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From Rick Hillegas <Richard.Hille...@Sun.COM>
Subject Re: SYSIBM schema
Date Fri, 24 Apr 2009 16:52:36 GMT
Tiago Espinha wrote:
> Rick,
>
> To my understanding, this is like a convenience table. It has exactly 
> one row, which means that when you do "SELECT current date FROM 
> sysibm.sysdummy1" you will get exactly one record with the date.
>
> I am not familiar with the concept of 'vacuous VTI' as you mentioned 
> and if the same can be achieved with that, then my bad.
Hi Tiago,

A VTI (or virtual table) is a function which returns a tabular data set. 
There are a number of these in the SYSCS_DIAG schema. In this case, we 
could write a function which returns an empty data set. This would 
create no locks and so would let us also remove the isolation directives 
which decorate the metadata queries that mention DUMMY1.

Thanks,
-Rick
>
> Tiago
>
> On Fri, Apr 24, 2009 at 5:21 PM, Rick Hillegas 
> <Richard.Hillegas@sun.com <mailto:Richard.Hillegas@sun.com>> wrote:
> >
> > Kathey Marsden wrote:
> >>
> >> Rick Hillegas wrote:
> >>>>
> >>> Thanks Kathey. In the metadata queries it seems to be used to 
> construct empty results sets of specific shapes. That is, its contents 
> are not examined. Those usages could be replaced with a vacuous vti.
> >>>
> >> While we could make this change, we do need to maintain 
> compatibility with older clients so the table would have to remain I 
> think.
> >> Thanks
> >>
> >> Kathey
> >>
> >>
> > Thanks, Kathey. Other than compatibility with old clients, do you 
> see any reason that this table could not be removed eventually?
> >
> > Thanks,
> > -Rick
>


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