Sqlite preserves primary keys when copying/altering tables.

Backport #2312.
Fixes #9367.

I also added a test-case to make sure that renaming or removing
a column preserves the primary key.

4 files changed, 34 insertions, 2 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index cd105b8355..db4820b3d2 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,5 +1,11 @@
 ## unreleased ##
 
+*   Sqlite now preserves custom primary keys when copying or altering tables.
+    Fixes #9367.
+    Backport #2312.
+
+    *Sean Scally + Yves Senn*
+
 *   Preloading `has_many :through` associations with conditions won't
     cache the `:through` association. This will prevent invalid
     subsets to be cached.
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
index ca84c95bdc..455560aa55 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
@@ -490,7 +490,11 @@ module ActiveRecord
         end
 
         def copy_table(from, to, options = {}) #:nodoc:
-          options = options.merge(:id => (!columns(from).detect{|c| c.name == 'id'}.nil? && 'id' == primary_key(from).to_s))
+          from_primary_key = primary_key(from)
+          options[:primary_key] = from_primary_key if from_primary_key != 'id'
+          unless options[:primary_key]
+            options[:id] = !columns(from).detect{|c| c.name == 'id'}.nil? && 'id' == from_primary_key
+          end
           create_table(to, options) do |definition|
             @definition = definition
             columns(from).each do |column|
@@ -504,7 +508,7 @@ module ActiveRecord
                 :precision => column.precision, :scale => column.scale,
                 :null => column.null)
             end
-            @definition.primary_key(primary_key(from)) if primary_key(from)
+            @definition.primary_key(from_primary_key) if from_primary_key
             yield @definition if block_given?
           end
 
diff --git a/activerecord/test/cases/adapters/sqlite3/copy_table_test.rb b/activerecord/test/cases/adapters/sqlite3/copy_table_test.rb
index 575b4806c1..74288a98d1 100644
--- a/activerecord/test/cases/adapters/sqlite3/copy_table_test.rb
+++ b/activerecord/test/cases/adapters/sqlite3/copy_table_test.rb
@@ -57,6 +57,14 @@ class CopyTableTest < ActiveRecord::TestCase
     end
   end
 
+  def test_copy_table_with_unconventional_primary_key
+    test_copy_table('owners', 'owners_unconventional') do |from, to, options|
+      original_pk = @connection.primary_key('owners')
+      copied_pk = @connection.primary_key('owners_unconventional')
+      assert_equal original_pk, copied_pk
+    end
+  end
+
 protected
   def copy_table(from, to, options = {})
     @connection.copy_table(from, to, {:temporary => true}.merge(options))
diff --git a/activerecord/test/cases/migration_test.rb b/activerecord/test/cases/migration_test.rb
index 7bb71b7b6e..5b67d22c31 100644
--- a/activerecord/test/cases/migration_test.rb
+++ b/activerecord/test/cases/migration_test.rb
@@ -889,6 +889,20 @@ if ActiveRecord::Base.connection.supports_migrations?
       ActiveRecord::Base.connection.drop_table(:hats) rescue nil
     end
 
+    def test_removing_and_renaming_column_preserves_custom_primary_key
+      ActiveRecord::Base.connection.create_table "my_table", :primary_key => "my_table_id", :force => true do |t|
+        t.integer "col_one"
+        t.string "col_two", :limit => 128, :null => false
+      end
+
+      ActiveRecord::Base.connection.remove_column("my_table", "col_two")
+      ActiveRecord::Base.connection.rename_column("my_table", "col_one", "col_three")
+
+      assert_equal 'my_table_id', ActiveRecord::Base.connection.primary_key('my_table')
+    ensure
+      ActiveRecord::Base.connection.drop_table(:my_table) rescue nil
+    end
+
     def test_change_type_of_not_null_column
       assert_nothing_raised do
         Topic.connection.change_column "topics", "written_on", :datetime, :null => false