From the DB-API (https://www.python.org/dev/peps/pep-0249/):
OperationalError
Exception raised for errors that are related to the database's
operation and not necessarily under the control of the programmer,
e.g. an unexpected disconnect occurs, [...]
Additionally, psycopg2 was inconsistent, at least in the async case:
depending on how the "connection closed" error was reported from the
kernel to libpq, it would sometimes raise OperationalError and
sometimes DatabaseError. Now it always raises OperationalError.
There's a race condition that only seems to happen over Unix-domain
sockets. Sometimes, the closed socket is reported by the kernel to
libpq like this (captured with strace):
sendto(3, "Q\0\0\0\34select pg_backend_pid()\0", 29, MSG_NOSIGNAL, NULL, 0) = 29
recvfrom(3, "E\0\0\0mSFATAL\0C57P01\0Mterminating "..., 16384, 0, NULL, NULL) = 110
recvfrom(3, 0x12d0330, 16384, 0, 0, 0) = -1 ECONNRESET (Connection reset by peer)
That is, psycopg2/libpq sees no error when sending the first query
after the connection is closed, but gets an error reading the result.
In that case, everything worked fine.
But sometimes, the error manifests like this:
sendto(3, "Q\0\0\0\34select pg_backend_pid()\0", 29, MSG_NOSIGNAL, NULL, 0) = -1 EPIPE (Broken pipe)
recvfrom(3, "E\0\0\0mSFATAL\0C57P01\0Mterminating "..., 16384, 0, NULL, NULL) = 110
recvfrom(3, "", 16274, 0, NULL, NULL) = 0
recvfrom(3, "", 16274, 0, NULL, NULL) = 0
i.e. libpq received an error when sending the query. This manifests as
a slightly different exception from a slightly different place. More
importantly, in this case connection.closed is left at 0 rather than
being set to 2, and that is the bug I'm fixing here.
Note that we see almost identical behaviour for sync and async
connections, and the fixes are the same. So I added extremely similar
test cases.
Finally, there is still a bug here: for async connections, we
sometimes raise DatabaseError (incorrect) and sometimes raise
OperationalError (correct). Will fix that next.
This is for people using dtuple.py; a dtuple.DatabaseTuple instance
keeps a reference to cursor.description, which is not picklable because
psycopg2 doesn't export the Column namedtuple it uses.
This commit exports the Column namedtuple, and includes a test to verify
the pickle/unpickle works after exporting Column.
Makes invocation from subclasses and generic code easier.
Code simplified by using default values for keyword arguments
and avoiding needless conversions back and forth between Python and C
strings. Also added connection type check to cursor's init.
Actually *it doesn't*: once we iterate the first itersize records, rowcount
is reset to zero. If we want to fix it we need an extra member in the
cursor.
- Raise an exception on incomplete placeholders.
- Minor speedups.
- Don't change the string in place (??!!) if the placeholder is not s
and the value is null.
The latter point can be done because downstream we don't accept anything
different from s anyway (in the Bytes_Format function).
Notice that now the format string is constant whatever the arguments.
This means that executemany is still more inefficient than it should be
as mogrify may work only on the parameters. However this is an
implementation only worthwhile if we start supporting real parameters.
Let's talk about that for the next release.
The value is used to control the number of records to fetch per network
roundtrip in named cursors iteration. Used to avoid the inefficient
arraysize default of 1 without giving this value the magic meaning of
2000.
Dropped cyclic import from modules to tests: they were only working
because a second copy of the package was found in the project dir.
Use relative import so that 2to3 can do a good conversion.
