On Tue, 2015-05-19 at 17:05 +0100, Howard Chu wrote:
Timur Kristóf wrote:
> On Mon, 2015-05-18 at 23:03 +0200, Hallvard Breien Furuseth wrote:
> > On 12/05/15 19:36, Howard Chu wrote:
> > > Dmytro Milinevskyy wrote:
> > > > Basically I need to have an opportunity to call mdb_get while
> > > > in
> > > > write
> > > > transaction.
> > > > The sequence is smth like:
> > > > - txn = mdb_txn_begin(flags=0)
> > > > for i in 0..x:
> > > > - v = mdb_get(txn, i)
> > > > - mdb_put(txn, x+i, v)
> > > > - mdb_put(txn, i, v+1)
> > > > - mdb_txn_commit(txn)
> > > >
> > > > Will it be always valid data?
> > >
> > > Yes.
> > ...No. I expect he means v = the MDB_val returned by mdb_get().
> > mdb_put() can modify the data it points at.
Since he's using "v+1" in his example I assumed he's making a local
the returned values. Anyway, the plain answer to the question in the
> > See the MDB_val documentation in ldmb.h:
> > * Values returned from the database are valid only until a
> > subsequent
> > * update operation, or the end of the transaction. Do not
> > modify or
> > * free them, they commonly point into the database itself.
> What exactly does a subsequent update operation mean? Overwriting
> value of the same key,
If we meant "same key" we would have said so.
Okay, thanks for the clarification!
> or any mdb_put or mdb_cursor_put operation at
> all, regardless of which key they touch?