Here's the code I have in my models.py file, sitting at the very bottom, as per this guide:
db.configure_mappers()
db.create_all()
db.commit()
This will execute at import time. So now, whenever I import a model, I get the following message:
RuntimeError: application not registered on db instance and no applicationbound to current context
I'm not sure how to factor this code into the factory paradigm. I tried to wrap the code in a function, and then call it in create_app.
When I do that, this is the error I get:
sqlalchemy.exc.CompileError: (in table 'ad', column 'search_vector'): Compiler <sqlalchemy.dialects.sqlite.base.SQLiteTypeCompiler object at 0x7f81bfc14940> can't render element of type <class 'sqlalchemy.dialects.postgresql.base.TSVECTOR'>
The search_vector column is pretty simple, taken from the sqlalchemy-searchable quickstart guide:
search_vector = db.Column(TSVectorType('title', 'body'))
Your approach is correct — wrap initializing code in a function:
from models import db
def create_app():
app = Flask(__name__)
db.init_app(app)
db.configure_mappers()
db.create_all()
db.commit()
return app
app = create_app()
Or if you want to avoid cluttering your launch file define the function taking application as parameter (models.py):
def init_db(app):
db.init_app(app)
db.configure_mappers()
db.create_all()
db.commit()
And use the function to initialize application:
from models import init_db
app = Flask(__name__)
init_db(app)
But your error is caused by another problem: SQLite does not support TSVector, it is PostgreSQL specific feature. All examples for SQAlchemy-Searchable are written for PostgreSQL databases.
It also looks like SQLite does not have full text search out of the box. Perhaps you need to switch to another DBMS.
Related
I'd like to use Flask's application factory mechanism fpr my application. I have is that the databases I use within some blueprints are located differently, so I'm using binds for pointing to them. The tables itself are in production and already in use, so I need to reflect them in order to use them within my application.
Problem is that I can't get the reflect function working because of the application context. I always get the message, that I'm working outside the application context. I fully understand that and see, that db is really outside, but don't have any idea anymore on how to involve it.
I tried different variations on passing app via current_app to my models.py, but nothing was working.
config.py:
class Config(object):
#Secret key
SECRET_KEY = 'my_very_secret_key'
ITEMS_PER_PAGE = 25
SQLALCHEMY_BINDS = {
'mysql_bind': 'mysql+mysqlconnector://localhost:3306/tmpdb'
}
SQLALCHEMY_TRACK_MODIFICATIONS = False
main.py:
from webapp import create_app
app = create_app('config.Config')
if __name__ == '__main__':
app.run(debug=true)
webapp/init.py:
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
db = SQLAlchemy()
def create_app(config_object):
app=Flask(__name__)
app.config.from_object(config_object)
db.init_app(app)
from main import create_module as main_create_module
main_create_module(app)
return app
webapp/main/init.py:
def create_module(app):
from .controller import blueprint
app.register(blueprint)
webapp/main/controller.py:
from flask import Blueprint, render_template, current_app as app
from .models import db, MyTable # <-- Problem might be here ...
bluerint = Blueprint('main', __name__)
#blueprint.route('/'):
def index():
resp = db.session.query(MyTable)\
.db.func.count(MyTable.versions)\
.filter(MyTable.versions =! '')\
.group_by(MyTable.name).all()
if resp:
return render_template('index.html', respo=respo)
else:
return 'Nothing happend'
webapp/main/models.py:
from .. import db # <-- and here ...
db.reflect(bind='mysql_bind')
class MyTable(db.Model):
__bind_key__ = 'mysql_bind'
__table__ = db.metadata.tables['my_table']
Expected result would be to get the reflection working in different blueprints.
Got it working, full solution here:
https://github.com/researcher2/stackoverflow_56885380
I have used sqllite3 for the test, run create_db.py script to setup db. Run flask with debug.sh, since recent versions you can't seem to just app.run() inside __main__ anymore.
Explanation
As I understand it a blueprint is just a way to group together several views if you need to use them multiple times in a single app or across multiple apps. You can add different route prefix as you desire.
