web-based photo library management software
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import sqlalchemy
import cherrypy
from cherrypy.process import plugins
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.pool import NullPool
from sqlalchemy.orm import sessionmaker
from sqlalchemy import func
Base = declarative_base()
engine_specific_options = {"sqlite": dict(connect_args={'check_same_thread': False},
poolclass=NullPool,
pool_pre_ping=True),
"mysql": dict(pool_pre_ping=True)}
def get_engine_options(uri):
for engine_prefix, options in engine_specific_options.items():
if uri.startswith(engine_prefix):
return options
return {}
def get_db_engine(uri, debug=False):
engine = sqlalchemy.create_engine(uri, **get_engine_options(uri), echo=debug)
Base.metadata.create_all(engine)
return engine
def get_db_session(uri):
engine = get_db_engine(uri)
session = sessionmaker()
session.configure(bind=engine)
return session
def driver_statement(statements):
"""
Select a value from the passed dict based on the sql driver in use. Must be used in request context. For example:
Sqlite and mysql use different date functions. This function can be used to build queries supporting either:
date_format = driver_statement({"sqlite": lambda date_format, value: func.strftime(date_format, value),
"mysql": lambda date_format, value: func.date_format(value, date_format)})
rows = db.query(PhotoSet.id, date_format('%Y-%m=%d', PhotoSet.date).label('year')).all()
:param statements: dict of driver_type->value. since sqlalchemy drivers vary per language (e.g. pymysql, pysqlite),
it is checked if the driver_type is a substring of sqlalchemy's driver name.
:type statements: dict
"""
driver = cherrypy.request.db.connection().engine.driver
for key, lambda_ in statements.items():
if key in driver:
return lambda_
raise Exception(f"Statement not supported for driver {driver}")
def date_format(date_format, value):
stmt = driver_statement({"sqlite": lambda date_format, value: func.strftime(date_format, value),
"mysql": lambda date_format, value: func.date_format(value, date_format)})
return stmt(date_format, value)
class DbAlias(object):
"""
This provides a shorter alias for the cherrypy.request.db object, which is a database session created bound to the
current request. Since the `db` attribute doesn't exist until a request is received, we cannot simply reference it
with another variable.
And instance of this class acts as an object proxy to the database object in cherrypy.request.db.
"""
def __getattr__(self, attr):
return getattr(cherrypy.request.db, attr)
db = DbAlias()
class SAEnginePlugin(plugins.SimplePlugin):
def __init__(self, bus, dbcon):
plugins.SimplePlugin.__init__(self, bus)
self.sa_engine = dbcon
self.bus.subscribe("bind", self.bind)
def start(self):
Base.metadata.create_all(self.sa_engine)
def bind(self, session):
session.configure(bind=self.sa_engine)
class SATool(cherrypy.Tool):
def __init__(self):
cherrypy.Tool.__init__(self, 'before_request_body',
self.bind_session,
priority=49) # slightly earlier than Sessions tool, which is 50 or 60
self.session = sqlalchemy.orm.scoped_session(
sqlalchemy.orm.sessionmaker(autoflush=True, autocommit=False))
def _setup(self):
cherrypy.Tool._setup(self)
cherrypy.request.hooks.attach('on_end_resource', self.commit_transaction, priority=80)
def bind_session(self):
cherrypy.engine.publish('bind', self.session)
cherrypy.request.db = self.session
def commit_transaction(self):
cherrypy.request.db = None
try:
self.session.commit()
except Exception:
self.session.rollback()
raise
finally:
self.session.remove()