openldap-bugs June 2026

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[Issue 10518] New: Every write transaction leaks a mutex on Windows
by openldap-its＠openldap.org 30 Jun '26

30 Jun '26

https://bugs.openldap.org/show_bug.cgi?id=10518 Issue ID: 10518 Summary: Every write transaction leaks a mutex on Windows Product: LMDB Version: unspecified Hardware: x86_64 OS: Windows Status: UNCONFIRMED Keywords: needs_review Severity: normal Priority: --- Component: liblmdb Assignee: bugs(a)openldap.org Reporter: bhargavabhat(a)gmail.com Target Milestone: --- Created attachment 1152 --> https://bugs.openldap.org/attachment.cgi?id=1152&action=edit Create and use the mutex for the duration of the env I see that on master3 branch, every write transaction leaks a mutex. LMDB creates a new mutex on every non-read-only transaction in `mdb_txn_renew0`. In `mdb_txn_end`, when the write transaction finishes, it sets `mode` to 0 and unlocks it. ``` if (!txn->mt_parent) { env->me_txn = NULL; mode = 0; if (env->me_txns) UNLOCK_MUTEX(env->me_wmutex); } ``` Later, it does this. ``` if (mode & MDB_END_FREE) { if (!F_ISSET(txn->mt_flags, MDB_TXN_RDONLY)) pthread_mutex_destroy(&txn->mt_child_mutex); // never reached free(txn); } ``` So we just don't close the mutex. It's probably not a big deal on non-Windows platforms, but on Windows, the number of handles owned by the process keeps increasing which limits the total number of write transactions we can do in the lifetime of the process. I didn't really understand why we need to create a mutex on every non-read-only transaction. Can we just tie the lifetime of the mutex to the environment instead of the transaction? I'm attaching a patch which tries to fix it. -- You are receiving this mail because: You are on the CC list for the issue.

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[Issue 10395] New: Support multiple readers on uncommitted changes
by openldap-its＠openldap.org 30 Jun '26

30 Jun '26

https://bugs.openldap.org/show_bug.cgi?id=10395 Issue ID: 10395 Summary: Support multiple readers on uncommitted changes Product: LMDB Version: unspecified Hardware: All OS: All Status: UNCONFIRMED Keywords: needs_review Severity: normal Priority: --- Component: liblmdb Assignee: bugs(a)openldap.org Reporter: renault.cle(a)gmail.com Target Milestone: --- Created attachment 1086 --> https://bugs.openldap.org/attachment.cgi?id=1086&action=edit A patch to support multiple readers on uncommitted changes Hello, The attached patch is not meant to be merged immediately into LMDB. Still, it demonstrates how I added a helpful feature to the key-value store: reading uncommitted changes from multiple transactions. I am conscious that the patch still requires some work and uses non-C99 features, i.e., atomics are C11, which could be a blocker for it to be merged upstream. I would also be delighted to merge these changes under a flag/define to ensure we don't impact other users with non-C99 stuff. The main feature we need at Meilisearch is to read uncommitted changes from multiple threads, compute parallel post-processing of different data structures [1], and speed up the search requests. We could have done the post-processing in a following transaction by opening multiple read transactions, but this would mean that the post-processed data structure would not include newly inserted or modified document IDs. Both data structures would be desync. Regarding the design choice, I decided to follow the same design as the nested write transactions: use the parent argument of the mdb_txn_begin [2], and allow the MDB_RDONLY flag, which was disallowed when the parent argument was non-NULL [3]. I find it clear enough that, by calling the mdb_txn_begin function with these arguments, you can call it multiple times (I need to update the doc) to obtain nested read-only transactions from the parent write transaction. ret = mdb_txn_begin(env, parent_txn, MDB_RDONLY, new_nested_rtxn); Note that this early proposal lacks security and error handling. The generated transactions are fake-read-only and actually write transactions that share the underlying parent allocations and data structures. This is unsafe and must be changed or reviewed carefully, but most importantly, we need to add read-only capabilities to these transactions to disallow writes. Using a Rust wrapper on top of LMDB, I wrapped the fake read-only transactions into ReadTxn, which disallows any writes at compile time. However, I haven't checked the conflict database creations or openings. The main issues I encountered were concurrent free of the main shared data structures when the different threads owning the transactions were dropping the transactions simultaneously. So, I decided to implement the equivalent of an ARC to free resources only when the last nested transaction was freed. I can share numbers about how this feature improves the post-processing by 4x-9x or from 1200s to 120s [1]. You can look at this PR, which I would be happy to merge once an improved version of this patch lands on LMDB upstream. I would be very happy if you could guide me a bit on how I could improve this patch to make it mergeable into LMDB. We want to contribute useful features like this to LMDB and not keep a deviant fork. LMDB works great; we are happy about it, and its performance is predictable. Have a lovely week, kero [1]: https://github.com/meilisearch/meilisearch/pull/5307 [2]: https://github.com/LMDB/lmdb/blob/14d6629bc8a9fe40d8a6bee1bf71c45afe7576b6/… [3]: https://github.com/LMDB/lmdb/blob/14d6629bc8a9fe40d8a6bee1bf71c45afe7576b6/… -- You are receiving this mail because: You are on the CC list for the issue.