A db object is not associated with a blueprint, it is associated with an app, which provide the configuration information. Once inside the blueprint views you will have access to the db object with the relevant app context automatically available.
Regarding the db.reflect, you need to make the call inside create_app and pass it the app object(preferred) or import the app inside the model which is spaghetti.
Multiple DBs can be accessed using binding as you've shown.
So your blueprints will have access to all tables imported and flask-sqlalchemy knows which db connection to use based on the binding.
I'm normally a fan of explicitly defining tables so you have access to the ORM objects and fields in code completion. Do you have lots of tables/fields or maybe you are creating something to query table metadata for total automation on any schema? Like a schema viewer or something like that.
This might be useful for others coming to this post:
https://flask-sqlalchemy.palletsprojects.com/en/2.x/contexts/
Brilliant! Thank you very much. Got it also working. Your tip gave me a hint to find another way:
#blueprint.route('/')
def index():
# pushing app_context() to import MyTable
# now I can use db.reflect() also in models.py
with app.app_context():
from .models import MyTable
results = db.session.query(MyTable).all()
print(results)
for row in results:
print (row)
print(row.versions)
print(row.name)
if results:
return render_template('my_table.html', results=results)
else:
return 'Nothing happend'
Then the reflection can be done inside models.py. The link you posted is really helpful, don't know why I did not stumble over it myself ...
Anyway, I do now have a lot more possibilities than before!
Cheers, mate!
I have a working sample Flask-Admin application on GitHub which queries a view (itself based on MySQL's information_schema.TABLES) in order to dynamically update a ModelView's column_labels and column_descriptions properties. There's also a small template modification to add tooltips to the header row containing the column comments from the database.
I put a lot of effort into figuring this out because it seemed foolish to re-type column descriptions in my Python code when they had already been entered into the database using the COMMENT SQL keyword during table creation.
In the simple test app, everything works as expected; I receive the model and session parameters given to the ModelView's __init__ method, and I use the session to query the other model for the column labels / comments, update self.column_labels and self.column_descriptions on the view, then call super().
However, in a more complicated app, I get the dreaded RuntimeError: No application found. Either work inside a view function or push an application context when I try to query the other model within a ModelView's __init__ method. The only marked difference I would note between the demo app and my "real" app is that I import a SQLAlchemy object instantiated in another .py file and then invoke its init_app() in my app.py to wire it up to the Flask instance.
Edit: which is exactly what the problem is; SQLAlchemy instances created using in the usual way, demonstrated in the Flask-SQLAlchemy Quickstart get a proper Flask application instance in their __init__()s; when I use db.init_app(app), I get the No application found error instead.
My question is: at which point does a Flask-Admin ModelView start existing inside a Flask application context? Why are circumstances different for import db from somewhere.py; db.init_app(app) vs. db = SQLAlchemy(app)? Is there any way that I can trace the start-up process of a Flask application and hook into that exact moment so I can see what's going on here?
Here are the two basic parts that are involved (complete source for each is on GitHub, as noted above):
The model that provides the column "metadata," including comments
# models.py
# [SQLALchemy imports and declaration of 'Base']
class ColumnProperty(Base):
# this view is based on MySQL's 'information_schema.TABLES'
__tablename__ = 'v_column_properties'
parent_table = Column(String(64), primary_key=True)
name = Column(String(64), primary_key=True)
# [some fields elided]
comment = Column(String(1024)) # type: str
and
The ModelView which queries the above model upon instantiation
# views.py
from flask_admin.contrib.sqla import ModelView
class TestView(ModelView):
def __init__(self, model, session, **kwargs):
from models import ColumnProperty as cp
descriptions = {}
q = session.query(cp).filter(cp.parent_table==model.__tablename__)
for row in q.all():
descriptions[row.name] = row.comment
self.column_descriptions = descriptions
super(TestView, self).__init__(model, session, **kwargs)
I would override the render method of ModelView and set your column_descriptions there. Obviously you could setup some kind of caching mechanism to reduce the number of database queries.
