19 May
2015
19 May
'15
8:39 a.m.
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.
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 the value of the same key, or any mdb_put or mdb_cursor_put operation at all, regardless of which key they touch?