Cache database version in schema cache

  * The database version will get cached in the schema cache file during the
    schema cache dump. When the database version check happens, the version will
    be pulled from the schema cache and thus avoid querying the database for
    the version.
  * If the schema cache file doesn't exist, we'll query the database for the
    version and cache it on the schema cache object.
  * To facilitate this change, all connection adapters now implement
    #get_database_version and #database_version. #database_version returns the
    value from the schema cache.
  * To take advantage of the cached database version, the database version check
    will now happen after the schema cache is set on the connection in the
    connection pool.

2 files changed, 1 insertions, 4 deletions

diff --git a/activerecord/test/cases/adapters/mysql2/datetime_precision_quoting_test.rb b/activerecord/test/cases/adapters/mysql2/datetime_precision_quoting_test.rb
index 00a075e063..cbe55f1d53 100644
--- a/activerecord/test/cases/adapters/mysql2/datetime_precision_quoting_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/datetime_precision_quoting_test.rb
@@ -46,10 +46,7 @@ class Mysql2DatetimePrecisionQuotingTest < ActiveRecord::Mysql2TestCase
 
     def stub_version(full_version_string)
       @connection.stub(:full_version, full_version_string) do
-        @connection.remove_instance_variable(:@version) if @connection.instance_variable_defined?(:@version)
         yield
       end
-    ensure
-      @connection.remove_instance_variable(:@version) if @connection.instance_variable_defined?(:@version)
     end
 end
diff --git a/activerecord/test/cases/adapters/mysql2/sp_test.rb b/activerecord/test/cases/adapters/mysql2/sp_test.rb
index 7b6dce71e9..626ef59570 100644
--- a/activerecord/test/cases/adapters/mysql2/sp_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/sp_test.rb
@@ -9,7 +9,7 @@ class Mysql2StoredProcedureTest < ActiveRecord::Mysql2TestCase
 
   def setup
     @connection = ActiveRecord::Base.connection
-    unless ActiveRecord::Base.connection.version >= "5.6.0"
+    unless ActiveRecord::Base.connection.database_version >= "5.6.0"
       skip("no stored procedure support")
     end
   end