MongoIndexer

Automatic MongoDB Index Creation from Go Struct Tags

mongoindexer is a lightweight and idiomatic Go package that automatically creates MongoDB indexes based on struct tags. It’s designed to be generic, testable, and easy to integrate with any MongoDB project — no manual index management required.

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Features

• Automatically parses struct tags to generate indexes.
• Supports unique, ascending/descending, and TTL indexes.
• Simple, interface-based design for testing and extensibility.
• Fully covered with unit tests using testify.

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Installation

go get github.com/bhupenderlost/mongoindexer

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Usage

1. Define your struct

Add the mongoIndex tag to specify index configuration.

package main

type User struct {
    Email     string `bson:"email" mongoIndex:"unique,asc,name=email_idx"`
    CreatedAt int64  `bson:"created_at" mongoIndex:"ttl=3600"`
}

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2. Create indexes

package main

import (
    "context"
    "log"

    "github.com/bhupenderlost/mongoindexer"
    "go.mongodb.org/mongo-driver/mongo"
    "go.mongodb.org/mongo-driver/mongo/options"
)

func main() {
    ctx := context.Background()

    client, err := mongo.Connect(ctx, options.Client().ApplyURI("mongodb://localhost:27017"))
    if err != nil {
        log.Fatal(err)
    }

    db := client.Database("testdb")
    coll := db.Collection("users")

    indexer := mongoindexer.New()
  	wrapped := mongoindexer.WrapCollection(coll)

    if err := indexer.CreateIndexes(ctx, wrapped, User{}); err != nil {
        log.Fatal("Index creation failed:", err)
    }

    log.Println("Indexes created successfully!")
}

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Tag Syntax

Option	Description	Example
asc / desc	Index order (ascending / descending)	mongoIndex:"asc"
unique	Creates a unique index	mongoIndex:"unique,asc"
ttl=<sec>	Sets a TTL (Time-to-Live) index	mongoIndex:"ttl=3600"
name=<idx>	Custom index name	mongoIndex:"unique,asc,name=email"

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Testing

This package comes with a complete set of unit tests using testify and mock.

Run tests with:

go test ./...

Example test:

func TestCreateIndexes_Success(t *testing.T) {
    // mock IndexView, verify that CreateMany was called
}

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Project Structure

indexer/
│
├── indexer.go            # Core logic for parsing and creating indexes
├── parser.go             # Tag parsing and validation
├── interfaces.go         # Mongo interfaces for abstraction
└── indexer_test.go       # Unit tests using testify mocks for indexer
└── parser_test.go        # Unit tests using testify mocks for parser

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Design Philosophy

• Interfaces-first: Easily mockable for testing (CollectionAPI, IndexView).
• Generic: Works with any MongoDB collection that implements the minimal interface.
• Declarative: Indexes are defined once in the struct — no manual duplication.

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Example Output

When executed with the example User struct, the following indexes are created:

[
  {
    "key": { "email": 1 },
    "name": "email_idx",
    "unique": true
  },
  {
    "key": { "created_at": 1 },
    "expireAfterSeconds": 3600
  }
]

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Contributing

1. Fork the repository.

2. Create a feature branch:

   git checkout -b feature/awesome-index

3. Commit your changes:

   git commit -m "feat: add new index rule"

4. Push and open a PR

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License

Licensed under the MIT License.
See LICENSE for more information.