ST_BuildPyramidUseGeomSideLen-ApsaraDB RDS(RDS)-阿里云帮助中心

This topic describes the ST_BuildPyramidUseGeomSideLen function. This function builds a pyramid if the original vector table has a column that records the length of the bounding box of vector data, and an index is created for this column. For example, a B-tree index is created. Compared with the ST_BuildPyramid function, the ST_BuildPyramidUseGeomSideLen function significantly improves the efficiency to build and update pyramids.

Syntax

boolean ST_BuildPyramidUseGeomSideLen(cstring table, cstring geom_field, cstring geom_side_len_field, cstring fid, cstring config);

Parameters

Parameter Name	Description
table	The name of the spatial geometry table.
geom_field	The name of the geometry field.
geom_side_len_field	The name of the field that records the maximum side length of the bounding box for the geometry in the geom_field column.
fid	The name of the feature ID field.
config	Parameters to create the pyramid.

The definition of the config parameter is the same as that in ST_BuildPyramid.

Examples

ALTER TABLE roads
ADD COLUMN geom_side_len DOUBLE PRECISION;
CREATE OR REPLACE FUNCTION add_max_len_values() RETURNS VOID AS $$
DECLARE
  t_curs CURSOR FOR
    SELECT * FROM roads;
  t_row test_polygon_geom_side_len%ROWTYPE;
  gm GEOMETRY;
  x_min DOUBLE PRECISION;
  x_max DOUBLE PRECISION;
  y_min DOUBLE PRECISION;
  y_max DOUBLE PRECISION;
BEGIN
  FOR t_row IN t_curs LOOP
    SELECT t_row.geom INTO gm;
    SELECT ST_XMin(gm) INTO x_min;
    SELECT ST_XMax(gm) INTO x_max;
    SELECT ST_YMin(gm) INTO y_min;
    SELECT ST_YMax(gm) INTO y_max;
    UPDATE roads
      SET geom_side_len = GREATEST(x_max - x_min, y_max - y_min)
    WHERE CURRENT OF t_curs;
  END LOOP;
END;
$$ LANGUAGE plpgsql;
SELECT add_max_len_values();
CREATE INDEX ON roads USING btree(geom_side_len);

SELECT ST_BuildPyramidUseGeomSideLen('roads', 'geom', 'geom_side_len', 'id',
  '{"parallel":4}');