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.

1 files changed, 9 insertions, 8 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 29f764e8f4..0ed4e61d18 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -201,7 +201,7 @@ module ActiveRecord
       end
 
       def supports_insert_on_conflict?
-        postgresql_version >= 90500
+        database_version >= 90500
       end
       alias supports_insert_on_duplicate_skip? supports_insert_on_conflict?
       alias supports_insert_on_duplicate_update? supports_insert_on_conflict?
@@ -344,7 +344,7 @@ module ActiveRecord
       end
 
       def supports_pgcrypto_uuid?
-        postgresql_version >= 90400
+        database_version >= 90400
       end
 
       def supports_optimizer_hints?
@@ -424,7 +424,7 @@ module ActiveRecord
       }
 
       # Returns the version of the connected PostgreSQL server.
-      def postgresql_version
+      def get_database_version
         @connection.server_version
       end
 
@@ -446,12 +446,13 @@ module ActiveRecord
         sql
       end
 
-      private
-        def check_version
-          if postgresql_version < 90300
-            raise "Your version of PostgreSQL (#{postgresql_version}) is too old. Active Record supports PostgreSQL >= 9.3."
-          end
+      def check_version # :nodoc:
+        if database_version < 90300
+          raise "Your version of PostgreSQL (#{database_version}) is too old. Active Record supports PostgreSQL >= 9.3."
         end
+      end
+
+      private
 
         # See https://www.postgresql.org/docs/current/static/errcodes-appendix.html
         VALUE_LIMIT_VIOLATION = "22001"