[UMN_MAPSERVER-USERS] Question re: PostGIS and MapScript getExtent() function

Fernando Simon fsimon at UNIVALI.BR
Wed Jul 13 10:30:45 EDT 2005

    I don't know if this issue occur in PostGIS, but sometimes when the 
source of the data is a spatial function(buffer, centroid, union, 
xor...) or a complex query (select with subselects and subselects...) 
the Oracle Spatial don't create a spatial index for the data, so for 
Oracle Spatial the function for fast Extent will return a database error 
and can crash or don't return any correct value for Mapserv. Is it occur 
in PostGIS?

Fernando Simon
Mapserver and Oracle Spatial developer
G10 - Laboratorio de Computacao Aplicada - Brazil
http://g10.cttmar.univali.br - UNIVALI/CTTMAR

Daniel Morissette wrote:

> Paul Ramsey wrote:
>> Steve,
>> Try it on a 20M record table in Oracle. Both implementations,  
>> Oracle's and your uncommented PostGIS one, do the same functional  
>> thing, which is a full table scan.  It is possible that Oracle is  
>> slightly smarter about reading the index for the AGGR_MBR case, 
>> which  might make it work better on large tables: one for the testing 
>> range.
> Since you guys wrote all the indexing code in postgis, would you not 
> be able to add a function to fetch the real data extents from the 
> index somehow? That would give fast and accurate responses all the 
> time. Is this information not available in the data structures somewhere?
> Daniel

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