Separate SQL errors from connection errors during query execution

[yzchang]

Currently, when something (anything?) went wrong during a query execution, the user gets an OperationalError. For instance,

>>> c = pymonetdb.connect("demo", host="localhost", port=50000)
>>> cc = c.cursor()
>>> c.set_autocommit(True)
>>> cc.execute("select * from sys.tables t1, sys.tables t2, sys.tables t3")

# I killed the server during the execution of this query!

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/kutsurak/.cache/pypoetry/virtualenvs/test-pymonetdb-_ivNU08G-py3.8/lib/python3.8/site-packages/pymonetdb/sql/cursors.py", line 165, in execute
    block = self.connection.execute(query)
  File "/home/kutsurak/.cache/pypoetry/virtualenvs/test-pymonetdb-_ivNU08G-py3.8/lib/python3.8/site-packages/pymonetdb/sql/connections.py", line 140, in execute
    return self.command('s' + query + '\n;')
  File "/home/kutsurak/.cache/pypoetry/virtualenvs/test-pymonetdb-_ivNU08G-py3.8/lib/python3.8/site-packages/pymonetdb/sql/connections.py", line 145, in command
    return self.mapi.cmd(command)
  File "/home/kutsurak/.cache/pypoetry/virtualenvs/test-pymonetdb-_ivNU08G-py3.8/lib/python3.8/site-packages/pymonetdb/mapi.py", line 240, in cmd
    response = self._getblock()
  File "/home/kutsurak/.cache/pypoetry/virtualenvs/test-pymonetdb-_ivNU08G-py3.8/lib/python3.8/site-packages/pymonetdb/mapi.py", line 317, in _getblock
    return self._getblock_inet()
  File "/home/kutsurak/.cache/pypoetry/virtualenvs/test-pymonetdb-_ivNU08G-py3.8/lib/python3.8/site-packages/pymonetdb/mapi.py", line 323, in _getblock_inet
    flag = self._getbytes(2)
  File "/home/kutsurak/.cache/pypoetry/virtualenvs/test-pymonetdb-_ivNU08G-py3.8/lib/python3.8/site-packages/pymonetdb/mapi.py", line 347, in _getbytes
    raise OperationalError("Server closed connection")
pymonetdb.exceptions.OperationalError: Server closed connection

Would it be possible to separate SQL errors from other errors, in particular, connection errors? In that way, it would be much easier for the users to capture and deal with the query exeuction errors differently than all other types of errors.

[gijzelaerr]

yes, thats possible. What Exception do you think would match this case?

[yzchang]

Great. I don't know if there are other types of errors next to SQL errors and connection errors. But for this particular example, when something went wrong with the connection during a query execution, it would be handy to have something like a ConnectionError. Does Python have something standard defined for this?

[gijzelaerr]

https://docs.python.org/3/library/exceptions.html#ConnectionError

[yzchang]

Yes, that'll work. Not sure if you want to give even more detail. Does a BrokenPipeError or a ConnectionResetError apply here? But a ConnectionError is good enough for me.

[gijzelaerr]

Fixed in master and 1.4.0