Re: using reiserfs as a DB

["Yura Umanets" <umanets@priocom.com>]

Phil Howard wrote:

> "By the keys" means what?  Are the keys the filenames/paths, 

The key in reiserfs seems like four-dimentional coordinate of the 
certain item in filesystem.

The first component is identifier of directory where given object (file 
or directory) lies. Second - identifier of the given object. Third 
component - offset inside object. If object is file, then offset is 
offset inside this file, if directory - hashed name of first entry in 
this direntry. And finally last component is type of the item (statdata, 
direntry, direct item, indirect item).

Therefore it is very fast to access corresponding object item. This is 
just $tree_height blocks to be read.

> Does the raw interface simply shortcut access to files in a normal reiserfs
> mounted filesystem, which can also still be accessed the usual way, or is it
> a special object which can only be accessed that way (if so, then it loses
> the advantage of being able to use conventional tools that work on files, and
> ends up being pretty much a DB lib implemented in kernel space).  Since most
> operations would be open() file, read() file once (because nothing would be
> larger than one block), and close(), a single system call that allowed to
> just fetch the contents given a name would certainly be a plus for the server
> component.


The instance of what is a raw access to files and directories you can 
see on http://reiserfs.linux.kiev.ua/progsreiserfs-0.3.0.tar.gz in 
files: object.c, file.c, dir.c