1 32

[Issue 9619] New: mdb_env_copy2 with MDB_CP_COMPACT in mdb.master3 produces corrupt mdb file
by openldap-its＠openldap.org 30 Jun '26

30 Jun '26

https://bugs.openldap.org/show_bug.cgi?id=9619 Issue ID: 9619 Summary: mdb_env_copy2 with MDB_CP_COMPACT in mdb.master3 produces corrupt mdb file Product: LMDB Version: 0.9.29 Hardware: All OS: Windows Status: UNCONFIRMED Severity: normal Priority: --- Component: liblmdb Assignee: bugs(a)openldap.org Reporter: kriszyp(a)gmail.com Target Milestone: --- When copying an LMDB database with mdb_env_copy2 with the MDB_CP_COMPACT with mdb.master3, the resulting mdb file seems to be corrupt and when using it in LMDB, I get segmentation faults. Copying without the compacting flag seems to work fine. I apologize, I know this is not a very good issue report, as I haven't had a chance to actually narrow this down to a more reproducible/isolated case, or look for how to patch. I thought I would report in case there are any ideas on what could cause this. The segmentation faults always seem to be memory write faults (as opposed to try fault on trying to read). Or perhaps the current backup/copying functionality is eventually going to be replaced by incremental backup/copying anyway (https://twitter.com/hyc_symas/status/1315651814096875520). I'll try to update this if I get a chance to investigate more, but otherwise feel free to ignore/consider low-priority since the work around is easy. -- You are receiving this mail because: You are on the CC list for the issue.

1 14

[Issue 9496] New: Some writes missing from database
by openldap-its＠openldap.org 30 Jun '26

30 Jun '26

https://bugs.openldap.org/show_bug.cgi?id=9496 Issue ID: 9496 Summary: Some writes missing from database Product: LMDB Version: unspecified Hardware: All OS: All Status: UNCONFIRMED Severity: normal Priority: --- Component: liblmdb Assignee: bugs(a)openldap.org Reporter: igfoo(a)github.com Target Milestone: --- With the attached test program, some of my database writes appear not to actually be written to the database. For example, a run may look like this: $ ./run.sh All done. All finished 1802 test.txt foo_200 is missing bar_200 is missing foo_404 is missing bar_404 is missing foo_407 is missing bar_407 is missing The script that I am using to run the program is below. This is using mdb.master 52bc29ee2efccf09c650598635cd42a50b6ecffe on Linux, with an ext4 filesystem. Is this an LMDB bug, or is there a bug in my code? Thanks Ian #!/bin/sh set -e if ! [ -d lmdb ] then rm -rf lmdb git clone https://github.com/LMDB/lmdb.git INSTALL_DIR="`pwd`/inst" cd lmdb/libraries/liblmdb make install prefix="$INSTALL_DIR" cd ../../.. fi gcc -Wall -Werror -Iinst/include loop.c inst/lib/liblmdb.a -o loop -pthread rm -f test.db test.db-lock ./loop echo "All finished" mdb_dump -np test.db > test.txt wc -l test.txt for i in `seq 100 999` do if ! grep -q "foo_$i" test.txt then echo "foo_$i is missing" fi if ! grep -q "bar_$i" test.txt then echo "bar_$i is missing" fi done -- You are receiving this mail because: You are on the CC list for the issue.

