Handling same-named columns in dbt server

[jtcohen6]

Describe the bug

run_sql for queries that include two columns of the same name has surprising results.

Steps To Reproduce

Query: select 'one' as column_a, 'two' as column_a

dbt Cloud IDE

dbt rpc

{
    "jsonrpc": "2.0",
    "method": "run_sql",
    "id": "2db9a2fe-9a39-41ef-828c-25e04dd6b07d",
    "params": {
        "timeout": 60,
        "sql": "c2VsZWN0ICdvbmUnIGFzIGNvbHVtbl9hLCAndHdvJyBhcyBjb2x1bW5fYQ==",
        "name": "my_first_query"
    }
}

...
               "table": {
                    "column_names": [
                        "column_a",
                        "column_a_2"
                    ],
                    "rows": [
                        [
                            "two",
                            null
                        ]
                    ]
                }
...

Expected behavior

For reference, this is what happens when you run the same query in Snowflake:

I would understand that supporting this result set is not possible/desirable, but I would expect an exception if so, or at least documentation of the limitation.

The output of dbt --version:

$ dbt --version
installed version: 0.17.0
   latest version: 0.17.0

Up to date!

Plugins:
  - bigquery: 0.17.0
  - snowflake: 0.17.0
  - redshift: 0.17.0
  - postgres: 0.17.0

[jtcohen6]

Closing in favor of #3147!