[fdo-internals] RE: FDO Function SpatialExtents

[Haris Kurtagic]

Traian,

Now I don't understand you :)

 

I would believe SpatialExtents should return exact MBR value of
geometries in Select query.

 

Haris

 

 

From: fdo-internals-bounces at lists.osgeo.org
[mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Traian
Stanev
Sent: Tuesday, November 18, 2008 12:04 AM
To: 'FDO Internals Mail List'
Subject: RE: [fdo-internals] RE: FDO Function SpatialExtents

 

 

Theoretically it has to return the MBR of its argument. 

 

In practice, it doesn't need to be exact, since the code that uses it
does not need it to be exact.

 

You don't have a choice anyway, if you want it to perform at all...

 

Traian

 

 

From: fdo-internals-bounces at lists.osgeo.org
[mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Haris
Kurtagic
Sent: Monday, November 17, 2008 6:22 PM
To: FDO Internals Mail List
Subject: RE: [fdo-internals] RE: FDO Function SpatialExtents

 

Hm, but what is SpatialExtent function, exact MBR or not ?

 

Haris

 

From: fdo-internals-bounces at lists.osgeo.org
[mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Traian
Stanev
Sent: Monday, November 17, 2008 11:54 PM
To: FDO Internals Mail List
Subject: RE: [fdo-internals] RE: FDO Function SpatialExtents

 

 

Yes, just return the bounding box of all the geometries. Map does not
need exact BBOX, just an extent it can zoom to in order to show
something once you add the layer.

 

Traian

 

 

From: fdo-internals-bounces at lists.osgeo.org
[mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Haris
Kurtagic
Sent: Monday, November 17, 2008 6:16 PM
To: FDO Internals Mail List
Subject: RE: [fdo-internals] RE: FDO Function SpatialExtents

 

Yes, SDO_AGGR_MBR could be slow.

In Oracle there is index METADATA table with SDO_ROOT_MBR ( perhaps that
is what Orest was saying ? ) but that is not correct MBR of geometries.

 

I understood that SelectExtents is supposed to :

return exact MBR of geometries

works for SQL queries, works for subsets of data

 

It looks to me that Map is using SpatialExtents it to get not necessary
exact extent of layer (class) not geometries.

 

So my question is, is SpatialExtents supposed to return MBR of
geometries ?

 

I think for class extent we should have another command.

 

Haris

 

 

From: fdo-internals-bounces at lists.osgeo.org
[mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Robert
Fortin
Sent: Monday, November 17, 2008 11:24 PM
To: FDO Internals Mail List
Subject: [fdo-internals] RE: FDO Function SpatialExtents

 

Map will use the SelectExtents function (if is exists) in order to
compute the extent of the data set before it starts populating the
cache.

The slower the SelectExtents  function is the slower Map rendering will
be.  SDO_AGGR_MBR is probably not efficient enough for that purpose.

 

RF

 

From: fdo-internals-bounces at lists.osgeo.org
[mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Haris
Kurtagic
Sent: Monday, November 17, 2008 5:36 PM
To: FDO Internals Mail List
Subject: [fdo-internals] FDO Function SpatialExtents

 

Hi,

 

I have implemented support for SelectAggregates in King.Oracle.

I am testing SpatialExtent function and I need help in understanding how
clients, MAP 3D , is using it. I am not sure if I understand how is it
supposed to be used.

 

I have implemented function using Oracle SDO_AGGR_MBR. That is rather
slow process .

What I noticed is that MAP 3D 2009 is calling FDO command
SelectAggregates with SpatialExtents function.

That makes rendering of layers very slow in MAP 3D.

 

I know I am asking about non-open source client like MAP 3D but from
what I see makes me wonder if I understand SpatialExtents function
correctly.

 

Thank you,

Haris

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