WL#7541: GIS MBR spatial operations enhancement
Status: Complete — Priority: Medium
MBR operations for GIS is very essential, existing GIS MBR support is mostly OK, although there are things that can be improved, issues I've found currently including: 1. Some mbr functions are wired to the wrong Item_func, including 'mbrtouches', and 'touches', which are implemented not using a geometry's mbr but using the geometry itself. 2. Fix mbrwithin/mbrtouches, they didn't return correct results when one or both mbrs degrade to a point/line segment. 3. We need a few new MBR relation check functions.
F-1: MBRTOUCHES function should do the 'touches' spatial relation checking using two geometries' MBR boxes, not using the geometry itself. F-2: Fix mbrtouches and mbrwithin bugs: they returned wrong results when one or both of the mbr arguments degrade to a point or horizontal/vertical line segment. Fix the bugs according to OGC definition for touches and within. With changes of this WL applied, when a point lies on the boundary of a line segment or polygon, or when a line segment lies totally on the boundary of a polygon, it's not considered 'within' but 'touches' instead; and two identical points will not be considered 'touches' with changes of this WL applied. F-3: Add 'mbrequals' as another name for 'mbrequal', because we have 'equals' and 'st_equals', but 'mbrequal' doesn't follow the same naming convention. And also deprecate mbrequal. F-4: Add 'mbrcoveredby', and 'mbrcovers' GEOM_1 MBRCOVERS GEOM_2 if any only if the MBR of GEOM_2 lies within or on the boarder of the MBR of GEOM_1; The DE-9IM definition for COVERS is: (II AND ~EI AND ~EB) OR (IB AND ~EI AND ~EB) OR (BI AND ~EI AND ~EB) OR (BB AND ~EI AND ~EB) and the two checks are opposite: GEOM_1 MBRCOVERS GEOM2 <=> GEOM_2 MBRCOVEREDBY GEOM_1 F-5: MBRCOVERS and MBRCOVEREDBY MUST return NULL if either argument is NULL or an empty geometry; F-6: MBRCOVERS and MBRCOVEREDBY MUST NOT return NULL if neither arguments are NULL or empty geometry. F-7: MBRCOVERS and MBRCOVEREDBY MAY allow invalid geometry arguments, the invalidity is according to OGC specifications. F-8: MBRCOVERS and MBRCOVEREDBY SHOULD report ER_GIS_INVALID_DATA if either arguments are not valid GEOMETRY byte string. and they SHOULD not report any other error.
Changes to the interface specification: I-1: No new files. I-2: New syntax: Two new functions:
= MBRCOVEREDBY( , ); = MBRCOVERS( , ); Here the is a byte string of GEOMETRY (SRID+WKB) format. I-3: No new commands. I-4: No new tools. I-5: No impact on existing functionality.
1. Wire up mbrtouches to Item_func_spatial_mbr_rel to call MBR::touches. 2. Add creators for the two new GIS functions of F-4. 3. Implement the two new GIS functions according to F-4 ~ F-8. 4. Fix bugs of MBR::within and MBR::touches, basically they need to consider degraded polygon --- a point, or a vertical/horizontal line segment.
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