Increment operations in Firebase - Step-by-Step Execution

Process Flow - Increment operations

Start with initial value

↓

Read current value

↓

Add increment amount

↓

Write new value back

↓

Operation complete

Increment operations read a value, add a number, then save the new value back.

Execution Sample

Firebase

const increment = firebase.firestore.FieldValue.increment(1);
db.collection('counters').doc('pageViews').update({ count: increment });

This code increases the 'count' field in the 'pageViews' document by 1.

Process Table

Step	Action	Current Value	Increment Amount	New Value	Result
1	Read 'count' field	5	N/A	N/A	Current value is 5
2	Apply increment	5	1	6	Add 1 to 5 equals 6
3	Write new value	N/A	N/A	6	Updated 'count' to 6
4	Operation complete	6	N/A	6	Increment operation finished

💡 Increment operation stops after writing the new value back to the database.

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
count	5	5	5	6	6
incrementAmount	1	1	1	1	1

Key Moments - 2 Insights

Why does the increment operation not require reading the value manually before updating?

Firebase's increment operation is atomic and server-side, so it handles reading and updating internally as shown in execution_table step 2 and 3.

What happens if the 'count' field does not exist before incrementing?

Firebase treats missing fields as zero, so incrementing will create the field with the increment amount, similar to starting at 0 in execution_table step 1.

Visual Quiz - 3 Questions

Look at the execution table, what is the 'count' value after step 2?

A 1

B 5

C 6

D N/A

💡 Hint

Check the 'New Value' column at step 2 in the execution_table.

At which step is the new incremented value written back to the database?

A Step 3

B Step 2

C Step 1

D Step 4

💡 Hint

Look for the action 'Write new value' in the execution_table.

If the increment amount was changed to 3, what would be the new value after step 2 assuming the start was 5?

A 5

B 8

C 3

D 6

💡 Hint

Add the increment amount to the current value as shown in step 2.

Concept Snapshot

Increment operations in Firebase:
- Use FieldValue.increment(amount) to add atomically.
- No need to read value manually.
- Handles missing fields as zero.
- Updates happen server-side safely.
- Example: update({count: increment(1)}) adds 1.

Full Transcript

Increment operations in Firebase allow you to add a number to a field safely without reading it first. The process starts by reading the current value, then adding the increment amount, and finally writing the new value back. Firebase handles this atomically on the server, so you don't have to worry about conflicts. If the field does not exist, it treats it as zero and creates it with the increment amount. This makes increment operations simple and safe for counters and similar use cases.