On Fri, 2014-03-28 at 04:58 +0000, armon.dadgar@gmail.com wrote:

I have a gist demonstrating this: https://gist.github.com/armon/9825666

Some notes about this code: // LMDB will return EINVAL(22) for the GET_CURRENT op if // there is no further keys. We treat this as no more // keys being found. if num, ok := err.(mdb.Errno); ok && num == 22 { println("errno 22") err = mdb.NotFound }

The value of EINVAL is OS-dependent, it need not be 22.

EINVAL means you did something wrong, it's a bad idea to assume it means any particular wrong thing. For one thing, mdb might not keep catching that error. I'd follow up with a test check that there are indeed no more keys.

That said, mdb_cursor_del() followed by MDB_GET_CURRENT seems to me a sensible thing to want to do. So I think MDB_GET_CURRENT should return MDB_NOTFOUND here. And maybe also after cursor_next() returned MDB_NOTFOUND, and on an empty DB. OTOH maybe cursors would need to keep more state to tell this from user errors which should get EINVAL.