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[Issue 10024] New: MDB_PREVSNAPSHOT broken
by openldap-its＠openldap.org 30 Jun '26

30 Jun '26

https://bugs.openldap.org/show_bug.cgi?id=10024 Issue ID: 10024 Summary: MDB_PREVSNAPSHOT broken Product: LMDB Version: unspecified Hardware: All OS: All Status: UNCONFIRMED Keywords: needs_review Severity: normal Priority: --- Component: liblmdb Assignee: bugs(a)openldap.org Reporter: markus(a)objectbox.io Target Milestone: --- It seems that the patch #9496 had a negative side effect on MDB_PREVSNAPSHOT. In certain cases, when opening the DB using MDB_PREVSNAPSHOT, the previous (2nd latest) commit is not selected. Instead, reads show that the latest commit was selected voiding the effect of MDB_PREVSNAPSHOT. I observed this in our test cases a while back. Today, I was finally able to reproduce it and debug into it. When creating the transaction to read the data, I debugged into mdb_txn_renew0. Here, ti (MDB_txninfo; env->me_txns) was non-NULL. However, ti->mti_txnid was 0 (!) and thus txn->mt_txnid was set to 0. That's the reason for always selecting the first (index 0) meta page inside mdb_txn_renew0: meta = env->me_metas[txn->mt_txnid & 1]; This line occurs twice (once for read txn and once for write txn; it affects both txn types). Thus, the chances of MDB_PREVSNAPSHOT selecting the correct meta page is 50-50. It's only correct if the first meta page (index 0) is the older one. I believe that this is related to #9496 because the patch, that was provided there, removed the initialization of "env->me_txns->mti_txnid" in mdb_env_open2. This would explain why txn->mt_txnid inside mdb_txn_renew0 was set to 0. I can confirm that adding back the following two lines back in fixes MDB_PREVSNAPSHOT: if (env->me_txns) env->me_txns->mti_txnid = meta.mm_txnid; The said patch including the removal of these two lines was applied in the commit(s) "ITS#9496 fix mdb_env_open bug from #8704" (Howard Chu on 09.04.21). I hope this information is useful to find a suitable fix. Please let me know if you have questions. Also, I'd be happy to help confirming a potential fix with our test suite. -- You are receiving this mail because: You are on the CC list for the issue.

1 8

[Issue 10521] New: read-only transaction under a read-only transaction
by openldap-its＠openldap.org 30 Jun '26

30 Jun '26

https://bugs.openldap.org/show_bug.cgi?id=10521 Issue ID: 10521 Summary: read-only transaction under a read-only transaction Product: LMDB Version: unspecified Hardware: All OS: All Status: UNCONFIRMED Keywords: needs_review Severity: normal Priority: --- Component: liblmdb Assignee: bugs(a)openldap.org Reporter: bhargavabhat(a)gmail.com Target Milestone: --- Since the fix to #10395 was merged, I see that we can create a read-only transaction as a child of another read-only transaction. But the comment in mdb_txn_begin() says /* Nested transactions: * Only write txns may have nested txns; * if the nested txn is a write txn there may only be 1, no writemap; * if the nested txn is a read txn there may be arbitrarily many. */ I interpret the first statement above as "read-only transaction can't be a parent of another transaction". Is my interpretation correct? -- You are receiving this mail because: You are on the CC list for the issue.

1 5

[Issue 9011] add mdb_txn_flags()
by openldap-its＠openldap.org 30 Jun '26

30 Jun '26

https://bugs.openldap.org/show_bug.cgi?id=9011 Quanah Gibson-Mount <quanah(a)openldap.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|RESOLVED |VERIFIED -- You are receiving this mail because: You are on the CC list for the issue.

1 0

[Issue 8978] Fix mdb_env_open2() failing when getting handle for NTDLL.dll
by openldap-its＠openldap.org 30 Jun '26

30 Jun '26

https://bugs.openldap.org/show_bug.cgi?id=8978 Quanah Gibson-Mount <quanah(a)openldap.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|RESOLVED |VERIFIED -- You are receiving this mail because: You are on the CC list for the issue.

1 0

[Issue 7794] RFE: Versioned LMDB shared library
by openldap-its＠openldap.org 30 Jun '26

30 Jun '26

https://bugs.openldap.org/show_bug.cgi?id=7794 Quanah Gibson-Mount <quanah(a)openldap.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|RESOLVED |VERIFIED -- You are receiving this mail because: You are on the CC list for the issue.

1 0

[Issue 8579] LMDB: me_fd should be O_CLOEXEC on POSIX systems
by openldap-its＠openldap.org 30 Jun '26

30 Jun '26

https://bugs.openldap.org/show_bug.cgi?id=8579 Quanah Gibson-Mount <quanah(a)openldap.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|RESOLVED |VERIFIED -- You are receiving this mail because: You are on the CC list for the issue.

1 0

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openldap-bugs June 2026