Source code for chemist.managers

# -*- coding: utf-8 -*-
import sqlalchemy as db

from uuid import uuid4
from functools import partial

from chemist.exceptions import InvalidColumnName
from chemist.exceptions import InvalidQueryModifier


def escape_query(query, escape='#'):
    for c in ('%', '_', '/'):
        query = query.replace(c, '{}{}'.format(escape, c))
    return query


[docs]class Manager(object): """ """ def __init__(self, model_klass, context): self.model = model_klass self.context = context self.engine = context.engine
[docs] def from_result_proxy(self, proxy, result): """Creates a new instance of the model given an instance of :py:class:`sqlalchemy.engine.ResultProxy`""" if not result: return None data = dict(zip(proxy.keys(), result)) return self.model(engine=self.engine, **data)
def many_from_result_proxy(self, proxy): Models = partial(self.from_result_proxy, proxy) return list(map(Models, proxy.fetchall()))
[docs] def create(self, **data): """Creates a new model and saves it to MySQL""" colmeta = getattr(self.model, '__columns__', {}) cols = colmeta.keys() if 'uuid' in cols and 'uuid' not in data: data['uuid'] = uuid4().hex instance = self.model(engine=self.engine, **data) return instance.save()
[docs] def get_or_create(self, **data): """Tries to get a model from the database that would match the given keyword-args through :py:meth:`Manager.find_one_by`. If not found, a new instance is created in the database through :py:meth:`Manager.create`""" instance = self.find_one_by(**data) if not instance: instance = self.create(**data) return instance
[docs] def generate_query( self, order_by=None, limit_by=None, offset_by=None, **kw): """Queries the table with the given keyword-args and optionally a single order_by field.""" query = self.model.table.select() for field, value in kw.items(): if callable(value): value = value() if hasattr(self.model.table.c, field): query = query.where(getattr(self.model.table.c, field) == value) elif '__' in field: field, modifier = field.split('__', 1) f = getattr(self.model.table.c, field) if modifier == 'startswith': query = query.where(f.startswith(value)) elif modifier == 'contains': contains = f.contains(escape_query(value), escape='#') query = query.where(contains) else: msg = '"{}" is in invalid query modifier.'.format(modifier) raise InvalidQueryModifier(msg) else: msg = 'The field "{}" does not exist.'.format(field) raise InvalidColumnName(msg) if isinstance(limit_by, (float, int)): query = query.limit(limit_by) if isinstance(offset_by, (float, int)): query = query.offset(offset_by) # Order the results db_order = db.desc if order_by: if order_by.startswith('+'): order_by = order_by[1:] db_order = db.asc elif order_by.startswith('-'): order_by = order_by[1:] query = query.order_by(db_order( getattr(self.model.table.c, order_by or self.model.get_pk_name()) )) return query
def prepare_where_clause(self, *expressions, **kwargs): order_by = kwargs.pop('order_by', None) table = self.model.table query = table.select() for exp in expressions: query = query.where(exp) if isinstance(order_by, tuple): query = query.order_by(*order_by, **kwargs) elif order_by is not None: raise TypeError('order_by must be a tuple of SQLAlchemy columns optionally wrapped in asc/desc modifiers') return query def where_many(self, *expressions, **kwargs): query = self.prepare_where_clause(*expressions, **kwargs) return self.many_from_query(query) def where_one(self, *expressions, **kwargs): query = self.prepare_where_clause(*expressions, **kwargs) return self.one_from_query(query)
[docs] def query_by(self, **kwargs): """This method is used internally and is not consistent with the other ORM methods by not returning a model instance.""" conn = self.get_connection() query = self.generate_query(**kwargs) proxy = conn.execute(query) return proxy
def many_from_query(self, query): conn = self.get_connection() proxy = conn.execute(query) return self.many_from_result_proxy(proxy) def one_from_query(self, query): conn = self.get_connection() proxy = conn.execute(query) return self.from_result_proxy(proxy, proxy.fetchone())
[docs] def find_one_by(self, **kw): """Find a single model that could be found in the database and match all the given keyword-arguments""" proxy = self.query_by(**kw) return self.from_result_proxy(proxy, proxy.fetchone())
[docs] def find_by(self, **kw): """Find a list of models that could be found in the database and match all the given keyword-arguments""" proxy = self.query_by(**kw) Models = partial(self.from_result_proxy, proxy) return list(map(Models, proxy.fetchall()))
[docs] def all(self, limit_by=None, offset_by=None, order_by=None): """Returns all existing rows as Model""" return self.find_by( limit_by=limit_by, offset_by=offset_by, order_by=order_by, )
[docs] def total_rows(self, field_name=None, **where): """Gets the total number of rows in the table""" field_name = field_name or self.model.get_pk_name() conn = self.get_connection() query = self.model.table.count() for key, value in where.items(): field = getattr(self.model.table.c, key, None) if field is not None: query = query.where(field == value) proxy = conn.execute(query) return proxy.scalar()
def get_connection(self): return self.engine.connect()