Re: Help Data-Types

>>My betting is that a CPU can do bit shifts quicker that getting a 11
more
>>bytes from RAM/disk

> Seems reasonable - but is it really so?

Of course it all depends where that data is. The outer edge of a disk when the head is at the inner? Well a 32 way SMP clocked at say 2GHz with 4 execution units in each CPU could theoretically notchup say 4 * 2*10^9 * 32 / .2 instructions in the 200 milliseconds it takes to retrieve that extra data. Even getting stuff from Level2, 3 & 4 RAM takes time. Plus you only need to do the bit shifts/arithmetic/string ops when displaying results to users. Joins, sorts etc can use the 'internal format'.
On the other hand with a M/F with lots of I/O and not so much CPU, biasing internal representations away from those with compute heavy requirements can be a sensiable idea (e.g. store DATE TIMEs in BCD not num secs since 1971).

> I am asking since you did do a project with that representation and I
> guess that you did some testing

Nope, it's just common sense (or not so common apparently...) Think of it this way. Which is quicker, creating a summary table from 2 TBs of data or 4TBs? Answers on a postcard please.

>>With a DBMS that supports multiple possible representations (of
DataTypes)
>>one does not need to choose between different representation at the
>>logical level.

>I was under impression that by deciding between 4 properties and 1
>property of appropriate domains one chooses more than a physical
>representation.
>I thought that the process of determining weather IP is a scalar value
>property or non-scalar falls under logical modeling regardless of
>representation?

With a DBMS that supports multiple possible expressible databases (i.e. view/table interchangeability as long as they are information equivalent), one does not need to choose a primary representation at the logical level. IP is scalar or it is non-scalar depending on which expressible database a user happens to be looking at.

Rather a nice parallel with multiple possible representations I think.

Anyone out there got a DBMS that supports such things?!?

Regards
Paul Vernon
Business Intelligence, IBM Global Services   Received on Tue Aug 20 2002 - 18:51:09 CEST