Merge pull request #36371 from eileencodes/move-schema-cache-to-pool

Move schema cache to pool

activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb

@@ -20,6 +20,26 @@ class ExclusiveConnectionTimeoutError < ConnectionTimeoutError
   end
 
   module ConnectionAdapters
+    module AbstractPool # :nodoc:
+      def get_schema_cache(connection)
+        @schema_cache ||= SchemaCache.new(connection)
+        @schema_cache.connection = connection
+        @schema_cache
+      end
+
+      def set_schema_cache(cache)
+        @schema_cache = cache
+      end
+    end
+
+    class NullPool # :nodoc:
+      include ConnectionAdapters::AbstractPool
+
+      def initialize
+        @schema_cache = nil
+      end
+    end
+
     # Connection pool base class for managing Active Record database
     # connections.
     #
@@ -336,6 +356,7 @@ def run
 
       include MonitorMixin
       include QueryCache::ConnectionPoolConfiguration
+      include ConnectionAdapters::AbstractPool
 
       attr_accessor :automatic_reconnect, :checkout_timeout, :schema_cache
       attr_reader :spec, :connections, :size, :reaper
@@ -837,7 +858,6 @@ def remove_connection_from_thread_cache(conn, owner_thread = conn.owner)
 
         def new_connection
           Base.send(spec.adapter_method, spec.config).tap do |conn|
-            conn.schema_cache = schema_cache.dup if schema_cache
             conn.check_version
           end
         end

activerecord/lib/active_record/connection_adapters/abstract_adapter.rb

@@ -78,7 +78,7 @@ class AbstractAdapter
       SIMPLE_INT = /\A\d+\z/
 
       attr_accessor :pool
-      attr_reader :schema_cache, :visitor, :owner, :logger, :lock, :prepared_statements, :prevent_writes
+      attr_reader :visitor, :owner, :logger, :lock, :prepared_statements, :prevent_writes
       alias :in_use? :owner
 
       set_callback :checkin, :after, :enable_lazy_transactions!
@@ -114,9 +114,8 @@ def initialize(connection, logger = nil, config = {}) # :nodoc:
         @instrumenter        = ActiveSupport::Notifications.instrumenter
         @logger              = logger
         @config              = config
-        @pool                = nil
+        @pool                = ActiveRecord::ConnectionAdapters::NullPool.new
         @idle_since          = Concurrent.monotonic_time
-        @schema_cache        = SchemaCache.new self
         @quoted_column_names, @quoted_table_names = {}, {}
         @prevent_writes = false
         @visitor = arel_visitor
@@ -206,9 +205,13 @@ def lease
         @owner = Thread.current
       end
 
+      def schema_cache
+        @pool.get_schema_cache(self)
+      end
+
       def schema_cache=(cache)
         cache.connection = self
-        @schema_cache = cache
+        @pool.set_schema_cache(cache)
       end
 
       # this method must only be called while holding connection pool's mutex
@@ -487,6 +490,9 @@ def discard!
         #
         # Prevent @connection's finalizer from touching the socket, or
         # otherwise communicating with its server, when it is collected.
+        if schema_cache.connection == self
+          schema_cache.connection = nil
+        end
       end
 
       # Reset the state of this connection, directing the DBMS to clear

activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb

@@ -109,6 +109,7 @@ def disconnect!
       end
 
       def discard! # :nodoc:
+        super
         @connection.automatic_close = false
         @connection = nil
       end

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -302,6 +302,7 @@ def disconnect!
       end
 
       def discard! # :nodoc:
+        super
         @connection.socket_io.reopen(IO::NULL) rescue nil
         @connection = nil
       end

activerecord/lib/active_record/railtie.rb

@@ -134,7 +134,6 @@ class Railtie < Rails::Railtie # :nodoc:
 
               cache = YAML.load(File.read(filename))
               if cache.version == current_version
-                connection.schema_cache = cache
                 connection_pool.schema_cache = cache.dup
               else
                 warn "Ignoring db/schema_cache.yml because it has expired. The current schema version is #{current_version}, but the one in the cache is #{cache.version}."

activerecord/test/cases/connection_pool_test.rb

@@ -507,7 +507,6 @@ def test_pool_sets_connection_schema_cache
         pool.schema_cache = schema_cache
 
         pool.with_connection do |conn|
-          assert_not_same pool.schema_cache, conn.schema_cache
           assert_equal pool.schema_cache.size, conn.schema_cache.size
           assert_same pool.schema_cache.columns(:posts), conn.schema_cache.columns(:posts)
         end