Re: B*-trees

Christoph Rupp wrote:
> 1. It's a good idea to separate the B-tree with the indices and the data
> of the table entries in different files, isn't it? It should give you
> the possibility to put both files on different hard drives and therefore
> speed up things... and it's easier to reorganize the b-tree without
> touching the data file.

Hi Christoph,

typically the database file uses pages of some sort, to store different objects (tables, indices, whatever) to different places.

A friend of mine also has an approach for balancing the load between drives or computers.
He even zips data before seding it to it's destination. You might send him a mail:
mailto:adrian_at_veith-system.de
Don't worry about the homepage and don't add an "s" to "system".

> 2. Are there any advantages when i save the different B-Trees to
> different files, too (i.e. one b-tree per file?)

In practice using different files is very inconvenient for backup, copying and redistribution reasons.
Users often come into trouble by mixing files. Not everyone works in a clean-room lab, where files are uncorrupted, disks are free and only experts touch the server.

Cacheing could also be an argument against many files.

Depending on the structure of your data, reading from one file could also be faster, if one read operation gets more than one index table.

Most of the time "Build the simplest thing that could possibly work." is quite good on performance.
If you have different files, managing files is overhead.

> 3. Is there a kind of "Tiny-SQL"-standard which offers a very reduced
> instruction set or do i have to define my own query language?

I don't know what kind of database you want to implement.

If you think about creating an object database, query-by-example might be convenient.
Have a look at our interface to get an idea: http://www.db4o.com/db4o/doc1/index.html

We hope to work on a more sophisticated interface in the near future: http://www.egroups.com/group/oodb

Kind regards,
Carl

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Carl Rosenberger
db4o - database for objects - http://www.db4o.com