Re: Oracle 11g Virtual Columns?
Date: Mon, 19 Jan 2009 15:51:51 -0600
Message-ID: <%B6dl.9108$hc1.2090_at_flpi150.ffdc.sbc.com>
Robert Klemme wrote:
> On 19.01.2009 09:40, Mladen Gogala wrote:
>> On Sun, 18 Jan 2009 15:34:34 -0800, hpuxrac wrote: >> >>> I guess one way is to have a virtual column and be able to build an >>> index on it. >> >> It was called a "functional index" back in the 8i version.
>
> With the added benefit that you can get the value without using the
> expression which can make your life a lot simpler depending on the
> expression. Basically you get an alias for the expression which makes
> treating columns more uniform than before. Also, this opens some
> migration paths (e.g. you have a column that is rendered redundant by a
> design change, then you can simply replace it by a virtual column saving
> the space).
>
> Btw, MS SQL Server has this quite a long time already. It's called
> "computed column" over there. SCNR :-)
It was also called Computed By in DEC-now-Oracle/Rdb as far back as V3 or V4 (cira 1990-1993?) So the concept is not new - just finally made it into RDBMS.
Way back when Oracle bought Rdb from DEC (December 1994), they originally stated that there would be a merger of the two engines. A lot of what you see in 8/9/10/11 are major functionality in Rdb slowly making its way into RDBMS... examples: the method RMAN uses for doing backups, partitioning, CBO, LMT, Bit-mapped indexes, Computed-by Columns to name just a few... One of the biggest is going to be "versions" or what ever they chose to call it..) which will allow for a RAC database to be upgraded one node at a time. It appears that you can upgrade the db from 11r1 to 11r2 on node1 while still running 11r1 on the other nodes, then bring node1 back online, bounce db on node2 - it is now running 11r2 and so on... Another fine Rdb feature for actually being able to accomplish full rolling upgrades. (its about freakin time...)
When AVAILABILITY counts - THIS is why you want RAC. (and if done correctly, you will also achieve the performance you want. BTW where can I find one of those 120K jobs... I always get "that's the going rate, but not this job" (to which I say - no thanks!) Also most recruiters wouldn't know a qualified candidate if we smacked them up side the head...
>
> Kind regards
>
> robert
>
>
Received on Mon Jan 19 2009 - 15:51:51 CST