Re: Materialized Views

On Tue, Dec 23, 2008 at 8:18 PM, Michael Fontana <mfontana@xxxxxxxxxxx>wrote:

>  You need to know more about a feature before you can truly decide it's
> required.
>
>  While it's allowed and there may be some valid reasons for it, often there
> are not.  MVs are most often used to create distributed versions of data.  T
>
Hi Michael

Complex aggregations, or rather complex aggregations that do not perform
sufficiently raidly but which can be pre-calculated, are the other major
reason for this feature in a reporting/dss type environment. To quote from
the DataWarehousing guide

One technique employed in data warehouses to improve performance is the
creation of summaries. Summaries are special types of aggregate views that
improve query execution times by precalculating expensive joins and
aggregation operations prior to execution and storing the results in a table
in the database. For example, you can create a summary table to contain the
sums of sales by region and by product.

So it rather sounded to me that Lee's developers reasons for using MVs
looked to be not unreasonable. Having said all that, I;ve only ever really
dealt with the remote view use for them, and you are absolutely right about
the detection of out of date snapshots in that context.



>
>
>
> --
> Niall Litchfield
> Oracle DBA
> http://www.orawin.info
>

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