Re: Including Snapshot Info with Indexes

On 10/14/07, Trevor Talbot <quension@gmail.com> wrote:

On 10/14/07, Gokulakannan Somasundaram <gokul007@gmail.com> wrote:

> http://www.databasecolumn.com/2007/09/one-size-fits-all.html

> > > The Vertica database(Monet is a open source version with the same
> > > principle) makes use of the very same principle. Use more disk space,
> > > since they are less costly and optimize the data warehousing.

> What i  meant there was, it has duplicated storage of certain columns of the
> table. A table with more than one projection always needs more space, than a
> table with just one projection. By doing this they are reducing the number
> of disk operations. If they are duplicating columns of data to avoid reading
> un-necessary information, we are duplicating the snapshot information to
> avoid going to the table.

Was this about Vertica or MonetDB?  I saw that article a while ago,
and I didn't see anything that suggested Vertica duplicated data, just
that it organized it differently on disk.  What are you seeing as
being duplicated?

Hi Trevor,
             This is a good paper to read about the basics of Column-oriented databases.
http://db.lcs.mit.edu/projects/cstore/vldb.pdf
If you goto the Section 2 - Data Model. He has shown the data model, with a sample EMP table.

The example shows that EMP table contains four columns - Name, Age, Dept, Salary
From this table, projections are being formed - (In the paper, they have shown the creation of four projections for Example 1)
EMP1 (name, age)
EMP2 (dept, age, DEPT.floor)
EMP3 (name, salary)
DEPT1(dname, floor)

As you can see, the same column information gets duplicated in different projections.
The advantage is that if a query is around name and age, it need not skim around other details. But the storage requirements go high, since there is redundancy. As you may know, if you increase data redundancy, it will help selects at the cost of inserts, updates and deletes.

This is what i was trying to say.

Thanks,
Gokul.