kevinjqiu

INSERT INTO transaction VALUES(...);
INSERT INTO transaction_history
        (id, transaction_id, status)
        VALUES (1, 't1', 'opened');

kevinjqiu

SELECT * FROM transaction WHERE id='t1';
SELECT * FROM transaction_history WHERE transaction_id='t1';

kevinjqiu

INSERT INTO transaction_history
    (id, transaction_id, status)
    VALUES (2, 't1', 'unverified');

kevinjqiu

+--+----------+---------------+-------+---------+
|id| source_id| destination_id| amount| currency|
+--+----------+---------------+-------+---------+
|t1|    b1    |     b2        |  780  |  USD    |
|t2|    b3    |     b4        |  9900 |  CAD    |
+--+----------+---------------+-------+---------+

+-------+-----------------+---------------------+                                            
|  id   |    status       |    transaction_id   | 
+-------+-----------------+---------------------+

kevinjqiu

SELECT
    "transaction".id, "transaction".amount,
    "transaction".currency, current_status.status
FROM "transaction" JOIN (
    SELECT                                                                                   
        transaction_id, MAX(id) AS max_id
    FROM transaction_history
    GROUP BY transaction_id) max_ids JOIN (
    SELECT
        id, transaction_id, status

kevinjqiu

transaction = create_transaction()
transaction.status = 'unverified'

transaction = get_transaction()
print(transaction.status)

kevinjqiu

class Transaction(AppendOnlyModel):
    __tablename__ = 'transaction'
    __history_class__ = make_history_class(
        'transaction',
        status=HistoryStateColumn(
            sa.Enum(*constants.TRANSACTION_STATUSES),
            nullable=False)
    )

    source_id = ...

kevinjqiu

class AgeAttr(object):
    def __get__(self, instance, owner):
        return instance.value

    def __set__(self, instance, value):
        if value < 0:
            raise ValueError('Age cannot be negative')
        instance.value = value

class User(object):

kevinjqiu

class _AppendOnlyAttribute(object):
    def __init__(self, name):
        self.name = name

    def __get__(self, instance, owner):
        if instance:
            return getattr(instance._history[0], self.name)
        else:
            return getattr(owner.__history_class__, self.name)

kevinjqiu

class Transaction:
    class History:
        id
        transaction_id
        status

    _history = relation(
        History,
        and_(History.transaction_id == Transaction.transaction_id))