Commit a4ce1e04 authored by Sandro Santilli's avatar Sandro Santilli
Browse files

Rewrite topology.GetRingEdges using a recursive CTE (#2087) 

Walking around a ring of ~22k edges takes 1/7 of the time

git-svn-id: http://svn.osgeo.org/postgis/trunk@10660 b70326c6-7e19-0410-871a-916f4a2858ee
parent 6eaadd1f

topology/sql/query/GetRingEdges.sql.in.c

+16 −41
Original line number Diff line number Diff line
@@ -3,7 +3,7 @@ 
-- PostGIS - Spatial Types for PostgreSQL

-- http://postgis.refractions.net

--

-- Copyright (C) 2011 Sandro Santilli <strk@keybit.net>

-- Copyright (C) 2011 2012 Sandro Santilli <strk@keybit.net>

--

-- This is free software; you can redistribute and/or modify it under

-- the terms of the GNU General Public Licence. See the COPYING file.
@@ -42,56 +42,31 @@ CREATE OR REPLACE FUNCTION topology.GetRingEdges(atopology varchar, anedge int, 
AS

$$

DECLARE

  curedge int;

  nextedge int;

  rec RECORD;

  bounds geometry;

  retrec topology.GetFaceEdges_ReturnType;

  n int;

  sql text;

BEGIN

  sql := 'WITH RECURSIVE edgering AS ( SELECT '

    || anedge

    || ' as signed_edge_id, edge_id, next_left_edge, next_right_edge FROM '

    || quote_ident(atopology)

    || '.edge_data WHERE edge_id = '

    || abs(anedge)

    || ' UNION '

    || ' SELECT CASE WHEN p.signed_edge_id < 0 THEN p.next_right_edge '

    || ' ELSE p.next_left_edge END, e.edge_id, e.next_left_edge, e.next_right_edge '

    || ' FROM ' || quote_ident(atopology)

    || '.edge_data e, edgering p WHERE e.edge_id = CASE WHEN p.signed_edge_id < 0 '

    || 'THEN abs(p.next_right_edge) ELSE abs(p.next_left_edge) END ) SELECT * FROM edgering';



  curedge := anedge;

  n := 1;



  WHILE true LOOP

    sql := 'SELECT edge_id, next_left_edge, next_right_edge FROM '

      || quote_ident(atopology) || '.edge_data WHERE edge_id = '

      || abs(curedge);

    EXECUTE sql INTO rec;

  FOR rec IN EXECUTE sql

  LOOP

    retrec.sequence := n;

    retrec.edge := curedge;



#ifdef POSTGIS_TOPOLOGY_DEBUG

    RAISE DEBUG 'Edge:% left:% right:%',

      curedge, rec.next_left_edge, rec.next_right_edge;

#endif



    retrec.edge := rec.signed_edge_id;

    RETURN NEXT retrec;



    IF curedge < 0 THEN

      nextedge := rec.next_right_edge;

    ELSE

      nextedge := rec.next_left_edge;

    END IF;



    IF nextedge = anedge THEN

#ifdef POSTGIS_TOPOLOGY_DEBUG

      RAISE DEBUG ' finish';

#endif

      RETURN;

    END IF;



    IF nextedge = curedge THEN

      RAISE EXCEPTION 'Detected bogus loop traversing edge %', curedge;

    END IF;



    curedge := nextedge;



#ifdef POSTGIS_TOPOLOGY_DEBUG

    RAISE DEBUG ' curedge:% anedge:%', curedge, anedge;

#endif



    n := n + 1;



    IF n > maxedges THEN