Unfortunately PQcancel blocks, so it's not better than PQgetResult.
It has been suggested to use PQreset in non-blocking way but this would give
the Python program the burden of handling a connection done but not configured
in an unexpected place.
If the network is down, trying to read blocking will hang the process hard
(ctrl-c not working). Send a cancel signal instead (as suggested in
http://archives.postgresql.org/pgsql-hackers/2012-07/msg00903.php) and go
back into a green polling: this should allow a further error (e.g. another
ctrl-c) to break the loop. In this case we cannot assume anything about
the state of the connection, so we close it.
Unfortunately PQcancel blocks, so it's not better than PQgetResult.
It has been suggested to use PQreset in non-blocking way but this would give
the Python program the burden of handling a connection done but not configured
in an unexpected place.
If the network is down, trying to read blocking will hang the process hard
(ctrl-c not working). Send a cancel signal instead (as suggested in
http://archives.postgresql.org/pgsql-hackers/2012-07/msg00903.php) and go
back into a green polling: this should allow a further error (e.g. another
ctrl-c) to break the loop. In this case we cannot assume anything about
the state of the connection, so we close it.
TypeError is the standard Python error raised in this case:
$ python -c "(lambda a: None)(b=10)"
TypeError: <lambda>() got an unexpected keyword argument 'b'
We only used to raise InterfaceError when connect was used without
any parameter at all, so it's hard to think a program depending on
that design. Furthermore the function has always raised (and still
does) OperationalError too, if the bad argument is detected by the
libpq, and that cannot be changed because we can't tell the
difference from a normal connection error.
TypeError is the standard Python error raised in this case:
$ python -c "(lambda a: None)(b=10)"
TypeError: <lambda>() got an unexpected keyword argument 'b'
We only used to raise InterfaceError when connect was used without
any parameter at all, so it's hard to think a program depending on
that design. Furthermore the function has always raised (and still
does) OperationalError too, if the bad argument is detected by the
libpq, and that cannot be changed because we can't tell the
difference from a normal connection error.
