call a specific index value from a cursor. We can set a limit of the cursor and count its index. We can also prettify the fetched records in order to read them easily.
In simple words, we can use it to menu play the record according to our requirements.
Our upcoming tutorial will explain all about Query Modification in MongoDB using limit!!