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-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
--
-- PostGIS - Spatial Types for PostgreSQL
-- http://postgis.net
--
-- Copyright (C) 2012 Sandro Santilli <strk@kbt.io>
--
-- This is free software; you can redistribute and/or modify it under
-- the terms of the GNU General Public Licence. See the COPYING file.
--
-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-- {
-- Get a simplified geometry version from a TopoGeometry
--
-- Performs Douglas Peucker algorithm on each edge composing
-- the given TopoGeometry
--
-- }{
CREATE OR REPLACE FUNCTION topology.ST_Simplify(tg topology.TopoGeometry, tolerance float8)
RETURNS geometry
AS
$$
DECLARE
topology_info RECORD;
layer_info RECORD;
child_layer_info RECORD;
geom geometry;
sql TEXT;
BEGIN
-- Get topology information
SELECT id, name FROM topology.topology
INTO topology_info
WHERE id = tg.topology_id;
IF NOT FOUND THEN
RAISE EXCEPTION 'No topology with id "%" in topology.topology', tg.topology_id;
END IF;
-- Get layer info
SELECT * FROM topology.layer
WHERE topology_id = tg.topology_id
AND layer_id = tg.layer_id
INTO layer_info;
IF NOT FOUND THEN
RAISE EXCEPTION 'Could not find TopoGeometry layer % in topology %', tg.layer_id, tg.topology_id;
END IF;
--
-- If this feature layer is on any level > 0 we will
-- compute the topological union of all simplified child
-- features in fact recursing.
--
IF layer_info.level > 0 THEN -- {
-- Get child layer info
SELECT * FROM topology.layer WHERE layer_id = layer_info.child_id
AND topology_id = tg.topology_id
INTO child_layer_info;
IF NOT FOUND THEN
RAISE EXCEPTION 'Invalid layer % in topology % (unexistent child layer %)', tg.layer_id, tg.topology_id, layer_info.child_id;
END IF;
sql := 'SELECT st_multi(st_union(topology.ST_Simplify('
|| quote_ident(child_layer_info.feature_column)
|| ',' || tolerance || '))) as geom FROM '
|| quote_ident(child_layer_info.schema_name) || '.'
|| quote_ident(child_layer_info.table_name)
|| ', ' || quote_ident(topology_info.name) || '.relation pr'
|| ' WHERE '
|| ' pr.topogeo_id = ' || tg.id
|| ' AND '
|| ' pr.layer_id = ' || tg.layer_id
|| ' AND '
|| ' id('||quote_ident(child_layer_info.feature_column)
|| ') = pr.element_id '
|| ' AND '
|| 'layer_id('||quote_ident(child_layer_info.feature_column)
|| ') = pr.element_type ';
RAISE DEBUG '%', sql;
EXECUTE sql INTO geom;
ELSIF tg.type = 3 THEN -- [multi]polygon -- }{
-- TODO: use ST_GetFaceEdges
-- TODO: is st_unaryunion needed?
sql := 'SELECT st_multi(st_unaryunion(ST_BuildArea(ST_Node(ST_Collect(ST_Simplify(geom, '
|| tolerance || ')))))) as geom FROM '
|| quote_ident(topology_info.name)
|| '.edge_data e, '
|| quote_ident(topology_info.name)
|| '.relation r WHERE ( e.left_face = r.element_id'
|| ' OR e.right_face = r.element_id )'
|| ' AND r.topogeo_id = ' || tg.id
|| ' AND r.layer_id = ' || tg.layer_id
|| ' AND element_type = 3 ';
RAISE DEBUG '%', sql;
EXECUTE sql INTO geom;
ELSIF tg.type = 2 THEN -- [multi]line -- }{
sql :=
'SELECT st_multi(ST_LineMerge(ST_Node(ST_Collect(ST_Simplify(e.geom,'
|| tolerance || '))))) as g FROM '
|| quote_ident(topology_info.name) || '.edge e, '
|| quote_ident(topology_info.name) || '.relation r '
|| ' WHERE r.topogeo_id = ' || tg.id
|| ' AND r.layer_id = ' || tg.layer_id
|| ' AND r.element_type = 2 '
|| ' AND abs(r.element_id) = e.edge_id';
EXECUTE sql INTO geom;
ELSIF tg.type = 1 THEN -- [multi]point -- }{
-- Can't simplify points...
geom := topology.Geometry(tg);
ELSIF tg.type = 4 THEN -- mixed collection -- }{
sql := 'WITH areas AS ( '
|| 'SELECT st_multi(st_union(ST_BuildArea(ST_Node(ST_Collect(ST_Simplify(geom, '
|| tolerance || ')))) as geom FROM '
|| quote_ident(topology_info.name)
|| '.edge_data e, '
|| quote_ident(topology_info.name)
|| '.relation r WHERE ( e.left_face = r.element_id'
|| ' OR e.right_face = r.element_id )'
|| ' AND r.topogeo_id = ' || tg.id
|| ' AND r.layer_id = ' || tg.layer_id
|| ' AND element_type = 3 ), '
|| 'lines AS ( '
|| 'SELECT st_multi(ST_LineMerge(ST_Collect(ST_Simplify(e.geom,'
|| tolerance || ')))) as g FROM '
|| quote_ident(topology_info.name) || '.edge e, '
|| quote_ident(topology_info.name) || '.relation r '
|| ' WHERE r.topogeo_id = ' || tg.id
|| ' AND r.layer_id = ' || tg.layer_id
|| ' AND r.element_type = 2 '
|| ' AND abs(r.element_id) = e.edge_id ), '
|| ' points as ( SELECT st_union(n.geom) as g FROM '
|| quote_ident(topology_info.name) || '.node n, '
|| quote_ident(topology_info.name) || '.relation r '
|| ' WHERE r.topogeo_id = ' || tg.id
|| ' AND r.layer_id = ' || tg.layer_id
|| ' AND r.element_type = 1 '
|| ' AND r.element_id = n.node_id ), '
|| ' un as ( SELECT g FROM areas UNION ALL SELECT g FROM lines '
|| ' UNION ALL SELECT g FROM points ) '
|| 'SELECT ST_Multi(ST_Collect(g)) FROM un';
EXECUTE sql INTO geom;
ELSE -- }{
RAISE EXCEPTION 'Invalid TopoGeometries (unknown type %)', tg.type;
END IF; -- }
RETURN geom;
END
$$
LANGUAGE 'plpgsql' VOLATILE STRICT;
-- }
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