title: SQLAlchemy connection.execute COMMENT ON Postgres not working
body: <p>I have a local postgres database. I am trying to run a simple <a href="https://www.postgresql.org/docs/9.5/static/sql-comment.html" rel="nofollow noreferrer">comment on</a> command with <code>connection.execute</code>. For example,</p>
  
  <pre><code>import sqlalchemy as sa
  db_url = DB_URL
  db_engine = sa.create_engine(db_url)
  conn = db_engine.connect()
  
  conn.execute('create schema test')
  conn.execute('create table test.testing as (select 1 as value)')
  
  conn.execute("comment on table test.testing is 'this is my table'")
  </code></pre>
  
  <p>This actually does create a table <code>test.testing</code> in my local db, but when I run the following:</p>
  
  <pre><code>select * 
  from pg_description
  join pg_class
  on pg_description.objoid = pg_class.oid
  join pg_namespace
  on pg_class.relnamespace = pg_namespace.oid
  where pg_namespace.nspname = 'test'
  and pg_class.relname = 'testing' 
  </code></pre>
  
  <p>No rows are actually returned.</p>