I'm using a flask setup from a while and now trying to install Flask-Blogging module on it. Current modules:
- Flask-sqlalchemy with postgres
- Flask-login
- Flask-Blogging (new)
My application.py looks like this:
from flask import Flask
from flask import session
from flask.ext.blogging import SQLAStorage, BloggingEngine
from flask.ext.login import LoginManager
from flask.ext.sqlalchemy import SQLAlchemy
'''
The main application setup. The order of things is important
in this file.
'''
app = Flask(__name__)
app.config.from_object('config.base')
app.config.from_envvar('APP_CONFIG_FILE')
'''
Initialize database
'''
db = SQLAlchemy(app)
'''
Initialize blogger
'''
storage = SQLAStorage(db=db)
blog_engine = BloggingEngine(app, storage)
the last two lines are the only new things I added (other than the imports). Suddenly now I'm getting error about duplicate table names:
sqlalchemy.exc.InvalidRequestError: Table 'customer' is already defined for this MetaData instance. Specify 'extend_existing=True' to redefine options and columns on an existing Table object.
Any ideas what am I doing wrong? I couldn't find much documentation about Flask-Blogging other than:
http://flask-blogging.readthedocs.org/en/latest/
You get this error because in SQLAStorage.__init__ there is this line:
self._metadata.reflect(bind=self._engine)
This will look at your database and create sqlalchemy table things for all the tables currently in your database.
Thus if your database contains a table called 'customer' the line in your code:
storage = SQLAStorage(db=db)
will automatically model an sqlalchemy table called 'customer' for you.
Now... no doubt you have your own database model definitions somewhere, probably in another python module, something like:
class Customer(db.Model):
id = db.Column(db.Integer, primary_key=True)
...
Since this class definition defines a table called 'customer' and since SQLAStorage has already defined a table called 'customer' you get the exception as soon as your class Customer is imported.
Some ways to work around this problem are:
Import your database definition modules before instantiating SQLAStorage
'''
Initialize database
'''
db = SQLAlchemy(app)
import ankit.db_models # import my db models here so SQLAStorage doesn't do it first
'''
Initialize blogger
'''
storage = SQLAStorage(db=db)
blog_engine = BloggingEngine(app, storage)
or
Tell SQLAStorage to use its own metadata
By passing the db param to SQLAStorage.__init__ you are telling it to use your metadata. You can instead just pass the engine parameter and it will create its own metadata.
storage = SQLAStorage(engine=db.engine)
Related
I'm developing an API with Flask and I cannot retrieve queries from a MySQL database I've connected with flask-sqlalchemy (not sqlalchemy alone). This is a pre-existing database downloaded from my client's PHPMyAdmin, so I haven't ran db.create_all(): I simply created the connection string in config.py, then instantiated db = SQLAchemy() and initialized it (db.init_app(app)) in my factory function (i'm using the factory pattern together with blueprints).
I've already checked and my computer is running the mysql process, the login credentials provided are correct and the database exists in my computer. I'm using MariaDB because I run Manjaro Linux.
This is the connection string, located in config.py:
SQLALCHEMY_DATABASE_URI = os.environ.get('DATABASE_URL') or "mariadb+mariadbconnector://dev:dev#localhost/desayunos56"
This is the relevant model. It was created using flask-sqlacodegen and then modified by me to only use the relevant columns within the table. At models.py:
from flask_sqlalchemy import SQLAlchemy
from app import db
# coding: utf-8
t_aus_postmeta = db.Table(
"""
post_id: Order ID
meta_key: Type of value (client name, billing address)
meta_value: Value of meta_key (Name or address itself)
"""
'aus_postmeta',
#db.Column('meta_id', db.BigInteger, nullable=False),
db.Column('post_id', db.BigInteger, nullable=False, server_default=db.FetchedValue()),
db.Column('meta_key', db.String(255, 'utf8mb4_unicode_ci')),
db.Column('meta_value', db.String(collation='utf8mb4_unicode_ci'))
)
And finally, this is the file with the error, views.py. It's a blueprint already registered to __init__.py. I created it only with the intention of checking if I could run queries, but I don't really intend to render anything from Flask:
from flask import render_template
from . import main
from .. import db
from app.models import t_aus_postmeta
#main.route("/", methods=["GET"])
def index():
result = t_aus_postmeta.query_by(post_id=786).first()
This is the error I get: AttributeError: 'Table' object has no attribute 'query_by'
I think it's noteworthy that, although my linter doesn't complain due to unresolved imports, when I use t_aus_postmeta I don't get any method suggestions.
