RE: back-bdb future

["Howard Chu" <hyc@highlandsun.com>]

> -----Original Message-----
> From: Jonghyuk Choi [mailto:jongchoi@us.ibm.com]

> >At one point Kurt mentioned exploring using BDB itself for the cache,
> using a
> >memory-only database. Has anyone looked into this? I wonder what the
> >semantics are for such a database in a transaction
> environment, since it
> has
> >no persistent store.
>
> BDB cache's gain over database page cache may not be large.
> In addition to the normal DB access overhead, transaction
> subsystem adds
> 3~7% of excess overhead even for non-transaction protected searches.
> so... entry cache would still be considered as a higher perf store.
> - Jong

My wording may not have been too clear. I am not talking about using a
memory-only BDB database to store entries in a disk-datbase-style format. I
mean using the memory-only database to store the pointers to the cached
entries, instead of using libavl. The question is whether a hashing scheme,
or a Btree scheme, might be more efficient than an AVL tree.

However, your point about DB overhead probably still stands.

  -- Howard Chu
  Chief Architect, Symas Corp.       Director, Highland Sun
  http://www.symas.com               http://highlandsun.com/hyc
  Symas: Premier OpenSource Development and Support