(sql/separateTouching) Adding new function separateTouching

Author: cvvergara

sql/sigs/pgrouting--3.8.sig

@@ -266,6 +266,7 @@ pgr_pushrelabel(text,bigint,bigint)
 pgr_pushrelabel(text,text)
 _pgr_quote_ident(text)
 pgr_separatecrossing(text,double precision,boolean)
+pgr_separatetouching(text,double precision,boolean)
 _pgr_sequentialvertexcoloring(text)
 pgr_sequentialvertexcoloring(text)
 _pgr_startpoint(geometry)

sql/utilities/CMakeLists.txt

@@ -2,6 +2,7 @@
 SET(LOCAL_FILES
     findCloseEdges.sql
     separateCrossing.sql
+    separateTouching.sql
     )
 
 foreach (f ${LOCAL_FILES})

sql/utilities/separateTouching.sql

@@ -0,0 +1,115 @@
+/*PGR-GNU*****************************************************************
+File: separateTouching.sql
+
+Copyright (c) 2025 pgRouting developers
+Mail: [email protected]
+
+Copyright (c) 2025 Celia Virginia Vergara Castillo
+Mail: vicky at erosion.dev
+
+------
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+ ********************************************************************PGR-GNU*/
+
+--v3.8
+CREATE FUNCTION pgr_separateTouching(
+  TEXT, -- edges SQL
+  tolerance FLOAT DEFAULT 0.01, -- tolerance
+  dryrun BOOLEAN DEFAULT false,
+
+  OUT seq INTEGER,
+  OUT id BIGINT,
+  OUT sub_id INTEGER,
+  OUT geom geometry)
+RETURNS SETOF RECORD AS
+$BODY$
+DECLARE
+  edges_sql TEXT := $1;
+
+  the_query TEXT;
+  sqlhint TEXT;
+  has_geom BOOLEAN;
+  has_id BOOLEAN;
+BEGIN
+
+  BEGIN
+    edges_sql := _pgr_checkQuery($1);
+    EXCEPTION WHEN OTHERS THEN
+      GET STACKED DIAGNOSTICS sqlhint = PG_EXCEPTION_HINT;
+      RAISE EXCEPTION '%', SQLERRM USING HINT = sqlhint, ERRCODE = SQLSTATE;
+  END;
+
+  has_id := _pgr_checkColumn(edges_sql, 'id', 'ANY-INTEGER', true, dryrun => $3);
+  has_geom := _pgr_checkColumn(edges_sql, 'geom', 'geometry', true, dryrun => $3);
+
+  the_query := format($$
+    WITH
+    edges_table AS (
+      %s
+    ),
+
+    get_touching AS (
+      SELECT e1.id id1, e2.id id2, ST_Snap(e1.geom, e2.geom, %2$s) AS geom, e1.geom AS g1, e2.geom AS g2
+      FROM edges_table e1, edges_table e2
+      WHERE e1.id != e2.id AND ST_DWithin(e1.geom, e2.geom, %2$s) AND NOT(
+        ST_StartPoint(e1.geom) = ST_StartPoint(e2.geom) OR ST_StartPoint(e1.geom) = ST_EndPoint(e2.geom)
+        OR ST_EndPoint(e1.geom) = ST_StartPoint(e2.geom) OR ST_EndPoint(e1.geom) = ST_EndPoint(e2.geom))
+    ),
+
+    touchings AS (
+      SELECT  id1, g1, g2, st_intersection(geom, g2) AS point
+      FROM get_touching
+      WHERE  NOT (geom = g1)
+    ),
+
+    blades AS (
+      SELECT id1, g1, ST_UnaryUnion(ST_Collect(point)) AS blade
+      FROM touchings
+      GROUP BY id1, g1
+    ),
+
+    collection AS (
+      SELECT id1, (st_dump(st_split(st_snap(g1, blade, %2$s), blade))).*
+      FROM blades
+    )
+
+    SELECT row_number() over()::INTEGER AS seq, id1::BIGINT, path[1], geom
+    FROM collection;
+    $$,
+
+    edges_sql, tolerance);
+
+    IF dryrun THEN
+      RAISE NOTICE '%', the_query || ';';
+    ELSE
+      RETURN QUERY EXECUTE the_query;
+    END IF;
+
+END;
+$BODY$ LANGUAGE 'plpgsql' VOLATILE STRICT;
+
+-- COMMENTS
+COMMENT ON FUNCTION pgr_separateTouching(TEXT, FLOAT, BOOLEAN)
+IS 'pgr_separateTouching
+- Parameters
+  - Edges SQL with columns: id, geom
+- Optional parameters
+  - tolerance => 0.01
+  - dryrun => true
+- DOCUMENTATION:
+  - ${PROJECT_DOC_LINK}/pgr_separateTouching.html
+';