Re: (ITS#8264) LMDB mdb_del in a cursor causes data loss in certain situations
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malyn(a)strangeGizmo.com wrote:
Full_Name: Michael Alyn Miller
Version: LMDB 0.9.14, Git head
OS: Windows 8.1 x64, NixOS 14.12 x64
URL: ftp://ftp.openldap.org/incoming/michael-alyn-miller-151005.c
Submission from: (NULL) (96.251.78.237)
I have a helper library that sits on top of LMDB and testing some of the
abstractions in that library has exposed a bug in LMDB related to deleting items
while inside of a cursor. I have reduced the repro down to a test case that
operates directly against LMDB.
The test in question adds three groups of keys to the database (each with a
different prefix) and then deletes the third group of keys. The deletion is
done by scanning all of the keys with that prefix using a cursor.
mdb_cursor_del works correctly and deletes only the targeted keys, whereas
mdb_del causes nine extra keys (not in that group/prefix) to be deleted.
I have tested this code against LMDB 0.9.14 and Git head 8b46dcc.
Please let me
know if you need any additional information. Thank you for your time!
Unable to reproduce.
violino:~/OD/mdb/libraries/liblmdb> gcc -g -c michael-alyn-miller-151005.c
violino:~/OD/mdb/libraries/liblmdb> gcc -o mic michael-alyn-miller-151005.o
-pthread liblmdb.a
violino:~/OD/mdb/libraries/liblmdb> ./mic
Num items after deletion using mdb_cursor_del: 44 (correct)
Num items after deletion using mdb_del: 44 (correct)
violino:~/OD/mdb/libraries/liblmdb> git log
commit 8b46dcc26d1e9897ab1da3a4a164cad4a4479a52
Author: Howard Chu <hyc(a)openldap.org>
Date: Sun Oct 4 01:56:25 2015 +0100
ITS#8258 fix rebalance/split
The tree height can also increase during rebalance, not just shrink.
This can happen if update_key needs to split a parent branch page.
--
-- Howard Chu
CTO, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc/
Chief Architect, OpenLDAP http://www.openldap.org/project/
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