[postgis-users] Documenting performance tip

[Markus Schaber]

Hi, Strk,

strk at refractions.net schrieb:
> Markus, thanks for the insight.
> A side-effect of your suggestion is that users will end up
> actually using box2d type in their tables.
> I think they should be warned that those column won't retain
> their original precision between dump/reloads.
> More so now that box2d canonical ascii output has been changed
> to use default precision (%g).
> What do you think ?

Exactly for this reason, I actually try to store a geometry in the column.

SELECT addGeometryColumn('mydb','mytable','bbox','4326','GEOMETRY','2');
UPDATE mytable set bbox = setsrid(box3d(geom_column)::geometry, 4326);

That creates a "geometry" column and inserts a box3d back-casted to
geometry into it. PostGIS 1.0 stores a POLYGON with 5 Ordinates, while
PostGIS 0.8.1 stores something that ouputs as "SRID=4326;BOX3D(...)"
although the column is of type geometry. Both should be without loss.

Markus



--
markus schaber | dipl. informatiker
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