All the questions I've checked are based on using sqlalchemy instead of flask-sqlalchemy. What could be causing this error? At this point, I'm at a loss.
I don't think that's the right way to create your model. Instead you should create it as a class, which will inherit from db.Model, that contains your query_by method.
models.py
class t_aus_postmeta(db.Model):
"""
post_id: Order ID
meta_key: Type of value (client name, billing address)
meta_value: Value of meta_key (Name or address itself)
"""
__tablename__ = 'aus_postmeta'
post_id = db.Column(db.BigInteger(), nullable=False, server_default=db.FetchedValue())
# rest of your columns...
If you do it this way a valid query would look like this:
t_aus_postmeta.query.filter_by('post_id').first()
Notice that this includes tutiplain's suggestion. I think you got your method name wrong. It's just query followed by a filter_by!
I can't find the API reference for the "query_by" method you are using. It seems there is no such method. Perhaps you meant "filter_by" instead?
I'm trying to setup multiple databases with the same model in flask-sqlalchemy
A sample model looks like below
db = flask.ext.sqlalchemy.SQLAlchemy(app)
app.config['SQLALCHEMY_DATABASE_URI'] = 'your_default_schema_db_uri'
app.config['SQLALCHEMY_BINDS'] = {'other_schema': ''mysql+pymysql://'+UNMAE+':'+PASS+'#'+SERVERURL+':3306/'+ DBNAME,'##your_other_db_uri}
class TableA(db.Model):
# This belongs to Default schema, it doesn't need specify __bind_key__
...
class TableB(db.Model) :
# This belongs to other_schema
__bind_key__ = 'other_schema'
...
db.create_all() works fine and creates the tables in their individual schemas.
I was following https://stackoverflow.com/a/34240889/8270017 and wanted to create a single table using:
TableB.__table__.create(db.session.bind, checkfirst=True)
The table gets created in the default bind and not other_schema.
Is there something I'm missing here? How can I fix it so that it gets created in the other schema.
You need to supply the correct engine to the create function. The correct bind can be retrieved in the following way:
from sqlalchemy.orm import object_mapper
TableB.__table__.create(db.session().get_bind(object_mapper(TableB())), checkfirst=True)
For PG at least I do it like this:
class TableB(db.Model):
__table_args__ = {"schema":"schema_name"}
I have a Pyramid application that does CRUD with SQLAlchemy via pyramid_basemodel. All seems to work nicely.
I then pip installed SQLAlchemy-Continuum, to provide history for certain objects. All I did to configure it was make the following alterations to my models.py file:
import sqlalchemy as sa
from sqlalchemy import (event, Column, Index, Integer, Text, String, Date, DateTime, \
Float, ForeignKey, Table, Boolean,)
from sqlalchemy.orm import (relationship, backref, mapper, scoped_session, sessionmaker,)
from pyramid_basemodel import Base, BaseMixin, Session, save
from pyramid_fullauth.models import User
from sqlalchemy_continuum import make_versioned
from colanderalchemy import setup_schema
from zope.sqlalchemy import ZopeTransactionExtension
DBSession = scoped_session(sessionmaker(extension=ZopeTransactionExtension()))
event.listen(mapper, 'mapper_configured', setup_schema)
# Continuum setup
make_versioned()
# FOR EACH VERSIONED MODEL I ADD __versioned__ = {} at the start of each model def. Eg:
class Thing(Base):
__versioned__ = {}
__tablename__ = 'thing'
id = sa.Column(Integer, primary_key=True)
related_id = sa.Column(Integer, ForeignKey('OtherThing.id'))
other_thing = sa.orm.relationship("OtherThing", backref="thing")
description = sa.Column(String(length=100))
a_date = sa.Column(Date)
some_hours = sa.Column(Integer)
b_date = sa.Column(Date)
more_hours = sa.Column(Integer)
sa.orm.configure_mappers()
(Sorry for the slightly redundant imports; I decided to totally follow the Continuum example and import sqlalchemy as sa, and switch to using that notation in the models that I versioned. I may also be doing stupid, monkey-see monkey-do stuff based on a half-understanding of different tutorials.)
