diff options
| -rw-r--r-- | activerecord/CHANGELOG.md | 6 | ||||
| -rw-r--r-- | activerecord/lib/active_record/model_schema.rb | 25 | ||||
| -rw-r--r-- | activerecord/test/cases/serialized_attribute_test.rb | 28 |
3 files changed, 56 insertions, 3 deletions
diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md index 907dd894cd..d17bbf80ca 100644 --- a/activerecord/CHANGELOG.md +++ b/activerecord/CHANGELOG.md @@ -1,3 +1,9 @@ +* Loading model schema from database is now thread-safe. + + Fixes #28589. + + *Vikrant Chaudhary*, *David Abdemoulaie* + * Add `ActiveRecord::Base#cache_version` to support recyclable cache keys via the new versioned entries in `ActiveSupport::Cache`. This also means that `ActiveRecord::Base#cache_key` will now return a stable key that does not include a timestamp any more. diff --git a/activerecord/lib/active_record/model_schema.rb b/activerecord/lib/active_record/model_schema.rb index 54216caaaf..5095cdfe9f 100644 --- a/activerecord/lib/active_record/model_schema.rb +++ b/activerecord/lib/active_record/model_schema.rb @@ -1,3 +1,5 @@ +require "monitor" + module ActiveRecord module ModelSchema extend ActiveSupport::Concern @@ -152,6 +154,8 @@ module ActiveRecord self.inheritance_column = "type" delegate :type_for_attribute, to: :class + + initialize_load_schema_monitor end # Derives the join table name for +first_table+ and +second_table+. The @@ -435,15 +439,27 @@ module ActiveRecord initialize_find_by_cache end + protected + + def initialize_load_schema_monitor + @load_schema_monitor = Monitor.new + end + private + def inherited(child_class) + super + child_class.initialize_load_schema_monitor + end + def schema_loaded? - defined?(@columns_hash) && @columns_hash + defined?(@schema_loaded) && @schema_loaded end def load_schema - unless schema_loaded? - load_schema! + return if schema_loaded? + @load_schema_monitor.synchronize do + load_schema! unless defined?(@columns_hash) && @columns_hash end end @@ -457,6 +473,8 @@ module ActiveRecord user_provided_default: false ) end + + @schema_loaded = true end def reload_schema_from_cache @@ -470,6 +488,7 @@ module ActiveRecord @attributes_builder = nil @columns = nil @columns_hash = nil + @schema_loaded = false @attribute_names = nil @yaml_encoder = nil direct_descendants.each do |descendant| diff --git a/activerecord/test/cases/serialized_attribute_test.rb b/activerecord/test/cases/serialized_attribute_test.rb index 673392b4c4..e1bdaab5cf 100644 --- a/activerecord/test/cases/serialized_attribute_test.rb +++ b/activerecord/test/cases/serialized_attribute_test.rb @@ -349,4 +349,32 @@ class SerializedAttributeTest < ActiveRecord::TestCase topic.foo refute topic.changed? end + + def test_serialized_attribute_works_under_concurrent_initial_access + model = Topic.dup + + topic = model.last + topic.update group: "1" + + model.serialize :group, JSON + model.reset_column_information + + # This isn't strictly necessary for the test, but a little bit of + # knowledge of internals allows us to make failures far more likely. + model.define_singleton_method(:define_attribute) do |*args| + Thread.pass + super(*args) + end + + threads = 4.times.map do + Thread.new do + topic.reload.group + end + end + + # All the threads should retrieve the value knowing it is JSON, and + # thus decode it. If this fails, some threads will instead see the + # raw string ("1"), or raise an exception. + assert_equal [1] * threads.size, threads.map(&:value) + end end |