kevinjqiu

Request handling models

Abstraction layer

• What is wsgi

PEP3333, a web server gateway interface, specifies how web server should communicate with web applications and how web applications can be chained together to process one request

• Benefit?

kevinjqiu

MySQL demystified

How does MySQL execute queries?

• SQL => Parse Tree => Execution plan
• The execution plan is a data structure, not byte-code
• The executor makes storage engine calls

Execution plan

"Deep left tree" -- always

Explain output columns

kevinjqiu

from pretenders.server.server import run 
import multiprocessing                                                                                                                                         


ml = multiprocessing.Process(name='ml', target=run)
ml.start()


def _init():
    from pretenders.client.http import HTTPMock

kevinjqiu

verisign,PayPal Payflow Pro,Lucre
paypaldirect,PayPal direct,lucre
paypalexpress,PayPal Express,offsite
paypaladaptive,PayPal,asynchronous
paypaladaptiveb2b,PayPal,asynchronous

kevinjqiu

class AppendOnlyModelMeta(DeclarativeMeta):
    @staticmethod
    def _get_append_only_attributes(cls):
        '''A helper method to get a list of append-only attributes
        declared on the class.'''
        [...]

    def __init__(cls, classname, bases, dict_):
        if hasattr(cls, '__history_class__'):
            cls._history_fields = cls._get_append_only_attributes(cls)

kevinjqiu

class Transaction:
    class History:
        id
        transaction_id
        status

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

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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)

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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):

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

    source_id = ...

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

transaction = get_transaction()
print(transaction.status)