Add JSON functionality to SQLAlchemy Dialect

[laserkaplan]

In messing around with getting the Trino SQLAlchemy Dialect to work with JSON columns/data, I came across at least a couple of necessary additions:

• a visit_JSON method is needed in the TrinoTypeCompiler class since SQLAlchemy, by default, doesn't support a JSON type (as it is dialect-specific).
• the TrinoDialect class needs both a _json_serializer and _json_deserializer member, which I believe can simply be json.dumps and json.loads, respectively.

Adding those two items allowed me to create tables with a JSON type and write to them all using SQLAlchemy. However, when attempting to read back from the table, I got the following error:

Traceback (most recent call last):
  File "/Users/laserkaplan/PycharmProjects/proxima/proxima_warehouse/pipelines/process_shopify_orders/process.py", line 95, in <module>
    print(session.execute(select(sis_table).limit(10)).all())
  File "/Users/laserkaplan/.pyenv/versions/proxima-3.9.7/lib/python3.9/site-packages/sqlalchemy/engine/result.py", line 1068, in all
    return self._allrows()
  File "/Users/laserkaplan/.pyenv/versions/proxima-3.9.7/lib/python3.9/site-packages/sqlalchemy/engine/result.py", line 403, in _allrows
    made_rows = [make_row(row) for row in rows]
  File "/Users/laserkaplan/.pyenv/versions/proxima-3.9.7/lib/python3.9/site-packages/sqlalchemy/engine/result.py", line 403, in <listcomp>
    made_rows = [make_row(row) for row in rows]
  File "/Users/laserkaplan/.pyenv/versions/proxima-3.9.7/lib/python3.9/site-packages/sqlalchemy/sql/sqltypes.py", line 2693, in process
    return json_deserializer(value)
TypeError: loads() takes 1 positional argument but 2 were given

So something is off with the deserializer, I just haven't had the chance to dig into it further yet.

Does anyone have any suggestions of how to proceed here? Or, if you have more SQLAlchemy JSON experience than I do (which isn't hard to do :) ), do you know if anything else is missing?

[mdesmet]

Hi @laserkaplan, can you make a PR? This way It will be much easier to have a look at your code and get it working.

[hashhar]

Fixed by #214.