Re: LMDB: MDB_MAP_FULL doesn't allow deletions

[Howard Chu <hyc@symas.com>]

Jeremy Bernstein wrote:
> Although I didn't figure out a good way to do what I want, this is what I am
> now doing:
>
> if (MDB_MAP_FULL while putting) {
>    abort txn, close the database
>    reopen the database @ larger mapsize
>    perform some pruning of dead records
>    commit txn, close the database
>    reopen the database @ old mapsize
>    try to put again
> }
>
> At this point, the database is probably larger than the old mapsize. To handle
> that, I make a copy  of the DB, kill the original, open a new database and
> copy the records from the old DB to the  new one.
>
> All of this is a lot more complicated and code-verbose than I want, but it
> works and seems to be reliable.
>
> Nevertheless, if there's an easier way, I'm all ears. Thanks for your
> thoughts.

Use mdb_stat() before performing the _put(). If the total number of pages in 
use is large (whatever threshold you choose, e.g. 90%) then start pruning.

Look at the mdb_stat command's output to get an idea of what you're looking for.
--
  -- Howard Chu
  CTO, Symas Corp.           http://www.symas.com
  Director, Highland Sun     http://highlandsun.com/hyc/
  Chief Architect, OpenLDAP  http://www.openldap.org/project/