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Re: lmdb: is read operation permitted inside the write transaction?
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
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)
Will it be always valid data?
...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.