Single Custom Filter Requiring Joins

gist.py

import os
import os.path as op
from flask import Flask
from flask.ext.sqlalchemy import SQLAlchemy

from flask.ext import admin
from flask.ext.admin.contrib import sqla
from flask.ext.admin.contrib.sqla import filters


# Create application
app = Flask(__name__)

# Create dummy secrey key so we can use sessions
app.config['SECRET_KEY'] = '123456790'

# Create in-memory database
app.config['DATABASE_FILE'] = 'sample_db.sqlite'
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///' + app.config['DATABASE_FILE']
app.config['SQLALCHEMY_ECHO'] = True
db = SQLAlchemy(app)

class Model1(db.Model):
    def __init__(self, test1=None):
        self.test1 = test1

    id = db.Column(db.Integer, primary_key=True)
    test1 = db.Column(db.String(20))
    
    def __unicode__(self):
        return self.test1

    def __str__(self):
        return self.test1

class Model2(db.Model):
    def __init__(self, string_field=None):
        self.string_field = string_field

    id = db.Column(db.Integer, primary_key=True)
    string_field = db.Column(db.String)

    # Relation
    model1_id = db.Column(db.Integer, db.ForeignKey(Model1.id))
    model1 = db.relationship(Model1, backref='model2')
    
# Flask views
@app.route('/')
def index():
    return '<a href="/admin/">Click me to get to Admin!</a>'

# Customized User model admin
class Model2View(sqla.ModelView):
    column_filters = [
        #'model1.test1' #uncomment to fix
        filters.FilterEqual(Model1.test1, "Test1"),
    ]

# Create admin
admin = admin.Admin(app, name='Example: SQLAlchemy')

# Add views
admin.add_view(Model2View(Model2, db.session))

def build_sample_db():
    db.drop_all()
    db.create_all()

    # Create parent/child values
    for count in range(1, 5):
        model2_obj = Model2("model2_val" + str(count))
        model2_obj.model1 = Model1("model1_val" + str(count))
        db.session.add(model2_obj)
        
    db.session.commit()

if __name__ == '__main__':
    # Build a sample db on the fly, if one does not exist yet.
    app_dir = op.realpath(os.path.dirname(__file__))
    database_path = op.join(app_dir, app.config['DATABASE_FILE'])
    if not os.path.exists(database_path):
        build_sample_db()

    # Start app
    app.run(debug=True, host="0.0.0.0", port=5090)