[Sqlalchemy-tickets] Issue #3169: _fetch_implicit_returning raises TypeError if INSERT FROM SELECT inserts no rows (zzzeek/sqlalchemy)

[Richard F. <iss...@bi...>]

New issue 3169: _fetch_implicit_returning raises TypeError if INSERT FROM SELECT inserts no rows
https://bitbucket.org/zzzeek/sqlalchemy/issue/3169/_fetch_implicit_returning-raises-typeerror

Richard Frank:

I'm inserting into a table using the results of a query.  When that query returns no rows, a TypeError is raised.  A test example:

```
#!python

from sqlalchemy import create_engine, String, Column, Table, MetaData, \
    literal_column, select

engine = create_engine('postgresql://rich@localhost/test', echo=True)

metadata = MetaData()

with engine.connect() as conn:

    tbl = Table('test_table', metadata, Column('id', String, primary_key=True))
    tbl.create(bind=conn)

    conn.execute(
        tbl.insert()
        .from_select(
            [tbl.c.id],
            select([literal_column("'id'")])
            .where(literal_column("false")))
    )

```
dies with the following error on 0.9.7 with psycopg2 2.5.3 and postgresql 9.3.4:
```
#!python

2014-08-20 17:34:19,054 INFO sqlalchemy.engine.base.Engine select version()
2014-08-20 17:34:19,054 INFO sqlalchemy.engine.base.Engine {}
2014-08-20 17:34:19,057 INFO sqlalchemy.engine.base.Engine select current_schema()
2014-08-20 17:34:19,057 INFO sqlalchemy.engine.base.Engine {}
2014-08-20 17:34:19,058 INFO sqlalchemy.engine.base.Engine SELECT CAST('test plain returns' AS VARCHAR(60)) AS anon_1
2014-08-20 17:34:19,058 INFO sqlalchemy.engine.base.Engine {}
2014-08-20 17:34:19,059 INFO sqlalchemy.engine.base.Engine SELECT CAST('test unicode returns' AS VARCHAR(60)) AS anon_1
2014-08-20 17:34:19,059 INFO sqlalchemy.engine.base.Engine {}
2014-08-20 17:34:19,060 INFO sqlalchemy.engine.base.Engine show standard_conforming_strings
2014-08-20 17:34:19,060 INFO sqlalchemy.engine.base.Engine {}
2014-08-20 17:34:19,062 INFO sqlalchemy.engine.base.Engine 
CREATE TABLE test_table (
	id VARCHAR NOT NULL, 
	PRIMARY KEY (id)
)


2014-08-20 17:34:19,062 INFO sqlalchemy.engine.base.Engine {}
2014-08-20 17:34:19,069 INFO sqlalchemy.engine.base.Engine COMMIT
2014-08-20 17:34:19,071 INFO sqlalchemy.engine.base.Engine INSERT INTO test_table (id) SELECT 'id' 
WHERE false RETURNING test_table.id
2014-08-20 17:34:19,071 INFO sqlalchemy.engine.base.Engine {}
Traceback (most recent call last):
  File "test.py", line 19, in <module>
    .where(literal_column("false")))
  File "/Users/rich/.virtualenvs/test/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 729, in execute
    return meth(self, multiparams, params)
  File "/Users/rich/.virtualenvs/test/lib/python2.7/site-packages/sqlalchemy/sql/elements.py", line 321, in _execute_on_connection
    return connection._execute_clauseelement(self, multiparams, params)
  File "/Users/rich/.virtualenvs/test/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 826, in _execute_clauseelement
    compiled_sql, distilled_params
  File "/Users/rich/.virtualenvs/test/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 978, in _execute_context
    context._fetch_implicit_returning(result)
  File "/Users/rich/.virtualenvs/test/lib/python2.7/site-packages/sqlalchemy/engine/default.py", line 815, in _fetch_implicit_returning
    ipk.append(row[c])
TypeError: 'NoneType' object has no attribute '__getitem__'
```

Assuming that functionality isn't needed, looks like this can be worked around by setting ```implicit_returning=False``` on the engine or table.