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smartquery.py
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smartquery.py
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from __future__ import print_function
import os
import datetime
import sqlalchemy as sa
from sqlalchemy import create_engine
from sqlalchemy.ext.hybrid import hybrid_method
from sqlalchemy.ext.hybrid import hybrid_property
from sqlalchemy.orm import Query, scoped_session, sessionmaker, DeclarativeBase
from sqlalchemy_mixins import SmartQueryMixin, ReprMixin, JOINED, smart_query
def log(msg):
print('\n{}\n'.format(msg))
#################### setup ######################
class Base(DeclarativeBase):
__abstract__ = True
# we also use ReprMixin which is optional
class BaseModel(Base, SmartQueryMixin, ReprMixin):
__abstract__ = True
__repr__ = ReprMixin.__repr__
pass
class User(BaseModel):
__tablename__ = 'user'
__repr_attrs__ = ['name']
id = sa.Column(sa.Integer, primary_key=True)
name = sa.Column(sa.String)
# to smart query relationship, it should be explicitly set,
# not to be a backref
posts = sa.orm.relationship('Post')
comments = sa.orm.relationship('Comment')
# below relationship will just return query (without executing)
# this query can be customized
# see http://docs.sqlalchemy.org/en/latest/orm/collections.html#dynamic-relationship
#
# we will use this relationship for demonstrating real-life example
# of how smart_query() function works (see 3.2.2)
comments_ = sa.orm.relationship('Comment', lazy="dynamic") # this will return query
class Post(BaseModel):
__tablename__ = 'post'
id = sa.Column(sa.Integer, primary_key=True)
body = sa.Column(sa.String)
user_id = sa.Column(sa.Integer, sa.ForeignKey('user.id'))
archived = sa.Column(sa.Boolean, default=False)
# to smart query relationship, it should be explicitly set,
# not to be a backref
user = sa.orm.relationship('User')
comments = sa.orm.relationship('Comment')
@hybrid_property
def public(self):
return not self.archived
@public.expression
def public(cls):
return ~cls.archived
@hybrid_method
def is_commented_by_user(cls, user, mapper=None):
# in real apps, Comment class can be obtained from relation
# to avoid cyclic imports like so:
# Comment = cls.comments.property.argument()
mapper = mapper or cls
# from sqlalchemy import exists
# return exists().where((Comment.post_id == mapper.id) & \
# (Comment.user_id == user.id))
return mapper.comments.any(Comment.user_id == user.id)
@hybrid_method
def is_public(cls, value, mapper=None):
# in real apps, Comment class can be obtained from relation
# to avoid cyclic imports like so:
# Comment = cls.comments.property.argument()
mapper = mapper or cls
return mapper.public == value
class Comment(BaseModel):
__tablename__ = 'comment'
__repr_attrs__ = ['body']
id = sa.Column(sa.Integer, primary_key=True)
body = sa.Column(sa.String)
user_id = sa.Column(sa.Integer, sa.ForeignKey('user.id'))
post_id = sa.Column(sa.Integer, sa.ForeignKey('post.id'))
rating = sa.Column(sa.Integer)
created_at = sa.Column(sa.DateTime)
# to smart query relationship, it should be explicitly set,
# not to be a backref
user = sa.orm.relationship('User')
post = sa.orm.relationship('Post')
#################### setup ORM ######################
db_file = os.path.join(os.path.dirname(__file__), 'test.sqlite')
engine = create_engine('sqlite:///{}'.format(db_file), echo=True)
Base.metadata.drop_all(engine)
Base.metadata.create_all(engine)
session = scoped_session(sessionmaker(bind=engine))
BaseModel.set_session(session)
#################### setup some data ######################
u1 = User(name='Bill u1')
session.add(u1)
session.commit()
u2 = User(name='Alex u2')
session.add(u2)
session.commit()
u3 = User(name='Bishop u3')
session.add(u3)
session.commit()
session.commit()
p11 = Post(
id=11,
body='1234567890123',
archived=True,
user=u1
)
session.add(p11)
session.commit()
p12 = Post(
id=12,
body='1234567890',
user=u1
)
session.add(p12)
session.commit()
p21 = Post(
id=21,
body='p21',
user=u2
)
session.add(p21)
session.commit()
