[openbeos] Re: queries on missing attributes
- From: "Jonas Sundström" <jonas@xxxxxxxxxxx>
- To: openbeos@xxxxxxxxxxxxx
- Date: Tue, 21 Dec 2004 12:42:09 +0100 CET
"Alexander G. M. Smith" <agmsmith@xxxxxxxxxx> wrote:
> Jonas Sundström wrote on Mon, 20 Dec 2004 14:23:50 +0100 CET:
> > Is there a way to make queries on missing attributes?
>
> Since it needs an index to iterate over, you can use the file type to
> just
> check the files you need, or even "name=*" to iterate over all files.
> The
> query would be something like name=*&&attribute="", but that only
> works for
> strings I think. Or maybe you could try name=*&&attribute!=*
I was using (name=*)&&(something else) in my testing. IIRC it would
only return files that had the attribute. I could be wrong though.
Perhaps there's some boolean logic I haven't tested.
> I added a couple of operators in my RAM file system for testing
> attribute
> existance, <>attribute for files including that attribute, and ><
> attribute
> for ones that don't have it (think of the > and < together making an
> X shape
> to cross out the possibility of existance). But since the query
> language
> is implemented by each file system (some wasted effort there - the OS
> should
> just provide indices, let library code do queries), those operators
> are only
> in AGMSRAMFileSystem.
Could this happen in R1 or is it a clear R2 thing?
/Jonas Sundström. www.kirilla.com
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