From aa0927911df5dd919e32b5df282d96c956d7176a Mon Sep 17 00:00:00 2001
From: Emil Tin <emil.tin@tmf.kk.dk>
Date: Fri, 18 Oct 2013 18:24:13 +0200
Subject: [PATCH] example showing use of PostGIS data

---
 profiles/examples/postgis.lua | 82 +++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 profiles/examples/postgis.lua

diff --git a/profiles/examples/postgis.lua b/profiles/examples/postgis.lua
new file mode 100644
index 000000000..6728c8abf
--- /dev/null
+++ b/profiles/examples/postgis.lua
@@ -0,0 +1,82 @@
+
+-- This example shows how to query external data stored in PostGIS when processing ways.
+
+-- This profile assumes that OSM data has been imported to PostGIS using imposm to a db
+-- with the name 'imposm', the default user and no password. It assumes  areas with
+-- landusage=* was imported to the table osm_landusages, containting the columns type and area.
+-- Seee http://imposm.org/ for more info on imposm.
+-- Other tools for importing OSM data to PostGIS include osm2pgsql and osmosis.
+
+-- It uses the PostGIS function ST_DWithin() to find areas tagged with landuse=industrial
+-- that are within 100 meters of the way.
+-- It then slows down the routing depending on the number and size of the industrial area.
+
+-- The end result is that routes will tend to avoid industrial area. Passing through
+-- industrial areas is still possible, it's just slower, and thus avoided if a reasonable
+-- alternative is found.
+
+-- We use the osm id as the key when querying PostGIS. Be sure to add an index to the colunn
+-- containing the osm id (osm_id in this case), otherwise you will suffer form very
+-- bad performance. You should also have spatial indexes on the relevant gemoetry columns.
+
+-- More info about using SQL form LUA can be found at http://www.keplerproject.org/luasql/
+
+-- Happy routing!
+
+
+-- Open PostGIS connection
+lua_sql = require "luasql.postgres"           -- we will connect to a postgresql database
+sql_env = assert( lua_sql.postgres() )
+sql_con = assert( sql_env:connect("imposm") ) -- you can add db user/password here if needed
+print("PostGIS connection opened")
+
+-- these settings are read directly by osrm
+take_minimum_of_speeds 	= true
+obey_oneway 			      = true
+obey_bollards 			    = true
+use_restrictions 		    = true
+ignore_areas 			      = true	-- future feature
+traffic_signal_penalty 	= 7		  -- seconds
+u_turn_penalty 			    = 20
+
+-- nodes processing, called from OSRM
+function node_function(node)
+  return 1
+end
+
+-- ways processing, called from OSRM
+function way_function (way)
+  -- only route on ways with highway=*
+	local highway = way.tags:Find("highway")
+	if (not highway or highway=='') then
+	  return 0
+  end
+
+	-- Query PostGIS for industrial areas close to the way, then groups by way and sums the areas.
+  -- We take the square root of the area to get a estimate of the length of the side of the area, 
+  -- and thus a rough guess of how far we might be travelling along the area. 
+	
+	local sql_query = " " ..
+    "SELECT SUM(SQRT(area.area)) AS val " ..
+    "FROM osm_ways way " ..
+    "LEFT JOIN osm_landusages area ON ST_DWithin(way.geometry, area.geometry, 100) " ..
+    "WHERE area.type IN ('industrial') AND way.osm_id=" .. way.id .. " " ..
+    "GROUP BY way.id"
+  
+  local cursor = assert( sql_con:execute(sql_query) )   -- execute querty
+  local row = cursor:fetch( {}, "a" )                   -- fetch first (and only) row
+  way.speed = 20.0                                      -- default speed
+  if row then
+    local val = tonumber(row.val)                       -- read 'val' from row 
+    if val > 10 then
+      way.speed = way.speed / math.log10( val )         -- reduce speed by amount of industry close by 
+    end
+  end
+  cursor:close()                                        -- done with this query
+  
+  -- set other required info for this way
+ 	way.name = way.tags:Find("name")
+	way.direction = Way.bidirectional 
+	way.type = 1
+	return 1
+end