Only use the db functions for migrations if USE_DB_FUNCTIONS is set

in the environment. This could possibly be revisited when we move to
rails 2.3 by using a nested transaction to try the function without
causing the surrounding transaction to abort.

db/migrate/005_tile_tracepoints.rb

@@ -6,9 +6,9 @@ class TileTracepoints < ActiveRecord::Migration
     add_index "gps_points", ["tile"], :name => "points_tile_idx"
     remove_index "gps_points", :name => "points_idx"
 
-    begin
+    if ENV["USE_DB_FUNCTIONS"]
       Tracepoint.update_all("latitude = latitude * 10, longitude = longitude * 10, tile = tile_for_point(latitude * 10, longitude * 10)")
-    rescue ActiveRecord::StatementInvalid => ex
+    else
       Tracepoint.find(:all).each do |tp|
         tp.latitude = tp.latitude * 10
         tp.longitude = tp.longitude * 10

db/migrate/006_tile_nodes.rb

@@ -2,7 +2,7 @@ require 'lib/migrate'
 
 class TileNodes < ActiveRecord::Migration
   def self.upgrade_table(from_table, to_table, model)
-    begin
+    if ENV["USE_DB_FUNCTIONS"]
       execute <<-END_SQL
       INSERT INTO #{to_table} (id, latitude, longitude, user_id, visible, tags, timestamp, tile)
       SELECT id, ROUND(latitude * 10000000), ROUND(longitude * 10000000),
@@ -11,7 +11,7 @@ class TileNodes < ActiveRecord::Migration
                             CAST(ROUND(longitude * 10000000) AS INTEGER))
       FROM #{from_table}
       END_SQL
-    rescue ActiveRecord::StatementInvalid => ex
+    else
       execute <<-END_SQL
       INSERT INTO #{to_table} (id, latitude, longitude, user_id, visible, tags, timestamp, tile)
       SELECT id, ROUND(latitude * 10000000), ROUND(longitude * 10000000),