Re: btree on disk

On 7/10/07, Cam Bazz <[email protected]> wrote:
> Hello Natalia;
>
> If I were to put records inside a BTreeFiler in a way:
>
>
> filer.writeRecord(new Key(somekeyvalue),new Value(somevalue))
>
> and then search this filer based on somekeyvalue, would I have to use a
> ValueIndexer?

No, you do not need indexer for that. Searching by a key is the
fastest way to find a record. ValueIndexer is used when you store XML
and want to search data based on element/attribute values.

> A typical operation is for adding nodes to a graph is:
>
> record r;
> if(filer.readRecord(new Key(keysearched))==null)
> {
>    r = new Record(new Key(keysearched), new Value(somevalue));
>    filer.writeRecord (r);
> }
> else
> {
>   r = filer.readRecord(new Key(keysearched));
> }
>
> it otherwords, I have to check if a graph contains a node n, if it does not
> write a new node, and if it does retrieve the node. I need to be able to do
> this very fast. I have tried object oriented dbms, although they worked
> nicely for graph things, they were very poor at identity search.

That would work. I would suggest to change it a bit, however, so the
code does not read a record twice if key is found - retrieving data
from file system is pretty expensive.

> Any ideas, recomendations and help greatly appreciated,
> -C.B.

Natalia

>
>
> On 7/9/07, Natalia Shilenkova <[email protected] > wrote:
> > On 7/9/07, Cam Bazz <[email protected] > wrote:
> > > Hello All,
> > >
> > > That was really helpful. Thanks.
> > >
> > > I also noticed FSFiler, and HashFiler. Are those for Indexing files?
> >
> > Xindice allows several way for the data to be stored. Currently it has
> > BTreeFiler (based on tree-like structure), HashFiler (based on hash
> > table), FSFiler (uses file system), MemFiler (in-memory), and
> > SizableMemFiler (in-memory). A document collection can be configured
> > to use any of those filers, depending on collection characteristics.
> >
> > Additionally, collection can have an index. There are 3 indexers in
> > Xindice now: NameIndexer, ValueIndexer, and MemValueIndexer.
> >
> > > I am working on a graph database project. I have tried several oodbms,
> and
> > > finally decided to build my own.
> > >
> > > Also, could it be possible to use xindice as a backend for Jena?
> >
> > No idea, really. Never heard of Jena before.
> >
> > Regards,
> > Natalia
> >
>
>