Something like (completely untested) - note use of self.session in querying:
# views.py
from flask_admin.contrib.sqla import ModelView
class TestView(ModelView):
def render(self, template, **kwargs):
from models import ColumnProperty as cp
descriptions = {}
q = self.session.query(cp).filter(cp.parent_table==model.__tablename__)
for row in q.all():
descriptions[row.name] = row.comment
self.column_descriptions = descriptions
super(TestView, self).render(template, **kwargs)
I realize I'm a bit late to the show but since I had a similar problem I'll share my findings.
It seems that in order to get an application context for the ModelView you have to initialize it within with app.app_context(), like this, in case of your app.py:
...
#app.py
with app.app_context():
admin = Admin(app, name="{}-admin".format(cfg['database']),
index_view=AdminIndexView(name='Admin Home', url='/'),
template_mode='bootstrap3')
admin.add_view(TestView(Test, db.session))
admin.add_view(ColumnPropertiesView(ColumnProperty, db.session))
...
In you prefer using an application factory pattern, you could do something along these lines:
#app.py
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_admin import Admin, AdminIndexView
db = SQLAlchemy()
def create_app():
"""The application factory"""
app = Flask(__name__)
app.config.from_object('app.config')
db.init_app(app)
with app.app_context():
admin = Admin(app, name="{}-admin".format(cfg['database']),
index_view=AdminIndexView(name='Admin Home', url='/'),
template_mode='bootstrap3')
from models import Test, ColumnProperty
from views import TestView, ColumnPropertiesView
admin.add_view(TestView(Test, db.session))
admin.add_view(ColumnPropertiesView(ColumnProperty, db.session))
return app
I'm trying to test my flask application using unittest. I want to refrain from flask-testing because I don't like to get ahead of myself.
I've really been struggling with this unittest thing now. It is confusing because there's the request context and the app context and I don't know which one I need to be in when I call db.create_all().
It seems like when I do add to the database, it adds my models to the database specified in my app module (init.py) file, but not the database specified in the setUp(self) method.
I have some methods that must populate the database before every test_ method.
How can I point my db to the right path?
def setUp(self):
#self.db_gd, app.config['DATABASE'] = tempfile.mkstemp()
app.config['TESTING'] = True
# app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///' + app.config['DATABASE']
basedir = os.path.abspath(os.path.dirname(__file__))
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///' + \
os.path.join(basedir, 'test.db')
db = SQLAlchemy(app)
db.create_all()
#self.app = app.test_client()
#self.app.testing = True
self.create_roles()
self.create_users()
self.create_buildings()
#with app.app_context():
# db.create_all()
# self.create_roles()
# self.create_users()
# self.create_buildings()
def tearDown(self):
#with app.app_context():
#with app.request_context():
db.session.remove()
db.drop_all()
#os.close(self.db_gd)
#os.unlink(app.config['DATABASE'])
Here is one of the methods that populates my database:
def create_users(self):
#raise ValueError(User.query.all())
new_user = User('Some User Name','xxxxx#gmail.com','admin')
new_user.role_id = 1
new_user.status = 1
new_user.password = generate_password_hash(new_user.password)
db.session.add(new_user)
Places I've looked at:
http://kronosapiens.github.io/blog/2014/08/14/understanding-contexts-in-flask.html
http://blog.miguelgrinberg.com/post/the-flask-mega-tutorial-part-xvi-debugging-testing-and-profiling
And the flask documentation:
http://flask.pocoo.org/docs/0.10/testing/
one issue that your hitting is the limitations of flask contexts, this is the primary reason i think long and hard before including a flask extension into my project, and flask-sqlalchemy is one of the biggest offenders. i say this because in most cases it is completely unnecessary to depend on the flask app context when dealing with your database. Sure it can be nice, especially since flask-sqlalchemy does a lot behind the scenes for you, mainly you dont have to manually manage your session, metadata or engine, but keeping that in mind those things can easily be done on your own, and for doing that you get the benefit of unrestricted access to your database, with no worry about the flask context. here is an example of how to setup your db manually, first i will show the flask-sqlalchemy way, then the manual plain sqlalchemy way:
the flask-sqlalchemy way:
import flask
from flask_sqlalchemy import SQLAlchemy
app = flask.Flask(__name__)
db = SQLAlchemy(app)
# define your models using db.Model as base class
# and define columns using classes inside of db
# ie: db.Column(db.String(255),nullable=False)
# then create database
db.create_all() # <-- gives error if not currently running flask app
the standard sqlalchemy way:
import flask
import sqlalchemy as sa
from sqlalchemy.ext.declarative import declarative_base
# first we need our database engine for the connection
engine = sa.create_engine(MY_DB_URL,echo=True)
# the line above is part of the benefit of using flask-sqlalchemy,
# it passes your database uri to this function using the config value
# SQLALCHEMY_DATABASE_URI, but that config value is one reason we are
# tied to the application context
# now we need our session to create querys with
Session = sa.orm.scoped_session(sa.orm.sessionmaker())
Session.configure(bind=engine)
session = Session()
# now we need a base class for our models to inherit from
Model = declarative_base()
# and we need to tie the engine to our base class
Model.metadata.bind = engine
# now define your models using Model as base class and
# anything that would have come from db, ie: db.Column
# will be in sa, ie: sa.Column
# then when your ready, to create your db just call
Model.metadata.create_all()
# no flask context management needed now
if you set your app up like that, any context issues your having should go away.
