Insert Documents

Introduction

Inserting is how data enters a MongoDB collection. The two workhorses are insertOne and insertMany. Both return acknowledgements with the generated _ids, and both are atomic per document.

Understanding the topic

• insertOne(doc) — single document, returns inserted _id.
• insertMany([...]) — batch insert, ordered by default.
• Pass { ordered: false } to continue on errors.
• Server generates ObjectId if no _id supplied.
• Inserts respect schema validators and indexes (including unique).

Syntax reference

db.users.insertOne({ name: "Ada", email: "ada@x.com" });

db.products.insertMany([
  { sku: "A1", price: 9.99 },
  { sku: "A2", price: 19.99 }
], { ordered: false });

Real-world use

Batch ETL jobs use insertMany({ ordered: false }) to skip duplicates without aborting the whole batch.

Best practices

• Batch inserts when possible — fewer round-trips.
• Use ordered: false for resilient bulk loads.

Common mistakes

• Re-inserting an existing _id throws — use upsert instead.