Added migration support for SQLite (using temporary tables to simulate ALTER TABLE) #1771 [Sam Stephenson]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@1893 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

4 files changed, 209 insertions, 17 deletions

diff --git a/activerecord/CHANGELOG b/activerecord/CHANGELOG
index 07fd379b88..3bf9ba5fcf 100644
--- a/activerecord/CHANGELOG
+++ b/activerecord/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Added migration support for SQLite (using temporary tables to simulate ALTER TABLE) #1771 [Sam Stephenson]
+
 * Remove extra definition of supports_migrations? from abstract_adaptor.rb [Nicholas Seckar]
 
 * Fix acts_as_list so that moving next-to-last item to the bottom does not result in duplicate item positions
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index e9473c1ca5..ff34c63fa1 100755
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -380,10 +380,11 @@ module ActiveRecord
         table_definition.primary_key(options[:primary_key] || "id") unless options[:id] == false
 
         yield table_definition
-        create_sql = "CREATE TABLE #{name} ("
+        create_sql = "CREATE#{' TEMPORARY' if options[:temporary]} TABLE "
+        create_sql << "#{name} ("
         create_sql << table_definition.to_sql
         create_sql << ") #{options[:options]}"
-                
+
         execute create_sql
       end
 
@@ -494,6 +495,20 @@ module ActiveRecord
         end
     end
 
+    class ColumnDefinition < Struct.new(:base, :name, :type, :limit, :default)
+      def to_sql
+        column_sql = "#{name} #{type_to_sql(type.to_sym, limit)}"
+        column_sql << " DEFAULT '#{default}'" if default
+        column_sql
+      end
+      alias to_s :to_sql
+      
+    private
+      def type_to_sql(name, limit)
+        base.type_to_sql(name, limit) rescue name
+      end   
+    end
+
     class TableDefinition
       attr_accessor :columns
 
@@ -503,29 +518,28 @@ module ActiveRecord
       end
 
       def primary_key(name)
-        @columns << "#{name} #{native[:primary_key]}"
+        return unless column = self[name]
+        column.type = native[:primary_key]
         self
       end
+      
+      def [](name)
+        @columns.find {|column| column.name == name}
+      end
 
       def column(name, type, options = {})
-        limit = options[:limit] || native[type.to_sym][:limit]
-        
-        column_sql = "#{name} #{type_to_sql(type.to_sym, options[:limit])}"
-        column_sql << " DEFAULT '#{options[:default]}'" if options[:default]
-        @columns << column_sql
+        column = self[name] || ColumnDefinition.new(@base, name, type)
+        column.limit = options[:limit] || native[type.to_sym][:limit]
+        column.default = options[:default]
+        @columns << column unless @columns.include? column
         self
       end
-      
+            
       def to_sql
-        @columns.join(", ")
-      end
-      
-      private
-      
-      def type_to_sql(name, limit)
-        @base.type_to_sql(name, limit)
+        @columns * ', '
       end
       
+    private
       def native
         @base.native_database_types
       end
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
index fbf4aa398f..212e11de4e 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
@@ -103,6 +103,10 @@ module ActiveRecord
         }
       end
 
+      def supports_migrations?
+        true
+      end
+
       def execute(sql, name = nil)
         #log(sql, name, @connection) { |connection| connection.execute(sql) }
         log(sql, name) { @connection.execute(sql) }
@@ -157,6 +161,11 @@ module ActiveRecord
         }
       end
 
+      def primary_key(table_name)
+        column = table_structure(table_name).find {|field| field['pk'].to_i == 1}
+        column ? column['name'] : nil
+      end
+
       def quote_string(s)
         @connection.class.quote(s)
       end
@@ -169,10 +178,113 @@ module ActiveRecord
         'SQLite'
       end
 
+      def remove_index(table_name, column_name)
+        execute "DROP INDEX #{table_name}_#{column_name}_index"
+      end
+
+      def add_column(table_name, column_name, type, options = {})
+        alter_table(table_name) do |definition|
+          definition.column(column_name, type, options)
+        end
+      end
+      
+      def remove_column(table_name, column_name)
+        alter_table(table_name) do |definition|
+          definition.columns.delete(definition[column_name])
+        end
+      end
+      
+      def change_column_default(table_name, column_name, default)
+        alter_table(table_name) do |definition|
+          definition[column_name].default = default
+        end
+      end
+
+      def change_column(table_name, column_name, type, options = {})
+        alter_table(table_name) do |definition|
+          definition[column_name].instance_eval do
+            self.type    = type
+            self.limit   = options[:limit] if options[:limit]
+            self.default = options[:default] if options[:default]
+          end
+        end
+      end
+
+      def rename_column(table_name, column_name, new_column_name)
+        alter_table(table_name, :rename => {column_name => new_column_name})
+      end
+          
 
