Fix GH #4674. Reset column information and sequence name when setting table_name.

2 files changed, 24 insertions, 4 deletions

diff --git a/activerecord/lib/active_record/model_schema.rb b/activerecord/lib/active_record/model_schema.rb
index 60bac2f802..8710884bfd 100644
--- a/activerecord/lib/active_record/model_schema.rb
+++ b/activerecord/lib/active_record/model_schema.rb
@@ -114,10 +114,17 @@ module ActiveRecord
       # You can also just define your own <tt>self.table_name</tt> method; see
       # the documentation for ActiveRecord::Base#table_name.
       def table_name=(value)
-        @table_name        = value && value.to_s
-        @quoted_table_name = nil
-        @arel_table        = nil
-        @relation          = Relation.new(self, arel_table)
+        value = value && value.to_s
+        if defined?(@table_name)
+          return if value == @table_name
+
+          reset_column_information
+        end
+        @table_name          = value
+        @quoted_table_name   = nil
+        @arel_table          = nil
+        @sequence_name       = nil
+        @relation            = Relation.new(self, arel_table)
       end
 
       # Returns a quoted version of the table name, used to construct SQL statements.
diff --git a/activerecord/test/cases/base_test.rb b/activerecord/test/cases/base_test.rb
index 698c3d0cb1..d810704418 100644
--- a/activerecord/test/cases/base_test.rb
+++ b/activerecord/test/cases/base_test.rb
@@ -1479,6 +1479,19 @@ class BasicsTest < ActiveRecord::TestCase
     end
   end
 
+  def test_clear_cash_when_setting_table_name
+    Joke.table_name = "cold_jokes"
+    before_columns = Joke.columns
+    before_seq     = Joke.sequence_name
+
+    Joke.table_name = "funny_jokes"
+    after_columns = Joke.columns
+    after_seq     = Joke.sequence_name
+
+    assert_not_equal before_columns, after_columns
+    assert_not_equal before_seq, after_seq unless before_seq.blank? && after_seq.blank?
+  end
+
   def test_set_table_name_symbol_converted_to_string
     Joke.table_name = :cold_jokes
     assert_equal 'cold_jokes', Joke.table_name