I have created a postgres materialized view following Jeff Windman's methodology from here:
How to make SQLAlchemy custom DDL be emitted after object inserted?
and here:
http://www.jeffwidman.com/blog/847/
The view factory and the model were adapted to the current project, but all functions and classes are virtual copies of the source model. The model was imported into a view and referenced in a template. Regrettably, it is completely ignored by Migrate(Alembic) and does not migrate/upgrade.
user.py
class User(UserMixin, db.Model):
__tablename__ = 'users'
id = db.Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
username = db.Column(db.String(100), unique=True, nullable=False)
password_hash = db.Column(db.String(255), nullable=False)
individual_id = db.Column(UUID(as_uuid=True), db.ForeignKey('individuals.id', ondelete="CASCADE",
onupdate="CASCADE"), nullable=False)
role_id = db.Column(db.SmallInteger, db.ForeignKey('user_roles.id', ondelete='RESTRICT',
onupdate='CASCADE'), unique=False, index=True, nullable=False)
mv_user_individual = db.relationship('User_individual_MV', backref='users', uselist=False,
primaryjoin='User.id==User_individual_MV.id', foreign_keys='User_individual_MV.id')
individual.py
class Individual(db.Model):
__tablename__ = 'individuals'
id = db.Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
first_name = db.Column(db.String(100), unique=False, index=False, nullable=False)
last_name = db.Column(db.String(100), unique=False, index=False, nullable=False)
users = db.relationship('User',
lazy='subquery',
backref=db.backref('individuals', lazy='select'))
mat_view_factory.py
from sqlalchemy.ext import compiler
from sqlalchemy.schema import DDLElement, PrimaryKeyConstraint
from app import db
class CreateMaterializedView(DDLElement):
def __init__(self, name, selectable):
self.name = name
self.selectable = selectable
#compiler.compiles(CreateMaterializedView)
def compile(element, compiler, **kw):
# Could use "CREATE OR REPLACE MATERIALIZED VIEW..."
# but I'd rather have noisy errors
return 'CREATE MATERIALIZED VIEW %s AS %s' % (
element.name,
compiler.sql_compiler.process(element.selectable, literal_binds=True),
)
def create_mat_view(name, selectable, metadata=db.metadata):
_mt = db.MetaData() # temp metadata just for initial Table object creation
t = db.Table(name, _mt) # the actual mat view class is bound to db.metadata
for c in selectable.c:
t.append_column(db.Column(c.name, c.type, primary_key=c.primary_key))
if not (any([c.primary_key for c in selectable.c])):
t.append_constraint(PrimaryKeyConstraint(*[c.name for c in selectable.c]))
db.event.listen(
metadata, 'after_create',
CreateMaterializedView(name, selectable)
)
#db.event.listens_for(metadata, 'after_create')
def create_indexes(target, connection, **kw):
for idx in t.indexes:
idx.create(connection)
db.event.listen(
metadata, 'before_drop',
db.DDL('DROP MATERIALIZED VIEW IF EXISTS ' + name)
)
return t
def refresh_mat_view(name, concurrently):
# since session.execute() bypasses autoflush, must manually flush in order
# to include newly-created/modified objects in the refresh
db.session.flush()
_con = 'CONCURRENTLY ' if concurrently else ''
db.session.execute('REFRESH MATERIALIZED VIEW ' + _con + name)
def refresh_all_mat_views(concurrently=True):
'''Refreshes all materialized views. Currently, views are refreshed in
non-deterministic order, so view definitions can't depend on each other.'''
mat_views = db.inspect(db.engine).get_view_names(include='materialized')
for v in mat_views:
refresh_mat_view(v, concurrently)
class MaterializedView(db.Model):
__abstract__ = True
#classmethod
def refresh(cls, concurrently=True):
'''Refreshes the current materialized view'''
refresh_mat_view(cls.__table__.fullname, concurrently)
User_individual_MV.py:
from app import db
from app.mat_view_factory import MaterializedView, create_mat_view
from app.models import User, Individual
class User_individual_MV(MaterializedView):
__table__ = create_mat_view('user_individual_mv',
db.select(
[User.id.label('id'),
User.username.label('username'),
User.role_id.label('role_id'),
Individual.id.label('individual_id'),
Individual.first_name.label('first_name'),
Individual.last_name.label('last_name')
]
).select_from(db.join(User, Individual, isouter=False))
).group_by(Individual.last_name)
)
db.Index('uq_user_individual_mv', User_individual_MV.id, unique=True)
Any advice will be greatly appreciated.