p22 = Post(
id=22,
body='p22',
user=u2
)
session.add(p22)
session.commit()
cm11 = Comment(
id=11,
body='cm11',
user=u1,
post=p11,
rating=1,
created_at=datetime.datetime(2014, 1, 1)
)
session.add(cm11)
session.commit()
cm12 = Comment(
id=12,
body='cm12',
user=u2,
post=p12,
rating=2,
created_at=datetime.datetime(2015, 10, 20)
)
session.add(cm12)
session.commit()
cm21 = Comment(
id=21,
body='cm21',
user=u1,
post=p21,
rating=1,
created_at=datetime.datetime(2015, 11, 21)
)
session.add(cm21)
session.commit()
cm22 = Comment(
id=22,
body='cm22',
user=u3,
post=p22,
rating=3,
created_at=datetime.datetime(2016, 11, 20)
)
session.add(cm22)
session.commit()
cm_empty = Comment(
id=29,
# no body
# no user
# no post
# no rating
)
session.add(cm_empty)
session.commit()
#################### Demo ######################
# ['id', 'body', 'user_id', 'archived', # normal columns
# 'user', 'comments', # relations
# 'public', # hybrid attributes
# 'is_public', 'is_commented_by_user' # hybrid methods
# ]
log(Post.filterable_attributes)
#### 1. Filters ####
##### 1.1 filter by hybrid_property 'public' #####
# low-level filter_expr()
log(session.query(Post).filter(*Post.filter_expr(user=u1, public=True)).all())
# high-level SmartQueryMixin.where() method
log(Post.where(user=u1, public=True).all())
# you can unpack dict (in real world app you will do this)
filters = {'user': u1, 'public': True}
log(Post.where(**filters).all())
##### 1.2 filter by hybrid_method 'is_commented_by_user' #####
# low-level filter_expr()
log(session.query(Post).filter(
*Post.filter_expr(is_commented_by_user=u1)).all())
# high-level SmartQueryMixin.where() method
log(Post.where(is_commented_by_user=u1).all())
##### 1.3 operators #####
# rating == None
log(Comment.where(rating=None).all()) # cm_empty
log(Comment.where(rating__isnull=2).all()) # cm_empty
# rating == 2
# when no operator, 'exact' operator is assumed
log(Comment.where(rating=2).all()) # cm12
# assumed
log(Comment.where(rating__exact=2).all()) # cm12
# rating > 2
log(Comment.where(rating__gt=2).all()) # cm22
# rating >= 2
log(Comment.where(rating__ge=2).all()) # cm12, cm22
# rating < 2
log(Comment.where(rating__lt=2).all()) # cm11, cm21
# rating <= 2
log(Comment.where(rating__le=2).all()) # cm11, cm12, cm21
# rating in [1,3]
log(Comment.where(rating__in=[1, 3]).all()) # cm11, cm21, cm22
log(Comment.where(rating__in=(1, 3)).all()) # cm11, cm21, cm22
log(Comment.where(rating__in={1, 3}).all()) # cm11, cm21, cm22
# rating between 2 and 3
log(Comment.where(rating__between=[2, 3]).all()) # cm12, cm22
log(Comment.where(rating__between=(2, 3)).all()) # cm12, cm22
# likes
log(Comment.where(body__like=u'cm12 to p12').all()) # cm12
log(Comment.where(body__like='%cm12%').all()) # cm12
log(Comment.where(body__ilike='%CM12%').all()) # cm12
log(Comment.where(body__startswith='cm1').all()) # cm11, cm12
log(Comment.where(body__istartswith='CM1').all()) # cm11, cm12
log(Comment.where(body__endswith='to p12').all()) # cm12
log(Comment.where(body__iendswith='TO P12').all()) # cm12
# dates
# year
log(Comment.where(created_at__year=2014).all()) # cm11
log(Comment.where(created_at__year=2015).all()) # cm12, cm21
# month
log(Comment.where(created_at__month=1).all()) # cm11
log(Comment.where(created_at__month=11).all()) # cm21, cm22
# day
log(Comment.where(created_at__day=1).all()) # cm11
log(Comment.where(created_at__day=20).all()) # cm12, cm22
# whole date
log(Comment.where(created_at__year=2014, created_at__month=1,
created_at__day=1).all()) # cm11
# date comparisons
log(Comment.where(created_at__year_gt=2014).all()) # cm12, cm21, cm22
##### 1.4 where() with auto-joined relations #####
# when have no joins, where() is a shortcut for filter_expr
log(session.query(Comment).filter(
*Comment.filter_expr(rating__gt=2, body__startswith='cm1')).all())
log(Comment.where(rating__gt=2, body__startswith='cm1').all())
# but where() can automatically join relations
# users having posts which are commented by user 2
log(User.where(posts___comments___user_id=u2.id).all())
