title: SQLAlchemy / Flask / PostgreSQL pool connection
body: <p>After having played for a long time with Django, I'm trying a bit of Flask with SQLAlchemy, and I must say I quite like it. However there is something that I don't get:
  I have a small Flask / SQLAlchemy app that uses PostgreSQL.
  In my <code>__init__.py</code> file I have:</p>
  
  <pre><code>from flask import Flask
  from flask.ext.sqlalchemy import SQLAlchemy
  
  app = Flask(__name__)
  app.config.from_object('settings')
  db = SQLAlchemy(app)
  </code></pre>
  
  <p>I wanted to know:</p>
  
  <ol>
  <li>Is there automatic connection pooling ? Or does every call to Model.query... create a new connection to the database?</li>
  <li>If not, how can I configure it?</li>
  <li>If yes, what are the defaults, how can I modify the values? </li>
  </ol>
  
  <p>Thank you very much for you help !</p>