[openbeos] Re: queries on missing attributes

> "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 recall some ppl saying =="*" and =="**" produced different outputs, 
you might want to try both. (why I don't know, well "*X" means ends 
with X, "X*" means starts with X, maybe "*" only means ends with 
nothing to some fs, while "**" means contains '', which is semantically 
different ?)

> > 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.

Btw, your code is a bit... hairy I'd say :P
Will have to write my own parser for googlefs :-(
Would really be useful to have that available as a module.
/me adds a TODO item nr 46763276.

François.

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