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RE: Growing an LMDB database after MDB_MAP_FULL

Hi Howard,

Hmm well... how embarrassing.  To me it seemed probable that LMDB has been designed with these rationales in mind: one must have a clear idea of the maximum order of magnitude of the volume to be held by the database, the database must have ACID properties, and (less probably) a single machine will not host a lot of LMDB databases. Given that it seemed probable that when the database is full, you probably had no choice but to fail a transaction (in order to be consistent). But ok, that was a stupid guess and a misunderstanding of LMDB rationales. I'm sorry; I didn't mean to offend anyone.

Anyway, thanks a lot for ITS#8324! I'll give it a try!

Best regards,


-----Message d'origine-----
De : openldap-technical [mailto:openldap-technical-bounces@openldap.org] De la part de Howard Chu
Envoyé : lundi 30 novembre 2015 20:15
À : Bruno Freudensprung <bruno.freudensprung@temis.com>; openldap-technical@openldap.org
Objet : Re: Growing an LMDB database after MDB_MAP_FULL

Bruno Freudensprung wrote:
> Hi,
> I have a question regarding growing an LMDB database when a write 
> transaction hits MDB_MAP_FULL.
> I would like to avoid defining a high mapsize value because my 
> application will contain many MDB_envs, and because I have Windows 
> users

My condolences.

> (Windows allocates the whole file on the disk).

See ITS#8324.

> Based on the intuition that MDB_MAP_FULL should not leave the database 
> in a weird state, I have made the following little experiment. When 
> MDB_MAP_FULL is encountered I tried to:

> ·copy the current env (mdb_env_copy) into another directory (fine: it 
> does not seem to contain uncommited data)
> ·reset the transaction « error  bit » (modified LMDB code to introduce 
> a «
> txn->mt_flags &= ~MDB_TXN_ERROR » somewhere)

You're being stupid. You think we add error flags just for the fun of it? When you get an error like this you must abort the current transaction. Does the documentation not state this clearly enough?

   -- Howard Chu
   CTO, Symas Corp.           http://www.symas.com
   Director, Highland Sun     http://highlandsun.com/hyc/
   Chief Architect, OpenLDAP  http://www.openldap.org/project/