# comments where user name starts with 'Bi'
# !! ATTENTION !!
# about Comment.post:
# although we have Post.comments relationship,
# it's important to **add relationship Comment.post** too,
# not just use backref !!!
log(Comment.where(user___name__startswith='Bi').all())
# non-public posts commented by user 1
log(Post.where(public=False, is_commented_by_user=u1).all())
#### 2. sort ####
#### 2.1 simple demo ####
##### 2.1.1 low-level order_expr()
# '-rating', 'created_at' means 'ORDER BY rating DESC, created_at ASC'
log(session.query(Comment).order_by(
*Comment.order_expr('-rating', 'created_at')).all())
##### 2.1.2 high-level sort()
log(Comment.sort('-rating', 'created_at'))
# in real world apps, you will keep attrs in list
sort_attrs = ['-rating', 'created_at']
log(Comment.sort(*sort_attrs))
##### 2.1.3 hybrid properties
log(session.query(Post).order_by(*Post.order_expr('-public')).all())
log(Post.sort('-public').all())
#### 2.2 sort() with auto-joined relations ####
# sort by name of user ASC (user relation will be auto-joined), then by
# created_at DESC
log(Comment.sort('user___name', '-created_at').all())
# get comments on public posts first, then order by post user name
# Post and User tables will be auto-joined
log(Comment.sort('-post___public', 'post___user___name').all())
#### 3. smart_query() : combination of where(), sort() and eager load ####
schema = {
Comment.post: {
Post.user: JOINED
}
}
##### 3.1 high-level smart_query() class method #####
res = Comment.smart_query(
filters={
'post___public': True,
'user__isnull': False
},
sort_attrs=['user___name', '-created_at'],
schema=schema).all()
log(res) # cm12, cm21, cm22
##### 3.2 more flexible smart_query() function #####
##### 3.2.1. The same as 3.1
query = Comment.query # could be any query you want
res = smart_query(query,
filters={
'post___public': True,
'user__isnull': False
},
sort_attrs=['user___name', '-created_at'],
schema=schema).all()
log(res) # cm12, cm21, cm22
##### 3.2.2. Real-life example with lazy='dynamic' relationship
# let's imagine we want to display some user relations
# and flexibly filter, sort and eagerload them
# like this http://www.qopy.me/LwfSCu_ETM6At6el8wlbYA
# (no sort on screenshot, but you've git the idea)
# so we have a user
user = session.query(User).first()
# and we have initial query for his/her comments
# (see User.comments_ relationship)
query = user.comments_
# now we just smartly apply all filters, sorts and eagerload. Perfect!
res = smart_query(query,
filters={
'post___public': True,
'user__isnull': False
},
sort_attrs=['user___name', '-created_at'],
schema=schema).all()
log(res) # cm21
##### 3.2.3 Logical operators and arbitrary expressions in filters
# If we want to use OR, NOT or other logical operators in our queries
# we can nest the filters dictionary:
res = Post.smart_query(filters={
sa.or_: {'archived': True, 'is_commented_by_user': u3}
})
log(res) # p11, p22
# Some logic cannot be expressed without using a list instead, e.g.
# (X OR Y) AND (W OR Z)
# E.g. (somewhat contrived example):
# (non-archived OR has comments) AND
# (user_name like 'B%' or user_name like 'C%')
res = Post.smart_query(filters=[
{sa.or_: {'archived': False, 'comments__isnull': False }},
{sa.or_: [
{'user___name__like': 'B%'},
{'user___name__like': 'C%'}
]}
])
# !! NOTE !! This cannot be used with the where method, e.g.
# Post.where(**{sa.or: {...}})
# TypeError!! (only strings are allowed as keyword arguments)
# Tested with sa.or_, sa.and_ and sa._not. Other functions that
# return a sqla expression should also work
##### 3.3 auto eager load in where() and sort() with auto-joined relations ####
"""
Smart_query does auto-joins for filtering/sorting,
so there's a sense to tell sqlalchemy that we alreeady joined that relation
So we test that relations are set to be joinedload
if they were used in smart_query()
"""
##### 3.3.1 where()
# comments on public posts where posted user name like ...
res = Comment.where(post___public=True, post___user___name__like='Bi%').all()
log(res)
# no additional query needed: we used 'post' and 'post__user'
# relations in smart_query()
log(res[0].post)
log(res[0].post.user)
# we didn't use post___comments in filters, so additional query is needed
log(res[0].post.comments)
##### 3.3.2 sort()
res = Comment.sort('-post___public', 'post___user___name').all()
log(res)
# no additional query needed: we used 'post' and 'post__user'
# relations in smart_query()
log(res[0].post)
log(res[0].post.user)
# we didn't use post___comments in filters, so additional query is needed
log(res[0].post.comments)