Description

Drop the bounding box cache from the geometry. This reduces geometry size, but makes bounding-box based queries slower. It is also used to drop a corrupt bounding box. A tale-tell sign of a corrupt cached bounding box is when your ST_Intersects and other relation queries leave out geometries that rightfully should return true.

Bounding boxes are automatically added to geometries and improve speed of queries so in general this is not needed unless the generated bounding box somehow becomes corrupted or you have an old install that is lacking bounding boxes. Then you need to drop the old and re-add. This kind of corruption has been observed in 8.3-8.3.6 series whereby cached bboxes were not always recalculated when a geometry changed and upgrading to a newer version without a dump reload will not correct already corrupted boxes. So one can manually correct using below and re-add the bbox or do a dump reload.

This method supports Circular Strings and Curves.

Examples

This example drops cached bounding boxes where the stored box is wrong. Applying Box2D to ST_AsBinary forces a fresh box calculation, while Box2D on the table geometry reads the cached box.

UPDATE sometable
SET geom =  PostGIS_DropBBox(geom)
WHERE Not (Box2D(ST_AsBinary(geom)) = Box2D(geom));

UPDATE ...

After dropping corrupt cached boxes, re-add them where needed.

UPDATE sometable
SET geom =  PostGIS_AddBBox(geom)
WHERE Not PostGIS_HasBBOX(geom);

UPDATE ...

See Also

PostGIS_AddBBox, PostGIS_HasBBox, Box2D