Replace hard coded nwr enumeration support with a more generic

system for defining enumerations.

db/migrate/007_add_relations.rb

@@ -2,18 +2,19 @@ require 'lib/migrate'
 
 class AddRelations < ActiveRecord::Migration
   def self.up
+    # enums work like strings but are more efficient
+    create_enumeration :nwr_enum, ["Node", "Way", "Relation"]
+
     # a relation can have members much like a way can have nodes.
     # differences:
     # way: only nodes / relation: any kind of member
     # way: ordered sequence of nodes / relation: free-form "role" string
     create_table "current_relation_members", innodb_table do |t|
-      t.column "id",          :bigint, :limit => 64, :null => false
-      t.column "member_type", :string, :limit => 11, :null => false
-      t.column "member_id",   :bigint, :limit => 11, :null => false
+      t.column "id",          :bigint,   :limit => 64, :null => false
+      t.column "member_type", :nwr_enum, :null => false
+      t.column "member_id",   :bigint,   :limit => 11, :null => false
       t.column "member_role", :string
     end
-    # enums work like strings but are more efficient
-    alter_column_nwr_enum :current_relation_members, :member_type
 
     add_primary_key "current_relation_members", ["id", "member_type", "member_id", "member_role"]
     add_index "current_relation_members", ["member_type", "member_id"], :name => "current_relation_members_member_idx"
@@ -36,14 +37,13 @@ class AddRelations < ActiveRecord::Migration
     end
 
     create_table "relation_members", myisam_table do |t|
-      t.column "id",          :bigint,  :limit => 64, :default => 0, :null => false
-      t.column "member_type", :string, :limit => 11, :null => false
-      t.column "member_id",   :bigint, :limit => 11, :null => false
+      t.column "id",          :bigint,   :limit => 64, :default => 0, :null => false
+      t.column "member_type", :nwr_enum, :null => false
+      t.column "member_id",   :bigint,   :limit => 11, :null => false
       t.column "member_role", :string
-      t.column "version",     :bigint,  :limit => 20, :default => 0, :null => false
+      t.column "version",     :bigint,   :limit => 20, :default => 0, :null => false
     end
 
-    alter_column_nwr_enum :relation_members, :member_type 
     add_primary_key "relation_members", ["id", "version", "member_type", "member_id", "member_role"]
     add_index "relation_members", ["member_type", "member_id"], :name => "relation_members_member_idx"
 
@@ -78,5 +78,6 @@ class AddRelations < ActiveRecord::Migration
     drop_table :current_relation_tags
     drop_table :relation_members
     drop_table :current_relation_members
+    drop_enumeration :nwr_enum
   end
 end

lib/migrate.rb

@@ -59,6 +59,11 @@ module ActiveRecord
         types[:bigint_auto_20] = { :name => "bigint(20) DEFAULT NULL auto_increment" }
         types[:four_byte_unsigned] = { :name=> "integer unsigned" }
         types[:inet] = { :name=> "integer unsigned" }
+
+        enumerations.each do |e,v|
+          types[e.to_sym]= { :name => "enum('#{v.join '\',\''}')" }
+        end
+
         types
       end
 
@@ -96,8 +101,16 @@ module ActiveRecord
         execute "CREATE FULLTEXT INDEX `#{table_name}_#{column}_idx` ON `#{table_name}` (`#{column}`)"
       end
 
-      def alter_column_nwr_enum (table_name, column)
-        execute "alter table #{table_name} change column #{column} #{column} enum('Node','Way','Relation');"
+      def enumerations
+        @enumerations ||= Hash.new
+      end
+
+      def create_enumeration (enumeration_name, values)
+        enumerations[enumeration_name] = values
+      end
+
+      def drop_enumeration (enumeration_name)
+        enumerations.delete(enumeration_name)
       end
 
       def alter_primary_key(table_name, new_columns)
@@ -125,6 +138,11 @@ module ActiveRecord
         types[:bigint_auto_20] = { :name => "bigint" } #fixme: need autoincrement?
         types[:four_byte_unsigned] = { :name => "bigint" } # meh
         types[:inet] = { :name=> "inet" }
+
+        enumerations.each_key do |e|
+          types[e.to_sym]= { :name => e }
+        end
+
         types
       end
 
@@ -147,13 +165,18 @@ module ActiveRecord
         execute "CREATE INDEX #{table_name}_#{column}_idx on #{table_name} (#{column})"
       end
 
-      def alter_column_nwr_enum (table_name, column)
-        response = select_one("select count(*) as count from pg_type where typname = 'nwr_enum'")
-        if response['count'] == "0" #yep, as a string
-          execute "create type nwr_enum as ENUM ('Node', 'Way', 'Relation')"
-        end
-        execute	"alter table #{table_name} drop #{column}"
-        execute "alter table #{table_name} add #{column} nwr_enum"
+      def enumerations
+        @enumerations ||= Hash.new
+      end
+
+      def create_enumeration (enumeration_name, values)
+        enumerations[enumeration_name] = values
+        execute "create type #{enumeration_name} as enum ('#{values.join '\',\''}')"
+      end
+
+      def drop_enumeration (enumeration_name)
+        execute "drop type #{enumeration_name}"
+        enumerations.delete(enumeration_name)
       end
 
       def alter_primary_key(table_name, new_columns)