DataError: (psycopg2.DataError) invalid input syntax for integer

I'm trying to add Flask-Login to my Flask-Python app but I'm having this error and I don't know why. I guess thats my user.loader that isnt correct but the idea is to load the user based on the ID or email.

What am I doing wrong?

full error:

DataError: (psycopg2.DataError) invalid input syntax for integer:
"[email protected]" LINE 3: WHERE users.uid = '[email protected]'

app.py

from flask import Flask, render_template, request, session, redirect, url_for
from models import db, User
from forms import SignupForm, LoginForm
from flask_login import LoginManager, UserMixin, \
                                login_required, login_user, logout_user

app = Flask(__name__)

app.config['SQLALCHEMY_DATABASE_URI'] = 'postgresql://localhost/polex'
db.init_app(app)

login_manager = LoginManager()
login_manager.init_app(app)
login_manager.login_view = "login"

app.secret_key = "development-key"


@login_manager.user_loader
def user_loader(uid):
    """Given *user_id*, return the associated User object.

    :param unicode user_id: user_id (email) user to retrieve
    """
    return User.query.get(uid)


@app.route("/")
def index():
  return render_template("index.html")

@app.route("/about")
def about():
  return render_template("about.html")

@app.route("/signup", methods=["GET", "POST"])
def signup():
  if 'email' in session:
    return redirect(url_for('home'))

  form = SignupForm()

  if request.method == "POST":
    if form.validate() == False:
      return render_template('signup.html', form=form)
    else:
      newuser = User(form.first_name.data, form.last_name.data, form.email.data, form.password.data)
      db.session.add(newuser)
      db.session.commit()

      session['email'] = newuser.email
      return redirect(url_for('home'))

  elif request.method == "GET":
    return render_template('signup.html', form=form)

@app.route("/login", methods=["GET", "POST"])
def login():
  print db
  
  form = LoginForm()

  if request.method == "POST":
    if form.validate() == False:
      return render_template("login.html", form=form)
    else:
      email = form.email.data 
      password = form.password.data 

      user = User.query.filter_by(email=email).first()
      if user is not None and user.check_password(password):
        login_user(user, remember=True) 
        return redirect(url_for('home'))
      else:
        return redirect(url_for('login'))

  elif request.method == 'GET':
    return render_template('login.html', form=form)

@app.route("/logout")
def logout():
  session.pop('email', None)
  return redirect(url_for('index'))

@app.route("/home", methods=["GET", "POST"])

def home():
  

  return render_template("home.html")

if __name__ == "__main__":
  app.run(debug=True)

models.py

from flask_sqlalchemy import SQLAlchemy
from werkzeug import generate_password_hash, check_password_hash
from flask_login import UserMixin

db = SQLAlchemy()

class User(db.Model):
  __tablename__ = 'users'
  uid = db.Column(db.Integer, primary_key = True)
  firstname = db.Column(db.String(100))
  lastname = db.Column(db.String(100))
  email = db.Column(db.String(120), unique=True)
  pwdhash = db.Column(db.String(54))

  #-----login requirements-----
  def is_active(self):
    #all users are active
    return True 

  def get_id(self):
        # returns the user e-mail. not sure who calls this
    return self.email

  def is_authenticated(self):
    return self.authenticated

  def is_anonymous(self):
        # False as we do not support annonymity
    return False

  def __init__(self, firstname, lastname, email, password):
    self.firstname = firstname.title()
    self.lastname = lastname.title()
    self.email = email.lower()
    self.set_password(password)
     
  def set_password(self, password):
    self.pwdhash = generate_password_hash(password)

  def check_password(self, password):
    return check_password_hash(self.pwdhash, password)