as a separate answer, to actually just force what you need to work, you can just use the test_request_context function, ie: in setup do: self.ctx = app.test_request_context() then just activate it, self.ctx.push() and when your done get rid of it, ie in tearDown: self.ctx.pop()
I am trying to separate some of my database logic into its own helper module. This is because I have several routes that perform the same database functions, and I don't want to keep repeating the same code. I'm a bit confused on the db session scopes.
From the SQLAlchemy docs:
Some web frameworks include infrastructure to assist in the task of aligning the lifespan of a Session with that of a web request. This includes products such as Flask-SQLAlchemy, for usage in conjunction with the Flask web framework...
I think this means my db session scope is contained within a particular route since I'm using Flask and Flask-SQLAlchemy, so I came up with the following:
init.py
app = Flask(__name__)
db = SQLAlchemy(app)
routes.py
from init import db
#app.route('/one')
def one():
form = MyForm()
if form.validate_on_submit():
myhelper.saveStuff1(form.stuff1.data)
myhelper.saveStuff2(form.stuff2.data)
db.session.commit()
return render_template(...)
#app.route('/two')
def two():
form = MyForm()
if form.validate_on_submit():
myhelper.saveStuff1(form.stuff1.data)
myhelper.saveStuff2(form.stuff2.data)
myhelper.saveStuff3(form.stuff3.data)
db.session.commit()
return render_template(...)
myhelper.py
from init import db
# Add new Item
def saveStuff1(formdata):
db.session.add(Item(name=formdata))
# Update Item
def saveStuff2(formdata):
item = Item.query.filter_by(name=formdata).first()
item.description = 'default'
db.session.add(item)
# etc...
Would this be the correct way for structuring my helpers? I'm worried that from init import db will cause problems with scoping since it's imported in both files, or if this overall code pattern will cause other problems.
SQLAlchemy's session scope is not related to Python's variable scope. So no, importing db in multiple places as you've shown won't cause problems. Regarding the session scope, Flask-SQLAlchemy takes care of that for you, so you can ignore (or not worry about) the discussion of scope in the SQLAlchemy docs.
I am building my first app with Flask Python micro-framework and I have a problem with committing my models to the database. When I test my User model on the command line, all works well. But when I do a db.session.commit(), I have error 1146 : "Table doesn't exist."
I'm using a MySQL database in local mode and there is no error with login/password
Maybe I'm doing it wrong on the configuration or something else. So here is my config application config file
from flask import Flask
from flask.ext.sqlalchemy import SQLAlchemy
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql://root:admin#localhost/flask_db'
db = SQLAlchemy(app)
from app import views
The error explains it all-- while you may have the models for your data, you haven't yet created the tables in the database to store and query them. Simply import your models then run db.create_all() to generate the tables and you should be good to go.
It'll be worth you reading the quickstart guide for Flask-SQLAlchemy to get your head around the general flow.