How to Understand Index Performance?

In this tutorial, we will learn How to understand index performance, where we have to use explain() method to generate the plans of query which is ultimately used for getting the information about the indexes whether it is using indexes or not.


Index performance

Here there are certain steps that we need to follow for understanding the performance of the index using explain method so here we will follow the steps given to get to know the index performance.

As indexing is really helpful in getting the information by reducing the timing of searching as it gives a direct way to access the collection as indexes store the short information of each collection and as we know that there are different types of indexing.

Steps for getting the performance of an index

  1. Run a query: First, we need to run a query for which we want to analyze the index performance take an example of code given below where


db. collection. find({ field: value })

2. Use explain() method it is the method used for generating the query for the query plan.

db.collection.find({ field: value }).explain()

Examine the output of the query plan to see if the query used an index, which index it used, and how many documents were scanned.

Here are some key parameters to look for in the query plan:

Indicates the number of documents that were examined during the query execution.

  • execution Docs examined: Indicates the time taken to execute the query in milliseconds.
  • Winning plan: This shows the plan chosen by the MongoDB query optimizer.
  • Stage: Shows the stage of the query execution.
  • Index Bounds: Shows the range of index keys used to satisfy the query.

If the query uses an index, you should look for the callscan keyword in the query plan, which indicates that the query did not use an index and scanned the entire collection. If the query uses an index, you should check whether the index used covers the query, meaning all the fields required by the query are included in the index.


To learn more about Understand Index performance visit:  The Indexes by stack overflow.

To learn more about MongoDB and solutions related to Database management systems visit: MongoDB Problems And Tutorials.

To learn more about different other programming languages like Python, Java, and SQL as solutions to the problems and concepts as tutorials you may visit: beta python programming languages Solutions.

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