Related
Context: I'm making an auctioning website for which I am using Flask-SQLAlchemy. My tables will need to have a many-to-many relationship (as one artpiece can have many user bids and a user can bid on many artpieces)
My question is: it is possible to add another column to my joining table to contain the id of the user bidding, the id of artpiece that they are bidding on and also how much they bid? Also if yes, how would I include this bid in the table when I add a record to said table?
bid_table = db.Table("bid_table",
db.Column("user_id", db.Integer, db.ForeignKey("user.user_id")),
db.Column("item_id", db.Integer, db.ForeignKey("artpiece.item_id"))
)
class User(db.Model):
user_id = db.Column(db.Integer, unique=True, primary_key=True, nullable=False)
username = db.Column(db.Integer, unique=True, nullable=False)
email = db.Column(db.String(50), unique =True, nullable=False)
password = db.Column(db.String(60), nullable=False)
creation_date = db.Column(db.DateTime, default=str(datetime.datetime.now()))
bids = db.relationship("Artpiece", secondary=bid_table, backref=db.backref("bids", lazy="dynamic"))
class Artpiece(db.Model):
item_id = db.Column(db.Integer, unique=True, primary_key=True, nullable=False)
artist = db.Column(db.String(40), nullable=False)
buyer = db.Column(db.String(40), nullable=False)
end_date = db.Column(db.String(40))
highest_bid = db.Column(db.String(40))
It is possible to do this with SQL Alchemy, but it's very cumbersome in my opinion.
SQLAlchemy uses a concept called an Association Proxy to turn a normal table into an association table. This table can have whatever data fields you want on it, but you have to manually tell SQLAlchemy which columns are foreign keys to the other two tables in question.
This is a good example from the documentation.
In your case, the UserKeyword table is the association proxy table that you want to build for your user/bid scenario.
The special_key column is the arbitrary data you would store like the bid amount.
from sqlalchemy import Column, Integer, String, ForeignKey
from sqlalchemy.ext.associationproxy import association_proxy
from sqlalchemy.orm import backref, declarative_base, relationship
Base = declarative_base()
class User(Base):
__tablename__ = 'user'
id = Column(Integer, primary_key=True)
name = Column(String(64))
# association proxy of "user_keywords" collection
# to "keyword" attribute
keywords = association_proxy('user_keywords', 'keyword')
def __init__(self, name):
self.name = name
class UserKeyword(Base):
__tablename__ = 'user_keyword'
user_id = Column(Integer, ForeignKey('user.id'), primary_key=True)
keyword_id = Column(Integer, ForeignKey('keyword.id'), primary_key=True)
special_key = Column(String(50))
# bidirectional attribute/collection of "user"/"user_keywords"
user = relationship(User,
backref=backref("user_keywords",
cascade="all, delete-orphan")
)
# reference to the "Keyword" object
keyword = relationship("Keyword")
def __init__(self, keyword=None, user=None, special_key=None):
self.user = user
self.keyword = keyword
self.special_key = special_key
class Keyword(Base):
__tablename__ = 'keyword'
id = Column(Integer, primary_key=True)
keyword = Column('keyword', String(64))
def __init__(self, keyword):
self.keyword = keyword
def __repr__(self):
return 'Keyword(%s)' % repr(self.keyword)
Check out the full documentation for instructions on how to access and create this kind of model.
