How to do a proper upsert using sqlalchemy on postgresql? : <p>I would like to do an upsert using the "new" functionality added by postgresql 9.5, using sqlalchemy core. While it is implemented, I'm pretty confused by the syntax, which I can't adapt to my needs.
Here is a sample code of what I would like to be able to do :</p>

<pre><code>from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class User(Base):
__tablename__ = 'test'
a_id = Column('id',Integer, primary_key=True)
a = Column("a",Integer)

engine = create_engine('postgres://name:password@localhost/test')
User().metadata.create_all(engine)
meta = MetaData(engine)
meta.reflect()
table = Table('test', meta, autoload=True)
conn = engine.connect()

from sqlalchemy.dialects.postgresql import insert as psql_insert
stmt = psql_insert(table).values({table.c['id']: bindparam('id'),
          table.c['a']: bindparam('a')})
stmt = stmt.on_conflict_do_update(
    index_elements=[table.c['id']],
    set_={'a': bindparam('a')})
list_of_dictionary = [{'id':1, 'a':1, }, {'id':2, 'a':2,}]
conn.execute(stmt, list_of_dictionary)
</code></pre>

<p>I basicly want to insert a bulk of rows, and if one id is already taken, I want to update it with the value I initinaly wanted to insert.
However sqlalchemy throw me this error :</p>

<pre><code>CompileError: bindparam() name 'a' is reserved for automatic usage in the VALUES or SET clause of this insert/update statement.   Please use a name other than column name when using bindparam() with insert() or update() (for example, 'b_a').
</code></pre>

<p>While it is a known issue (see <a href="https://groups.google.com/forum/#!topic/sqlalchemy/VwiUlF1cz_o" rel="noreferrer">https://groups.google.com/forum/#!topic/sqlalchemy/VwiUlF1cz_o</a>), I didn't found any proper answer that does not require to modify either the keys of list_of_dictionary or the name of your columns.</p>

<p>I want to know if there is a way of constructing stmt in a way to have a consistent behavior that does not depends on whether the keys of the variable list_of_dictionary are the name of the columns of the inserted table (my code works without error in those cases).</p>
