Updating Only the expire_date Field in Django

Yes, you can update only the expire_date field in Django using either the update_fields parameter with save() or the update() method. Let me explain both approaches.

Using update_fields (Your Current Approach)

Your current approach is correct:

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session = Session.objects.get(id=1)
session.expire_date = datetime.now() + timedelta(days=30)
session.save(update_fields=['expire_date'])

This will only update the expire_date field in the database. The update_fields parameter tells Django to only include the specified fields in the SQL UPDATE statement, which is exactly what you want.

Using QuerySet.update() (More Efficient)

A more efficient approach would be to use the update() method, which performs an SQL update query directly without loading the model instance into memory:

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from datetime import datetime, timedelta

# Update a specific session
Session.objects.filter(id=1).update(
    expire_date=datetime.now() + timedelta(days=30)
)

This approach has several advantages:

1. It's more efficient as it doesn't require fetching the object first
2. It avoids race conditions that might occur between fetching and saving
3. It performs the update at the SQL level in a single query

Comparing Your Raw SQL Approach

Your raw SQL approach:

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with connection.cursor() as cursor:
    cursor.execute("""
        UPDATE django_session
        SET expire_date = TIMESTAMPADD(SECOND, %s, NOW())
        WHERE session_key = %s
    """, [settings.SESSION_COOKIE_AGE, session_key])

While this works, using Django's ORM methods (update() or save(update_fields=[...])) is generally preferred because:

1. It's more portable across different database backends
2. It's more maintainable and readable
3. It integrates better with Django's ecosystem

Important Considerations

When using update():

• It operates at the SQL level and doesn't call any save() methods on your models
• It doesn't emit pre_save or post_save signals
• It returns the number of rows affected by the update
• It can only update columns in the model's main table

If you need the signals or custom save() logic to run, use the save(update_fields=[...]) approach. Otherwise, update() is generally more efficient.

Recommendation

For your specific use case, I recommend using the update() method:

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Session.objects.filter(session_key=session_key).update(
    expire_date=datetime.now() + timedelta(seconds=settings.SESSION_COOKIE_AGE)
)

This is the most efficient and Django-idiomatic way to update just the expire_date field.