SQLAlchemy Object Lifecycle — Part 1

Recall

We can insert new records into the database using SQLAlchemy by running

person = Person(name='Amy')
db.session.add(person)
db.session.commit()

which will build a transaction for inserting in a person instance in our model/table, and persist it to the database upon calling commit() .

Takeaways

• Within a session, we create transactions every time we want to commit work to the database.
• Proposed changes are not immediately committed to the database and instead go through stages to allow for undos.
• The ability to undo is allowed via db.session.rollback()

Stages:

1. Transient : an object exists, it was defined.

  user1 = User(name='Amy')

…but not attached to a session (yet).

2. Pending : an object was attached to a session. "Undo" becomes available via db.session.rollback() . Waits for a flush to happen

3. Flushed : about ready to be committed to the database, translating actions into SQL command statements for the engine.

4. Committed : manually called for a change to persist to the database (permanently); session's transaction is cleared for a new set of changes.

QUIZ QUESTION: :

Match the statement to the stage that an object would be in its lifecycle, if the statement was called

ANSWER CHOICES:

QUIZ QUESTION: :

Order the stages in correct order

ANSWER CHOICES: