Full_Name: Dimitrij Denissenko Version: OS: Ubuntu 12.04 URL: Submission from: (NULL) (62.30.100.0)

Hi,

I found an interesting issue with LMDB. I have populated the DB with a bunch of records and it uses ~30M on disk (after sync). Then I added a background process to my app and populated the database again with the same record set. Surprisingly. the resulting size on disk was >70M.

The background process is forked periodically to perform some maintenance tasks, here is my (simplified) code:

/* Close env before forking */ mdb_env_close(env);

if ((childpid = fork()) == 0) { /* Child */ rc = mdb_env_open(env, ".", MDB_NOSYNC, 0644); ... } else { /* Parent */ rc = mdb_env_open(env, ".", MDB_NOSYNC, 0644); ... }

I could narrow it down to the mdb_env_open call in the child. If I add exit(0) before the mdb_env_open line, the DB size remains consistently at ~30M. The data size seems to grow proportionally to the number of forks performed during data load. What could be causing the growth? What can I do to prevent it?

Thanks in advance

PS: I tried it with MDB_FIXMAP and without, same result.