# Exceptional Functions

These functions are rarely used functions that should only be used if your data is corrupted in someway. They are used for troubleshooting corruption and also fixing things that should under normal circumstances, never happen.

PostGIS_AddBBox

Add bounding box to the geometry.

    				geometry PostGIS_AddBBox
    				geometry  geomA

### Description

Add bounding box to the geometry. This would make bounding box based queries faster, but will increase the size of the geometry.

Bounding boxes are automatically added to geometries 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 readd.

&curve_support;

### Examples

    UPDATE sometable
     SET geom =  PostGIS_AddBBox(geom)
     WHERE PostGIS_HasBBox(geom) = false;

### See Also

PostGIS_DropBBox, PostGIS_HasBBox

PostGIS_DropBBox

Drop the bounding box cache from the geometry.

    				geometry PostGIS_DropBBox
    				geometry  geomA

### 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 readd. 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 readd the bbox or do a dump reload.

&curve_support;

### Examples

    --This example drops bounding boxes where the cached box is not correct
    			--The force to ST_AsBinary before applying Box2D forces a recalculation of the box, and Box2D applied to the table geometry always
    			-- returns the cached bounding box.
    			UPDATE sometable
     SET geom =  PostGIS_DropBBox(geom)
     WHERE Not (Box2D(ST_AsBinary(geom)) = Box2D(geom));

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

### See Also

PostGIS_AddBBox, PostGIS_HasBBox, Box2D

PostGIS_HasBBox

Returns TRUE if the bbox of this geometry is cached, FALSE otherwise.

    			boolean PostGIS_HasBBox
    			geometry  geomA

### Description

Returns TRUE if the bbox of this geometry is cached, FALSE otherwise. Use PostGIS_AddBBox and PostGIS_DropBBox to control caching.

&curve_support;

### Examples

    SELECT geom
    FROM sometable WHERE PostGIS_HasBBox(geom) = false;

### See Also

PostGIS_AddBBox, PostGIS_DropBBox