Document ID strategies in Firebase - Step-by-Step Execution

Process Flow - Document ID strategies

Start Document Creation

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Choose ID Strategy

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Auto-ID

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Generate

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Save Document with ID

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End

This flow shows how a document ID is chosen when creating a document: either auto-generated, custom provided, or composed from fields, then saved.

Execution Sample

Firebase

db.collection('users').doc().set({name: 'Ana'})
db.collection('users').doc('user123').set({name: 'Bob'})
db.collection('users').doc(user.email + '_profile').set({name: 'Cara'})

Creates three documents in 'users' collection using auto-generated ID, custom ID, and composite ID.

Process Table

Step	Action	Document ID	Result
1	Create doc with auto-ID	auto-generated (e.g. 'XyZ123')	Document saved with auto-generated ID
2	Create doc with custom ID 'user123'	user123	Document saved with ID 'user123'
3	Create doc with composite ID '[e-mail]_profile'	[e-mail]_profile	Document saved with composite ID
4	End	-	All documents created successfully

💡 All documents created with chosen ID strategies

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
docID	none	auto-generated string	user123	[e-mail]_profile	final IDs assigned

Key Moments - 3 Insights

Why does the first document have a strange ID like 'XyZ123'?

Because in step 1, the ID was auto-generated by Firebase, as shown in execution_table row 1.

Can I use any string as a custom document ID?

Yes, but it must be unique in the collection and cannot contain slashes. This is shown in step 2 where 'user123' is used.

What is a composite ID and why use it?

A composite ID combines fields like email and suffix to create a meaningful unique ID, as in step 3.

Visual Quiz - 3 Questions

Look at the execution_table, what type of ID is assigned at step 1?

A Composite ID

B Custom ID

C Auto-generated ID

D No ID assigned

💡 Hint

Check the 'Document ID' column in execution_table row 1

At which step is the document ID explicitly set by the user?

A Step 1

B Step 2

C Step 4

D Step 3

💡 Hint

Look for 'custom ID' in the 'Action' column in execution_table

If you want to create a document ID combining user email and '_profile', which step shows this?

A Step 3

B Step 2

C Step 1

D Step 4

💡 Hint

See 'composite ID' in execution_table row 3

Concept Snapshot

Document ID strategies in Firebase:
- Auto-ID: Firebase generates a unique ID automatically.
- Custom ID: You provide a unique string as the document ID.
- Composite ID: Combine fields (like email + suffix) to form an ID.
Choose based on uniqueness and readability needs.
IDs must be unique within a collection.

Full Transcript

When creating documents in Firebase, you must decide how to assign the document ID. You can let Firebase generate a unique ID automatically, which looks like a random string. Alternatively, you can provide your own custom ID string, which must be unique and cannot contain slashes. Another option is to create a composite ID by combining meaningful fields, such as a user's email plus a suffix. This helps keep IDs readable and unique. The execution table shows three steps creating documents with these strategies, tracking the assigned IDs and results. Understanding these options helps you organize your database effectively.