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Applying and Extending Oracle Spatial by Siva Ravada, Simon Gerard Greener

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Extending a linestring

The requirement to extend a linestring is quite common in the world of a practitioner. This can be done by coding a single ST_Extend member function. The rules that will govern this function are:

  • Operates only on linestrings
  • Allows for shortening via provision of a negative extension distance
  • Can be applied to the start, end, or both ends at the same time
  • Negative extension distances that could collapse the linestring to nothing need to be captured

The function's declaration in the T_Geometry type is as follows:

Create Or Replace TYPE T_Geometry As Object (
[...]
  Member Function
  ST_Extend(p_extend_dist In number,
            p_start_end   In varchar2 default 'START',
            p_unit        In varchar2 default null)
     Return T_Geometry Deterministic,

The ST_Extend ...

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