MongoDB Indexing & Search

MongoDB Indexing & Search

Without indexes, MongoDB performs a collection scan, which is slow for big data.

What is Indexing in MongoDB?

• Index = special data structure

• Improves query performance

• Similar to index in a book

• Stored separately from documents

 Trade-off: Faster reads, slightly slower writes

1️⃣ Create an Index

Syntax

Example: Index on name

Output:

2️⃣ Types of Indexes in MongoDB

 Single Field Index

 Compound Index (Multiple Fields)

 Order matters in compound indexes.

 Unique Index

 Prevents duplicate values.

 Text Index (Search)

Used for full-text search.

 Hashed Index

Used in sharding.

3️⃣ View Indexes

4️⃣ Drop an Index

Or drop all:

5️⃣ Search Using Indexes

Normal Search

Uses index if available.

Range Search

6️⃣ Text Search (Full-Text Search)

Create Text Index (Once)

Search Text

Sort by Relevance

7️⃣ Explain Query (Check Index Usage)

Look for:

• IXSCAN → index used

• COLLSCAN → full collection scan

8️⃣ Indexing with Aggregation

 Index on course improves $match performance.

SQL vs MongoDB Indexing

Best Practices

• Index frequently queried fields

• Use compound indexes wisely

• Avoid too many indexes

• Always check with explain()

• Place $match early in aggregation

Common Mistakes

• Creating unnecessary indexes

• Wrong field order in compound index

• Expecting text index to behave like Google search

Quick Recap