[LMDB] some few questions

[Klaus Malorny <Klaus.Malorny@knipp.de>]

Hi,

LMDB seems to be quite the right database I am looking for in order to speed up 
my application. However, I still need to figure some things out. While I could 
get many answers to my questions by skimming through the archive, the following 
things are still unclear to me, and it would be quite nice if someone could 
clarify them:

- in the documentation, I saw two limits: the key is limited to 511 bytes
  (by default) and the data is limited to 16777215 bytes. Is this correct?
  For larger data sizes, is the data still maintained in one contiguous
  block, so that the application can still access it directly without any
  need of copying within LMDB? Or it is better to split larger data into
  multiple key/value pairs?

- I discovered the return code "MDB_TXN_FULL". By what means are transactions
  limited? I might consider to use few, but quite large transactions dealing
  with hundreds of thousands key/value pairs to be created, updated or deleted
  in some circumstances.

- I saw the discussion about the predefined database size, and that it is
  recommended to use a never-to-be-reached size and to rely on the sparse file
  capabilities of the underlying OS. If I would not want to go this way:
  Is it correct that if I encounter an "MDB_MAP_FULL" return code, it
  would be sufficient to abort the current transaction, resize the database
  using mdp_env_set_mapsize and repeat the transaction?

Thanks in advance and regards,

Klaus