Having used this in a real project, it's not particularly fun and if you can avoid it, I would recommend it.
https://docs.sqlalchemy.org/en/14/orm/extensions/associationproxy.html
I have several classes:
import uuid
from app import db, create_app
from sqlalchemy.sql import func
from sqlalchemy.dialects.postgresql import UUID, ARRAY, JSONB
class Ticket(db.Model):
__tablename__ = 'tickets'
id = db.Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
time = db.Column(db.DateTime, server_default=func.now(), index=True)
proposed_names = db.Column(ARRAY(db.String))
measurements = db.relationship('TempMeasurement', back_populates='ticket')
class BaseMeasurement(object):
id = db.Column(db.Integer, primary_key=True)
#declared_attr
def type_id(self):
return db.Column(db.Integer, db.ForeignKey('optical_data_types.id'))
#declared_attr
def type(self):
return db.relationship('OpticalDataType')
#declared_attr
def operator_id(self):
return db.Column(db.Integer, db.ForeignKey('operators.id'))
#declared_attr
def operator(self):
return db.relationship('Operator')
#declared_attr
def item_id(self):
return db.Column(db.String, db.ForeignKey('items.serial'))
#declared_attr
def item(self):
return db.relationship('Item')
time = db.Column(db.DateTime, index=True)
instrument = db.Column(db.String)
instrument_sn = db.Column(db.String)
data = db.Column(JSONB)
class TempMeasurement(db.Model, BaseMeasurement):
__tablename__ = 'ticket_data'
id = db.Column(db.Integer, primary_key=True)
ticket_id = db.Column(UUID(as_uuid=True), db.ForeignKey('tickets.id'), index=True)
ticket = db.relationship('Ticket', back_populates='measurements')
original_paths = db.Column(ARRAY(db.String))
What I want/expect is that I can create a Ticket with several child TempMeasurements and commit this to the database. Something like:
app = create_app()
with app.app_context():
ticket = Ticket()
ticket.measurements = [TempMeasurement(...)]
db.session.add(ticket) # <-- error on this line
db.session.commit()
However, I get an obscure error deep in SQLAlchemy:
AttributeError: 'str' object has no attribute '_sa_instance_state'
with a full trace here.
I thought that it might be because the UUID ticket_id column has as_uuid, so I made it simply UUID (implicitly a str), but this did not solve my issue.
The error is too deep in SQLAlchemy for me to understand -- can anyone help?
I'm developing a web app with python and flask. I use Flask, SQLAlchemy and PostgreSQL for development. I have many-to-one related models. By this models one company can have many users but each user can only have one company.
models.py
class Company(ResourceMixin, db.Model):
__tablename__ = 'companies'
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(100), unique=True, index=True,
nullable=False, server_default='')
phone = db.Column(db.String(24))
email = db.Column(db.String(255), index=True)
address = db.Column(db.String(255))
# Relations
users = db.relationship('User', backref='company')
class User(UserMixin, ResourceMixin, db.Model):
__tablename__ = 'users'
id = db.Column(db.Integer, primary_key=True)
# User details
name = db.Column(db.String(50), index=True)
phone = db.Column(db.String(24))
address = db.Column(db.String(255))
email = db.Column(db.String(255), unique=True, index=True, nullable=False,
server_default='')
password = db.Column(db.String(128), nullable=False, server_default='')
# Relations
company_id = db.Column(db.Integer, db.ForeignKey('companies.id',
onupdate='CASCADE',
ondelete='SET NULL'),
index=True)
views.py
app.route('/')
def index():
company = Company.query.get(1)
flash(company.name, company.user_count)
return render_template('index.html')
Error summary: "user_count" attribute is not part of the Company model.
I want to get the number of the users dynamically from Company model. Attribute should count users on each call of the model and serve it on a regular attribute (like company.user_count). I made it by creating a class method and calling it in view function but i want it to make the process automatic without calling method prior to use attribute.
