Modify column types and names, forcing the typecast

app/controllers/api/json/tables_controller.rb

@@ -131,13 +131,15 @@ class Api::Json::TablesController < ApplicationController
   def update_schema
     respond_to do |format|
       format.json do
-        if params[:what] && %W{ add drop }.include?(params[:what])
+        if params[:what] && %W{ add drop modify }.include?(params[:what])
           unless params[:column].blank? || params[:column].empty?
             begin
               if params[:what] == 'add'
                 @table.add_column!(params[:column])
-              else
+              elsif params[:what] == 'drop'
                 @table.drop_column!(params[:column])
+              else
+                @table.modify_column!(params[:column])
               end
               render :nothing => true, :status => 200
             rescue => e

app/models/table.rb

@@ -122,6 +122,30 @@ class Table < Sequel::Model(:user_tables)
     end
   end
 
+  def modify_column!(options)
+    owner.in_database do |user_database|
+      if options[:old_name] && options[:new_name]
+        user_database.rename_column name.to_sym, options[:old_name].to_sym, options[:new_name].to_sym
+      end
+      if options[:type]
+        begin
+          user_database.set_column_type name.to_sym, (options[:new_name] || options[:name]).to_sym, options[:type]
+        rescue => e
+          message = e.message.split("\n").first
+          if message =~ /cannot be cast to type/
+            user_database.transaction do
+              random_name = "new_column_#{rand(10)*Time.now.to_i}"
+              user_database.add_column name.to_sym, random_name, options[:type]
+              user_database["UPDATE #{name} SET #{random_name}=#{(options[:new_name] || options[:name])}::#{options[:type]}"]
+              user_database.drop_column name.to_sym, (options[:new_name] || options[:name]).to_sym
+              user_database.rename_column name.to_sym, random_name, (options[:new_name] || options[:name]).to_sym
+            end
+          end
+        end
+      end
+    end
+  end
+
   def to_json(options = {})
     rows, columns, rows_count = [], [], 0
     limit      = (options[:rows_per_page] || 10).to_i

spec/acceptance/api/tables_spec.rb

@@ -152,6 +152,15 @@ feature "Tables JSON API" do
     table.reload
     table.schema.should == [[:id, "integer"], [:name, "text"], [:location, "geometry"], [:description, "text"], [:"postal code", "integer"]]
 
+    put_json "/api/json/tables/#{table.id}/update_schema", {
+                                                              :what => "modify", :column => {
+                                                                  :type => "text", :name => "postal code"
+                                                              }
+                                                           }
+    response.status.should == 200
+    table.reload
+    table.schema.should == [[:id, "integer"], [:name, "text"], [:location, "geometry"], [:description, "text"], [:"postal code", "text"]]
+
     put_json "/api/json/tables/#{table.id}/update_schema", {
                                                               :what => "add", :column => {
                                                                   :type => "integerrrr", :name => "no matter what"

spec/models/table_spec.rb

@@ -125,7 +125,19 @@ describe Table do
     }.should raise_error
     table.reload
 
-    table.add_column!(:name => "my new column", :type => "text")
+    table.add_column!(:name => "my new column", :type => "integer")
+    table.reload
+    table.schema.should == [[:id, "integer"], [:name, "text"], [:location, "geometry"], [:description, "text"], [:"my new column", "integer"]]
+
+    table.modify_column!(:old_name => "my new column", :new_name => "my new column new name", :type => "text")
+    table.reload
+    table.schema.should == [[:id, "integer"], [:name, "text"], [:location, "geometry"], [:description, "text"], [:"my new column new name", "text"]]
+
+    table.modify_column!(:old_name => "my new column new name", :new_name => "my new column")
+    table.reload
+    table.schema.should == [[:id, "integer"], [:name, "text"], [:location, "geometry"], [:description, "text"], [:"my new column", "text"]]
+
+    table.modify_column!(:name => "my new column", :type => "text")
     table.reload
     table.schema.should == [[:id, "integer"], [:name, "text"], [:location, "geometry"], [:description, "text"], [:"my new column", "text"]]
 
@@ -140,5 +152,18 @@ describe Table do
     table.schema.should == [[:id, "integer"], [:name, "text"], [:description, "text"], [:"my new column", "text"]]
   end
 
+  it "should be able to modify it's schema with castings that the DB engine doesn't support" do
+    table = create_table
+    table.schema.should == [[:id, "integer"], [:name, "text"], [:location, "geometry"], [:description, "text"]]
+
+    table.add_column!(:name => "my new column", :type => "text")
+    table.reload
+    table.schema.should == [[:id, "integer"], [:name, "text"], [:location, "geometry"], [:description, "text"], [:"my new column", "text"]]
+
+    table.modify_column!(:old_name => "my new column", :new_name => "my new column new name", :type => "integer", :force_value => "NULL")
+    table.reload
+    table.schema.should == [[:id, "integer"], [:name, "text"], [:location, "geometry"], [:description, "text"], [:"my new column new name", "integer"]]
+  end
+
 end