Difference Between Firestore Set with {merge: true} and Update

Difference Between Firestore Set with {merge: true} and Update

🔥✍️ Welcome back to my tech blog! Today, we are going to dive into the wonderful world of Cloud Firestore and explore the difference between two write operations: set() with { merge: true } and update().

In Firestore, there are three main write operations: add(), set(), and update(). add() is used to create a new document, set() is used to either create a new document or completely overwrite an existing document, and update() is used to modify an existing document. But what about the { merge: true } option with set()? Let's find out!

✅ Understanding set(object, { merge: true })

According to the Firestore documentation, set(object, { merge: true }) allows us to merge the given object with the existing document. This means that if the document exists, only the specified fields will be updated, while the rest of the document remains untouched.

For example, let's say we have a document with the following fields:

{
  name: "John",
  age: 25,
  city: "New York"
}

If we use set({ age: 26 }, { merge: true }) on this document, only the age field will be updated:

{
  name: "John",
  age: 26,
  city: "New York"
}

The name and city fields remain unchanged. This merging behavior is great when you only want to update specific fields without affecting the rest of the document.

🚀 Exploring update(object)

Now, let's take a look at update(object). This operation is used to modify the existing fields of a document or create them if they don't exist. Unlike set(), update() does not overwrite the entire document. Instead, it selectively modifies the specified fields, leaving the rest untouched.

Continuing with our previous example, if we use update({ age: 26 }), the resulting document will be the same as before:

{
  name: "John",
  age: 26,
  city: "New York"
}

Both set({ age: 26 }, { merge: true }) and update({ age: 26 }) achieve the same result of updating the age field. However, update() can be used to modify multiple fields at once:

update({
  age: 26,
  city: "San Francisco"
})

This will update both the age and city fields while leaving the name field unchanged:

{
  name: "John",
  age: 26,
  city: "San Francisco"
}

😲 Why Duplicated Functionality?

You might be wondering why Firestore provides two operations that seem to have duplicate functionality. Well, each operation has its own use cases and benefits.

set(object, { merge: true }) is ideal when you want to update specific fields without touching the rest of the document. It provides a fine-grained control over updates and can help optimize performance by reducing the amount of data that needs to be transferred.

On the other hand, update(object) is great when you need to modify multiple fields at once or if you're uncertain about the existence of certain fields. It simplifies the update process by automatically creating fields if they don't already exist.

🔓 Easy Solutions to Common Issues

Now that you understand the difference between set(object, { merge: true }) and update(object), let's address some common issues you may encounter:

1. Overwriting Document: If you want to completely replace the existing document with a new one, use set(object) without the { merge: true } option.

2. Invalid Field Name: When using update(), make sure to specify valid field names. Otherwise, Firestore will throw an error.

3. Field Deletion: To delete a field, you can set its value to FieldValue.delete(). For example, update({ age: FieldValue.delete() }) will remove the age field from the document.

🙌 Engage with the Tech Community

I hope this guide has cleared up any confusion you had about the difference between set(object, { merge: true }) and update(object) in Firestore. Now it's time for you to put your new knowledge into practice!

Do you have any questions, tips, or personal experiences with Firestore? Share them in the comments below and let's spark a meaningful conversation. Together, we can unlock the true potential of Firestore!

Keep exploring, keep learning, and stay tuned for more exciting tech content. See you in the next post! 🎉🌟👋