I tried init function like this:
def __init__(self):
self.user_count = len(self.users)
And like this:
def __init__(self):
self.status()
def status(self):
self.user_count = len(self.users)
return True
And like this:
def __init__(self):
self.status()
#classmethod
def status(self):
self.user_count = len(self.users)
return True
all three versions throws same error. How can i overcome the problem.
Thanks a lot!
You can use a property:
class User(Base):
...
#property
def user_count(self):
return len(self.users)
Below I have a Flask-SQLAlchemy model for the table User.
class User(db.Model):
__tablename__ = 'user'
user_id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(30), nullable=False)
created_at = db.Column(db.DateTime, nullable=False, server_default=db.text("CURRENT_TIMESTAMP"))
updated_at = db.Column(db.DateTime, nullable=False, server_default=db.text("CURRENT_TIMESTAMP"))
def __init__(self):
#self.name = name
self.name = None
def add_user(self, name):
self.name = name
Here add_user is a custom method. So if I call the add_user method it should add the name to the User table.
Likewise how do I write custom methods for CRUD operations in that model itself?
You'll probably want to use a classmethod to accomplish this.
class User(db.Model):
__tablename__ = 'user'
user_id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(30), nullable=False)
created_at = db.Column(db.DateTime, nullable=False, server_default=db.text("CURRENT_TIMESTAMP"))
updated_at = db.Column(db.DateTime, nullable=False, server_default=db.text("CURRENT_TIMESTAMP"))
def __init__(self, name):
self.name = name
#classmethod
def create(cls, **kw):
obj = cls(**kw)
db.session.add(obj)
db.session.commit()
This way you can use User.create(name="kumaran") to create a new user that will be committed to the database.
Better yet, it is a great idea to create a mixin for this method and others like it so that the functionality can be easily reused in your other models:
class BaseMixin(object):
#classmethod
def create(cls, **kw):
obj = cls(**kw)
db.session.add(obj)
db.session.commit()
You can then reuse this functionality in your models by using multiple inheritance, like so:
class User(BaseMixin, db.Model):
__tablename__ = 'user'
user_id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(30), nullable=False)
created_at = db.Column(db.DateTime, nullable=False, server_default=db.text("CURRENT_TIMESTAMP"))
updated_at = db.Column(db.DateTime, nullable=False, server_default=db.text("CURRENT_TIMESTAMP"))
def __init__(self, name):
self.name = name
Not sure this is relevant to Flask-SQLAlchemy, but basic SQLAlchemy has examples of creating Mixin classes or augmenting the Base class.
https://docs.sqlalchemy.org/en/13/orm/extensions/declarative/mixins.html
e.g.
from sqlalchemy.ext.declarative import declared_attr
class MyMixin(object):
#declared_attr
def __tablename__(cls):
return cls.__name__.lower()
__table_args__ = {'mysql_engine': 'InnoDB'}
__mapper_args__= {'always_refresh': True}
id = Column(Integer, primary_key=True)
class MyModel(MyMixin, Base):
name = Column(String(1000))
I would accomplish what you're after like this:
class User(db.Model):
__tablename__ = 'user'
user_id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(30), nullable=False)
created_at = db.Column(db.DateTime, nullable=False, server_default=db.text("CURRENT_TIMESTAMP"))
updated_at = db.Column(db.DateTime, nullable=False, server_default=db.text("CURRENT_TIMESTAMP"))
def __init__(self):
#self.name = name
self.name = None
#classmethod
def add_user(cls, session, name):
user = User(name)
session.add(user)
return User
Then in whatever context you're using it in, create a session, call your method, and commit it.
from .user import User
session = Session()
# or if using Flask SQLAlchemy
# session = db.session
User.add_user(session, 'Foo')
session.commit()
From the sqlalchemy docs:
Keep the lifecycle of the session (and usually the transaction) separate and external.
In contrast to one of the other answers, which assumes you are using this model in a Flask app with FlaskSQLAlchemy's global db.session object, parametrizing the session object like this keeps your model code separate from your session management code. This allows it to be used flexibly in many different contexts.