       protected
         def table_structure(table_name)
-          execute "PRAGMA table_info(#{table_name})"
+          returning structure = execute("PRAGMA table_info(#{table_name})") do
+            raise ActiveRecord::StatementInvalid if structure.empty?
+          end
+        end
+        
+        def indexes(table_name)
+          execute("PRAGMA index_list(#{table_name})").map do |index|
+            index_info = execute("PRAGMA index_info(#{index['name']})")
+            {
+              :name    => index['name'],
+              :unique  => index['unique'].to_i == 1,
+              :columns => index_info.map {|info| info['name']}
+            }
+          end
+        end
+        
+        def alter_table(table_name, options = {}) #:nodoc:
+          altered_table_name = "altered_#{table_name}"
+          caller = lambda {|definition| yield definition if block_given?}
+
+          transaction do
+            move_table(table_name, altered_table_name, 
+              options.merge(:temporary => true), &caller)
+            move_table(altered_table_name, table_name, &caller)
+          end
+        end
+        
+        def move_table(from, to, options = {}, &block) #:nodoc:
+          copy_table(from, to, options, &block)
+          drop_table(from)
+        end
+        
+        def copy_table(from, to, options = {}) #:nodoc:
+          create_table(to, options) do |@definition|
+            columns(from).each do |column|
+              column_name = options[:rename][column.name] if 
+                options[:rename][column.name] if options[:rename]
+              
+              @definition.column(column_name || column.name, column.type, 
+                :limit => column.limit, :default => column.default)
+            end
+            @definition.primary_key(primary_key(from))
+            yield @definition if block_given?
+          end
+          
+          copy_table_indexes(from, to)
+          copy_table_contents(from, to, 
+            @definition.columns.map {|column| column.name}, 
+            options[:rename] || {})
+        end
+        
+        def copy_table_indexes(from, to) #:nodoc:
+          indexes(from).each do |index|
+            type = index[:unique] ? 'UNIQUE' : ''
+            add_index(to, index[:columns], type)
+          end
+        end
+        
+        def copy_table_contents(from, to, columns, rename = {}) #:nodoc:
+          column_mappings = Hash[*columns.map {|name| [name, name]}.flatten]
+          rename.inject(column_mappings) {|map, a| map[a.last] = a.first; map}
+          
+          @connection.execute "SELECT * FROM #{from}" do |row|
+            sql = "INSERT INTO #{to} VALUES ("
+            sql << columns.map {|col| quote row[column_mappings[col]]} * ', '
+            sql << ')'
+            @connection.execute sql
+          end
         end
     end
 
diff --git a/activerecord/test/copy_table_sqlite.rb b/activerecord/test/copy_table_sqlite.rb
new file mode 100644
index 0000000000..f3f5f1ce46
--- /dev/null
+++ b/activerecord/test/copy_table_sqlite.rb
@@ -0,0 +1,64 @@
+require 'abstract_unit'
+
+class CopyTableTest < Test::Unit::TestCase
+  fixtures :companies, :comments
+  
+  def setup
+    @connection = ActiveRecord::Base.connection
+    class << @connection
+      public :copy_table, :table_structure, :indexes
+    end
+  end
+  
+  def test_copy_table(from = 'companies', to = 'companies2', options = {})
+    assert_nothing_raised {copy_table(from, to, options)}
+    assert_equal row_count(from), row_count(to)
+      
+    if block_given?
+      yield from, to, options
+    else
+      assert_equal column_names(from), column_names(to)
+    end
+    
+    @connection.drop_table(to) rescue nil
+  end
+  
+  def test_copy_table_renaming_column
+    test_copy_table('companies', 'companies2', 
+        :rename => {'client_of' => 'fan_of'}) do |from, to, options|
+      assert_equal column_values(from, 'client_of').compact.sort, 
+                   column_values(to, 'fan_of').compact.sort
+    end
+  end
+  
+  def test_copy_table_with_index
+    test_copy_table('comments', 'comments_with_index') do
+      @connection.add_index('comments_with_index', ['post_id', 'type'])
+      test_copy_table('comments_with_index', 'comments_with_index2') do
+        assert_equal table_indexes_without_name('comments_with_index'),
+                     table_indexes_without_name('comments_with_index2')
+      end
+    end
+  end
+  
+protected
+  def copy_table(from, to, options = {})
+    @connection.copy_table(from, to, {:temporary => true}.merge(options))
+  end
+
+  def column_names(table)
+    @connection.table_structure(table).map {|column| column['name']}
+  end
+  
+  def column_values(table, column)
+    @connection.select_all("SELECT #{column} FROM #{table}").map {|row| row[column]}
+  end
+
+  def table_indexes_without_name(table)
+    @connection.indexes('comments_with_index').delete(:name)
+  end
+  
+  def row_count(table)
+    @connection.select_one("SELECT COUNT(*) AS count FROM #{table}")['count']
+  end
+end