Syntax

   FACTORY_DEF <ReaderKeyword> SortFactory
   [FACTORY_NAME <factory name>] 
   [INPUT FEATURE_TYPE <feature type>
      [<attribute name> <attribute value>]*
      [<feature function>]*]*
   [GROUP_BY [<attribute name>]+]*
   [FLUSH_WHEN_GROUPS_CHANGE (Yes|No)]
   [SORT_BY [<attribute name> (NUMERIC|ALPHA)
      [(ASCENDING|DESCENDING)]]+]
   [SORT_DIRECTION (ASCENDING|DESCENDING)]
   [GEOMETRY_SORT_METHOD (HILBERT_2D|HILBERT_3D)]
   [MEMORY_CACHE_SIZE <number>]
   [OUTPUT SORTED FEATURE_TYPE <feature type> 
      [<attribute name> <attribute value>]* 
      [<feature function>]*]*

Overview

   This factory sorts features according to the values of the specified 
   attributes, as determined by the factory definition. For each attribute name, 
   directions are given about how its value should be interpreted when it is 
   compared. If NUMERIC is specified, then numeric comparisons will be done. If 
   ALPHA is specified, then alphanumeric comparisons will be done. If no SORT_BY 
   clause is specified, then the SortFactory will hold all features that enter 
   the factory until all other features have passed. Then it will release the 
   features into the factory pipeline. This is useful if, for example, you want 
   to detain certain features until all input features have arrived, thereby 
   ensuring that no additional processing is performed.

   Once the factory is told to empty itself, it outputs all features it received 
   in the order specified. Any SORT_BY clause that does not specify ASCENDING or 
   DESCENDING will use the direction specified by SORT_DIRECTION. That is, the 
   per-attribute sort direction overrides the global sort direction. By default, 
   the SORT_DIRECTION is in ascending order.

   If the GEOMETRY_SORT_METHOD clause is present, this means the factory will
   sort the geometries by their Geometry, using Hilbert sorting (either in 2D or 3D).
   All of the parameters for attribute sorting will be ignored.
     - The centroid of the bounding box (2D or 3D) is used for sorting.
     - If 3D mode is selected, 2D geometries will assume a z value of 0.0 for sorting.


   This factory tries to balance speed and memory usage by storing some features 
   in memory and some in a temporary disk file. The maximum number of features 
   stored in memory can be set using the MEMORY_CACHE_SIZE clause. If this is 
   not explicitly set, the default value used is 100.

   If an attribute name is specified but is not present on a feature, then the 
   sorting algorithm will consider that feature to have a null or zero value for 
   that attribute.

   An O(nlogn) algorithm is used to do the sorting.

Parameters

   GROUP_BY

      This clause allows for processing features in groups based on one or more
      attributes on the input features. Processing will only be performed on input
      features whose group by attributes (as specified by this clause) are identical.

   FLUSH_WHEN_GROUPS_CHANGE

      If the GROUP_BY clause is specified, this clause (when set to Yes) will cause
      the factory to process and output the current group immediately when an
      attribute that does not belong to the current group is encountered.

Output Tags

   The SortFactory supports the following output tag.
   
   SORTED   
   
      Applied to all features that leave this factory.