https://bugs.openldap.org/show_bug.cgi?id=10194

Issue ID: 10194 Summary: Does LMDB support zero length keys? Product: LMDB Version: 0.9.29 Hardware: All OS: All Status: UNCONFIRMED Keywords: needs_review Severity: normal Priority: --- Component: liblmdb Assignee: bugs@openldap.org Reporter: roger.marsh@btinternet.com Target Milestone: ---

I suspect the answer is 'No' but do not see a definitive statement.

I followed the Python code and documentation trail below, but decided to ask here when I concluded I could not decide.

Some Python code was adapted from berkeleydb to lmdb and gave an exception for a cursor.set_range_dup(b'', <some value>) call. Reading the lmdb/cffi.py code in site-packages prompted me to try cursor.set_range(b''), which seemed reasonable given that is what is done for berkeleydb, and it worked.

However cursor.put(b'', <some value>) gave an exception quoting "mdb_put: MDB_BAD_VALSIZE ...".

The documentation for the Python interface to LMDB at lmdb.readthedocs.io/ states behaviour for the empty bytestring for set_key(), set_key_dup(), and set_range(); but not for set_range_dup() or put(). Only set_key() and set_key_dup() describe empty bytestring as an error.