Firestore collections and documents in GCP - Step-by-Step Execution

Process Flow - Firestore collections and documents

Start

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Create Collection

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Add Document

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Document Contains Fields

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Add Subcollection?

Yes→Create Subcollection

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Add Document

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Read/Update/Delete Document

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End

This flow shows how you create a collection, add documents with fields, optionally add subcollections, and then read or modify documents.

Execution Sample

GCP

db.collection('users').doc('user1').set({name: 'Ana', age: 30})

This code creates a 'users' collection, adds a document with ID 'user1', and sets fields 'name' and 'age'.

Process Table

Step	Action	Collection	Document ID	Fields Added	Result
1	Create collection reference	users	-	-	Reference to 'users' collection created
2	Create document reference	users	user1	-	Reference to document 'user1' created
3	Set document fields	users	user1	{name: 'Ana', age: 30}	Document 'user1' created with fields
4	Add subcollection reference?	users/user1/orders	-	-	Subcollection 'orders' can be created under 'user1'
5	Add document to subcollection	users/user1/orders	order1	{item: 'book', qty: 1}	Document 'order1' added to subcollection
6	Read document	users	user1	-	Fields returned: {name: 'Ana', age: 30}
7	Update document field	users	user1	{age: 31}	Field 'age' updated to 31
8	Delete document	users	user1	-	Document 'user1' deleted
9	Attempt to read deleted document	users	user1	-	Document not found
10	End	-	-	-	No more actions

💡 Execution stops after document deletion and failed read confirms removal.

Status Tracker

Variable	Start	After Step 3	After Step 5	After Step 7	After Step 8	After Step 9
users collection	empty	contains doc 'user1'	contains doc 'user1' with subcollection 'orders'	contains doc 'user1' with updated age	doc 'user1' deleted	doc 'user1' not found
user1 document fields	none	{name: 'Ana', age: 30}	{name: 'Ana', age: 30}	{name: 'Ana', age: 31}	deleted	not found
orders subcollection	none	none	contains doc 'order1'	contains doc 'order1'	contains doc 'order1'	contains doc 'order1'

Key Moments - 3 Insights

Why does the document 'user1' still exist after adding a subcollection?

Adding a subcollection under 'user1' does not delete or replace the 'user1' document itself, as shown in steps 4 and 5 where 'user1' still has its fields.

What happens if you try to read a document after deleting it?

As seen in step 9, reading a deleted document returns 'Document not found' because the document no longer exists in the collection.

Can a collection exist without documents?

Yes, a collection reference can exist before any documents are added, as in step 1 where the 'users' collection is referenced but empty.

Visual Quiz - 3 Questions

Look at the execution table, what fields does document 'user1' have after step 3?

A {name: 'Ana', age: 30}

B {item: 'book', qty: 1}

C No fields, document is empty

D Document deleted

💡 Hint

Check the 'Fields Added' column at step 3 in the execution table.

At which step does the 'age' field of 'user1' get updated?

A Step 3

B Step 7

C Step 5

D Step 9

💡 Hint

Look for the step where 'Update document field' action happens in the execution table.

If we delete the document 'user1' at step 8, what happens when we try to read it at step 9?

A Returns the original fields

B Returns updated fields

C Returns 'Document not found'

D Returns subcollection documents

💡 Hint

Check the 'Result' column at step 9 in the execution table.

Concept Snapshot

Firestore stores data in collections and documents.
Collections hold documents; documents hold fields.
Documents can have subcollections.
Create collection > add document with fields > optionally add subcollections.
Read, update, or delete documents anytime.
Deleting a document removes its fields but not necessarily its subcollections.

Full Transcript

Firestore organizes data in collections and documents. You start by creating a collection reference, then add documents identified by unique IDs. Each document holds fields, which are key-value pairs like name and age. Documents can also have subcollections, which are collections nested under a document. You can read, update, or delete documents. Deleting a document removes its fields and the document itself, but subcollections remain unless explicitly deleted. This flow helps manage structured data in Firestore efficiently.