[postgis-devel] Cube Indexes
schabi at logix-tt.com
Wed Aug 30 02:00:09 PDT 2006
Mark Cave-Ayland wrote:
>> The dimension element is redundant.
>> If we use floats, dim=(size-4)/4 and size=(4*dim)+4, for doubles it is
>> dim=(size-4)/8 and size=(8*dim)+4.
>> For doubles, it may be better to pad to 64 bit offsets on most
>> platforms, and thus keeping the second unsigned int, however.
> Yeah I did consider this at one point, but thought I had come up with a
> reason late one night to show that it wouldn't work when trying to cast
> between BOX3Ds/Geometries... however at the moment I can't see a
> problem, assuming that all of the coordinates are the same size (which
> should be guaranteed in PostGIS).
At least for the storage in the backend, it is guaranteed, and that
format is meant to be internal and architecture-dependent, as PostgreSQL
itsself needs dump/restore for arch and version switches.
SQL Casts between different types need reallocation and copying /
conversion of the data, nevertheless.
Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf. | Software Development GIS
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