title: Flask-SQLAlchemy: How to pass parameters to create_engine() such as pool_size?
body: <p>A noob's confused question:</p>
  
  <p>How and where to set pool_size?</p>
  
  <p>I found setting the pool size in docs as:</p>
  
  <pre><code>engine = create_engine('postgresql://me@localhost/mydb',
                         pool_size=20, max_overflow=0)
  </code></pre>
  
  <p>, but is there a way to set pool_size for below snippet too,if yes pleased to know how?</p>
  
  <pre><code>from flask import Flask
  from flask_sqlalchemy import SQLAlchemy
  
  app = Flask(__name__)
  app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql://root:root@localhost/testdb'
  db = SQLAlchemy(app)
  
  
  class User(db.Model):
      id = db.Column(db.Integer, primary_key=True)
      username = db.Column(db.String(80), unique=True, nullable=False)
      email = db.Column(db.String(120), unique=True, nullable=False)
  
      def __repr__(self):
          return '&lt;User %r&gt;' % self.username
      ......
      ......
  </code></pre>
  
  <p>error is as follows:</p>
  
  <pre><code>sqlalchemy.exc.TimeoutError: QueuePool limit of size 10 overflow 10 reached, connection timed out, timeout 30 
  </code></pre>