This setup allowed me to run alembic revision --autogenerate and produce ModelHistory tables in the database, but when I go to some of the pages that read the now-versioned models, they give the error
sqlalchemy.exc.UnboundExecutionError: This session is not bound to a single Engine or Connection, and no context was provided to locate a binding.
For some reason it reads one model added in the same way, but then trying to update it fails with the same error.
My guess is that I need to configure whatever Continuum uses for a SQLAlchemy session to point to the existing one configured in Pyramid, but I'm not sure. Am I getting warm?
You're generating a session when you call:
DBSession = scoped_session(sessionmaker(extension=ZopeTransactionExtension()))
but not binding it to an engine. Your pyramid template, pyramid_basemodel, is already generating a session for you and binding it to the engine.
Try removing the DBSession and using Session imported from pyramid_basemodel.
FWIW, if anyone these days is looking how to make SQLAlchemy-Continuum work with Pyramid, here's how you do it:
Assuming you have followed the official Pyramid tutorial is the following:
install SQLAlchemy-Continuum
add make_versioned(user_cls=None) to the top of models/__init__.py
add __versioned__ = {} to MyModel class in models/mymodel.py
And that's it!
I've created a repo that has all the needed bits in place: https://github.com/zupo/tutorial/tree/exploration/sqlalchemy-continuum
I tried to create a table in the "app" database, but got this error:
app=# CREATE TABLE users;
ERROR: syntax error at or near ";"
LINE 1: LINE 1: CREATE TABLE users;
^
The columns are defined in models.py which is why I don't create them here.
Do not create the tables in PostgreSQL, SQLAlchemy will create the table (and the columns) for you. All you need to do is create the database, which you have done. To create the tables with Flask-SQLAlchemy:
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
app = Flask(__name__)
db = SQLAlchemy(app)
class User(db.Model):
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String, nullable=False, unique=True)
with app.app_context():
db.create_all()
To address the error (although as stated above you should not do this), it is because that is not a full CREATE TABLE expression. You need to specify zero or more columns for the table.
CREATE TABLE my_table ();
In my case forgot to import my Model class and code
run without any error:).
If you call create_all() on interactive mode please ensure that you import particular Model class.
Note: Every time you make a change on Model class restart ipython.
Imagine that I have one table in my project with some rows in it.
For example:
# -*- coding: utf-8 -*-
import sqlalchemy as sa
from app import db
class Article(db.Model):
__tablename__ = 'article'
id = sa.Column(sa.Integer, primary_key=True, autoincrement=True)
name = sa.Column(sa.Unicode(255))
content = sa.Column(sa.UnicodeText)
I'm using Flask-SQLAlchemy, so db.session is scoped session object.
I saw in https://github.com/zzzeek/sqlalchemy/blob/master/examples/versioned_history/history_meta.py
but i can't understand how to use it with my existing tables and anymore how to start it. (I get ArgumentError: Session event listen on a scoped_session requires that its creation callable is associated with the Session class. error when I pass db.session in versioned_session func)
From versioning I need the following:
1) query for old versions of object
2) query old versions by date range when they changed
3) revert old state to existing object
4) add additional info to history table when version is creating (for example editor user_id, date_edit, remote_ip)
Please, tell me what are the best practicies for my case and if you can add a little working example for it.
You can work around that error by attaching the event handler to the SignallingSession class[1] instead of the created session object:
from flask.ext.sqlalchemy import SignallingSession
from history_meta import versioned_session, Versioned
# Create your Flask app...
versioned_session(SignallingSession)
db = SQLAlchemy(app)
class Article(Versioned, db.Model):
__tablename__ = 'article'
id = sa.Column(sa.Integer, primary_key=True, autoincrement=True)
name = sa.Column(sa.Unicode(255))
content = sa.Column(sa.UnicodeText)
The sample code creates parallel tables with a _history suffix and an additional changed datetime column. Querying for old versions is just a matter of looking in that table.
For managing the extra fields, I would put them on your main table, and they'll automatically be kept track of in the history table.
[1] Note, if you override SQLAlchemy.create_session() to use a different session class, you should adjust the class you pass to versioned_session.
I think the problem is you're running into this bug: https://github.com/mitsuhiko/flask-sqlalchemy/issues/182
One workaround would be to stop using flask-sqlalchemy and configure sqlalchemy yourself.