[postgis-users] how to define an alias for && operator?

[strk at refractions.net]

I would be surprised if you get that function to use an index.
Did you verify it ?
--strk;

On Fri, Nov 04, 2005 at 11:03:05AM -0500, Jean-Pierre Quirion wrote:
> 
> --- Mark Cave-Ayland <m.cave-ayland at webbased.co.uk> a écrit :
> 
> > 
> > > -----Original Message-----
> > > From: postgis-users-bounces at postgis.refractions.net 
> > > [mailto:postgis-users-bounces at postgis.refractions.net] On 
> > > Behalf Of Jean-Pierre Quirion
> > > Sent: 04 November 2005 15:14
> > > To: PostGIS Users Discussion
> > > Subject: RE: [postgis-users] how to define an alias for && operator?
> > 
> > (cut)
> > 
> > > The "OPERATOR 3  <<< RECHECK," line has been added. And this 
> > > does not work. Apparently you can not reuse a 
> > > strategy_number, is this right (3 in this case). [My 
> > > assumptions are based on 
> > > http://www.postgresql.org/docs/8.0/interactive/sql-createopclass.html]
> > > Our problem is not the operator (it works), but the 
> > > association with an index aka operator class. If we used a 
> > > new strategy number like 13, we would have to define a new 
> > > strategy in "lwgeom_gist.c" . I am looking for an easier solution.
> > > 
> > > Jean-Pierre
> > 
> > 
> > Hi Jean-Pierre,
> > 
> > The operator classes are defined in terms of strategy number so you will be
> > unable to do this. The actual modifications in lwgeom_gist.c shouldn't be
> > that bad though - you could probably get away with just defining a new
> > strategy around line 78, e.g.
> > 
> > #define RTNewOverlapStrategyNumber		13
> > 
> > And then simply replace the two occurences of "case
> > RTOverlapStrategyNumber:" with
> > 
> > case RTOverlapStrategyNumber:
> > case RTNewOverlapStrategyNumber:
> > 
> > You should then be able to add your operator by including the following line
> > in your operator class:
> > 
> > "OPERATOR 13  <<< RECHECK"
> > 
> > Kind regards,
> > 
> > Mark.
> 
> Mark,
> Thanks for the hint. If we modified lwgeom_gist.c or any other file, updates of PostGis would be
> less straight forward.
> 
> We found - some minutes ago- the following solution for our original problem (avoiding && in a
> query).
> You probably know that geometry_overlap() does not use the indexes but "&&" does. So we just
> define a new function called "ampamp":
> 
> CREATE function ampamp(geometry,geometry) returns boolean as 'select $1 && $2' language sql;
> 
> The function ampamp() is as serviceable as geometry_overlap() but uses the same indexes as "&&"
> does. 
> 
> Do you see any inconveniences? What is the reason that postgis does not include indexed versions
> of the functions? Maybe nobodies uses the function instead of the operators.
> 
> Kind Regards
> Jean-Pierre
> 
> 
> 
> 
> 
> 
> 	
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