Changes between Version 13 and Version 14 of DevWikiEmptyGeometry


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Timestamp:
Oct 6, 2009, 12:26:57 PM (15 years ago)
Author:
chodgson
Comment:

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  • DevWikiEmptyGeometry

    v13 v14  
    11The semantics of NULL are well defined for us already in SQL standards. However, in the world of Geometry / Geography we have another entity which is not quite NULL nor quite fully defined: the empty geometry. Empty geometries can be created with things like intersection calls that have have no intersection, e.g. ST_Intersect('POINT(0 0)', 'POINT(1 1)') == POINT EMPTY. So, in the presence of empty, how should functions behave?
     2
     3Ideally ''GEOMETRY EMPTY'' should behave more like 'zero' (0) than NULL - it is an expected, valid result of a successful, valid operation. In other words, dealing with ''EMPTY'' should require as little "special case" handling as possible in logical expressions making use of multiple geometry operations and/or comparisons. Maintaining compatibility with other spatial databases is probably valuable in its own right, and also because they have probably already done some thinking around these issues.
    24
    35 * ST_Union(geometry, empty) == geometry