MongoDB Indexes: Deep Dive, Understanding Indexes.

Getting a performance boost with the best usage of indexes, by understanding what’s the data structure, how it works’s/stored, how is it loaded into memory. How Query optimization make’s decision to select indexes.

Getting a performance boost with the best usage of indexes, by understanding what’s the data structure, how it works’s/stored, how is it loaded into memory. How Query optimization make’s decision to select indexes.

_Basic understanding of indexes is required i.e what are indexes, index types, creating them. [https://docs.mongodb.com/manual/indexes/_](https://docs.mongodb.com/manual/indexes/)

• Data Structure
• Storage on disk
• Memory Allocation.

Data Structure

Index on a filed/fields is stored in order that we specify using B-Tree data structure. Stored in ordered Let see what does it mean’s and how it help’s.

• Index is created on the value of the filed referencing to the actual document stored.

  

snipped from: MognoDB university

• Using B-Tree indexes significantly reduces the number of comparison to find the document.

  

snipped from: MognoDB university

• Likewise in below picture we can see with index(sky blue line) even adding document still limit the number of document examined in comparison to without index/collscan.

  

snipped from: MognoDB university

Storage On Disk

Let’s see/visualize how the index are stored on disk. Index stored on disk is managed by the database storage engine itself.

• Uses prefix Index compression- Repeated prefix value is not written, let us see example to understand what it mean’s.

db.getCollection("movieTicket")
.ensureIndex({"showDate":1, "seatNo":1, "status":1});

How the index ({“showDate”:1, “seatNo”:1, “status”:1}) is stored on disk.

showDate_1_seatNo_1_status_1

index mongodb indexing mongo

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ＬＩＫＥ | ＣＯＭＭＥＮＴ | ＳＨＡＲＥ | ＳＵＢＳＣＲＩＢＥIn this tutorial, I will discuss the basic query or command of MongoDB Database. We will learn how to Create, Delete, and ...