split_node_tags: Implement key constraints.

db/migrate/015_key_constraints.rb

@@ -0,0 +1,41 @@
+class KeyConstraints < ActiveRecord::Migration
+  def self.up
+    # Primary keys
+    add_primary_key :current_node_tags, [:id, :k]
+    add_primary_key :current_way_tags, [:id, :k]
+    add_primary_key :current_relation_tags, [:id, :k]
+
+    add_primary_key :node_tags, [:id, :version, :k]
+    add_primary_key :way_tags, [:id, :version, :k]
+    add_primary_key :relation_tags, [:id, :version, :k]
+
+    add_primary_key :nodes, [:id, :version]
+
+    # Foreign keys (between ways, way_tags, way_nodes, etc.)
+    add_foreign_key :current_node_tags, [:id], :current_nodes
+    add_foreign_key :node_tags, [:id, :version], :nodes
+
+    add_foreign_key :current_way_tags, [:id], :current_ways
+    add_foreign_key :current_way_nodes, [:id], :current_ways
+    add_foreign_key :way_tags, [:id, :version], :ways
+    add_foreign_key :way_nodes, [:id, :version], :ways
+
+    add_foreign_key :current_relation_tags, [:id], :current_relations
+    add_foreign_key :current_relation_members, [:id], :current_relations
+    add_foreign_key :relation_tags, [:id, :version], :relations
+    add_foreign_key :relation_members, [:id, :version], :relations
+
+    # Foreign keys (between different types of primitives)
+    add_foreign_key :current_way_nodes, [:node_id], :current_nodes, [:id]
+
+    # FIXME: We don't have foreign keys for relation members since the id
+    # might point to a different table depending on the `type' column.
+    # We'd probably need different current_relation_member_nodes,
+    # current_relation_member_ways and current_relation_member_relations
+    # tables for this to work cleanly.
+  end
+
+  def self.down
+    raise IrreversibleMigration.new
+  end
+end

lib/migrate.rb

@@ -1,6 +1,10 @@
 module ActiveRecord
   module ConnectionAdapters
     module SchemaStatements
+      def quote_column_names(column_name)
+        Array(column_name).map { |e| quote_column_name(e) }.join(", ")
+      end
+
       def add_primary_key(table_name, column_name, options = {})
         column_names = Array(column_name)
         quoted_column_names = column_names.map { |e| quote_column_name(e) }.join(", ")
@@ -11,6 +15,12 @@ module ActiveRecord
         execute "ALTER TABLE #{table_name} DROP PRIMARY KEY"
       end
 
+      def add_foreign_key(table_name, column_name, reftbl, refcol = nil)
+        execute "ALTER TABLE #{table_name} ADD " +
+	  "FOREIGN KEY (#{quote_column_names(column_name)}) " +
+	  "REFERENCES #{reftbl} (#{quote_column_names(refcol || column_name)})"
+      end
+
       alias_method :old_options_include_default?, :options_include_default?
 
       def options_include_default?(options)