I am trying to do a relationship() with an OUTER JOIN so that it joins the second table if there is something to join it with. I am currently stuck on how to do this though, I cannot seem to figure out the right combination of options(), relationship() and outerjoin().
I have the following tables and I am trying to join AppLike to Application if a row exists with the Application ID AND the artistID (which is provided by the function)
Happy to provide any additional information, I already have one of my joins working as you can see below, but there will always be a row to match for that one.
from sqlalchemy import Column
from . import Base
from . import DBSession
from sqlalchemy.dialects.mysql import (
INTEGER,
VARCHAR,
TEXT,
TINYINT,
)
from sqlalchemy.sql import and_
from sqlalchemy import ForeignKey
from sqlalchemy.orm import relationship, joinedload
import time
# 0 = new
# 1 = Denied
# 2 = Accepted
def getNewApplications(artistID):
query = DBSession.query(Application).\
options(joinedload('pieces')).\
options(joinedload('vote')).\
filter(AppLike.artist_id==artistID).\
filter(Application.approved==0)
#join(AppPiece, Application.app_id==AppPiece.app_id).\
#outerjoin(AppLike, and_(Application.app_id==AppLike.app_id,
# AppLike.artist_id==artistID)).\
import pdb; pdb.set_trace()
return query.all()
class Application(Base):
""" The SQLAlchemy declarative model class for a FileFavorite object. """
__tablename__ = 'applications'
__table_args__ = {
'mysql_engine': 'InnoDB',
'mysql_charset': 'utf8'
}
app_id = Column(INTEGER(11), autoincrement=True, primary_key=True, nullable=False)
name = Column(VARCHAR(64), nullable=False)
nickname = Column(VARCHAR(64), nullable=False)
email = Column(VARCHAR(255), nullable=False)
description = Column(TEXT(), nullable=False)
profile_link = Column(VARCHAR(128), nullable=False)
location = Column(VARCHAR(64), nullable=False)
approved = Column(TINYINT(4), nullable=False)
pieces = relationship("AppPiece", lazy='joined')
vote = relationship("AppLike", lazy='joined')
def __init__(self, name, nickname, email, desc, profileLink,
location, approved):
self.name = name
self.nickname = nickname
self.email = email
self.description = desc
self.profile_link = profileLink
self.location = location
self.approved = approved
class AppPiece(Base):
""" The SQLAlchemy declarative model class for a FileFavorite object. """
__tablename__ = 'app_pieces'
__table_args__ = {
'mysql_engine': 'InnoDB',
'mysql_charset': 'utf8'
}
app_piece_id = Column(INTEGER(11), autoincrement=True, primary_key=True, nullable=False)
app_id = Column(INTEGER(11), ForeignKey('applications.app_id'))
link = Column(VARCHAR(128), nullable=False)
def __init__(self, appID, link):
self.app_id = appID
self.link = link
class AppLike(Base):
""" The SQLAlchemy declarative model class for a FileFavorite object. """
__tablename__ = 'app_likes'
__table_args__ = {
'mysql_engine': 'InnoDB',
'mysql_charset': 'utf8'
}
app_id = Column(INTEGER(11), ForeignKey('applications.app_id'))
artist_id = Column(INTEGER(11), primary_key=True, nullable=False)
vote = Column(TINYINT(4), nullable=False)
def __init__(self, appID, artistID, vote):
self.app_id = appID
self.artist_id = artistID
self.vote = vote
You definitely don't need options(joinedload('pieces')), it is already defined in your models (lazy='joined'). The join condition is the tricky part here and needs to be done using subquery, since we want to filter there as well. So, the final query should look something like this:
# We do the filtering on AppLike in the subquery and later join
# Application to it.
applike_subq = DBSession.query(AppLike).\
filter(AppLike.artist_id == artistID).subquery()
query = DBSession.query(Application).\
outerjoin(applike_subq, Application.vote).\
filter(Application.approved == 0).all()