Schema Cache: cache table indexes

Useful to not query for indexes when an application uses schema cache.

Ref #35546

activerecord/lib/active_record/connection_adapters/schema_cache.rb

@@ -13,6 +13,7 @@ def initialize(conn)
         @columns_hash = {}
         @primary_keys = {}
         @data_sources = {}
+        @indexes      = {}
       end
 
       def initialize_dup(other)
@@ -21,22 +22,25 @@ def initialize_dup(other)
         @columns_hash = @columns_hash.dup
         @primary_keys = @primary_keys.dup
         @data_sources = @data_sources.dup
+        @indexes      = @indexes.dup
       end
 
       def encode_with(coder)
-        coder["columns"] = @columns
+        coder["columns"]      = @columns
         coder["columns_hash"] = @columns_hash
         coder["primary_keys"] = @primary_keys
         coder["data_sources"] = @data_sources
-        coder["version"] = connection.migration_context.current_version
+        coder["indexes"]      = @indexes
+        coder["version"]      = connection.migration_context.current_version
       end
 
       def init_with(coder)
-        @columns = coder["columns"]
+        @columns      = coder["columns"]
         @columns_hash = coder["columns_hash"]
         @primary_keys = coder["primary_keys"]
         @data_sources = coder["data_sources"]
-        @version = coder["version"]
+        @indexes      = coder["indexes"]
+        @version      = coder["version"]
       end
 
       def primary_keys(table_name)
@@ -57,6 +61,7 @@ def add(table_name)
           primary_keys(table_name)
           columns(table_name)
           columns_hash(table_name)
+          indexes(table_name)
         end
       end
 
@@ -82,17 +87,22 @@ def columns_hash?(table_name)
         @columns_hash.key?(table_name)
       end
 
+      def indexes(table_name)
+        @indexes[table_name] ||= connection.indexes(table_name)
+      end
+
       # Clears out internal caches
       def clear!
         @columns.clear
         @columns_hash.clear
         @primary_keys.clear
         @data_sources.clear
+        @indexes.clear
         @version = nil
       end
 
       def size
-        [@columns, @columns_hash, @primary_keys, @data_sources].map(&:size).inject :+
+        [@columns, @columns_hash, @primary_keys, @data_sources, @indexes].map(&:size).inject :+
       end
 
       # Clear out internal caches for the data source +name+.
@@ -101,20 +111,20 @@ def clear_data_source_cache!(name)
         @columns_hash.delete name
         @primary_keys.delete name
         @data_sources.delete name
+        @indexes.delete name
       end
 
       def marshal_dump
         # if we get current version during initialization, it happens stack over flow.
         @version = connection.migration_context.current_version
-        [@version, @columns, @columns_hash, @primary_keys, @data_sources]
+        [@version, @columns, @columns_hash, @primary_keys, @data_sources, @indexes]
       end
 
       def marshal_load(array)
-        @version, @columns, @columns_hash, @primary_keys, @data_sources = array
+        @version, @columns, @columns_hash, @primary_keys, @data_sources, @indexes = array
       end
 
       private
-
         def prepare_data_sources
           connection.data_sources.each { |source| @data_sources[source] = true }
         end

activerecord/test/cases/connection_adapters/schema_cache_test.rb

@@ -19,13 +19,15 @@ def test_yaml_dump_and_load
         @cache.columns_hash("posts")
         @cache.data_sources("posts")
         @cache.primary_keys("posts")
+        @cache.indexes("posts")
 
         new_cache = YAML.load(YAML.dump(@cache))
         assert_no_queries do
           assert_equal 12, new_cache.columns("posts").size
           assert_equal 12, new_cache.columns_hash("posts").size
           assert new_cache.data_sources("posts")
           assert_equal "id", new_cache.primary_keys("posts")
+          assert_equal 1, new_cache.indexes("posts").size
         end
       end
 
@@ -39,6 +41,10 @@ def test_yaml_loads_5_1_dump
           assert cache.data_sources("posts")
           assert_equal "id", cache.primary_keys("posts")
         end
+
+        assert_queries 1 do
+          assert_equal 1, cache.indexes("posts")
+        end
       end
 
       def test_primary_key_for_non_existent_table
@@ -55,11 +61,17 @@ def test_caches_columns_hash
         assert_equal columns_hash, @cache.columns_hash("posts")
       end
 
+      def test_caches_indexes
+        indexes = @cache.indexes("posts")
+        assert_equal indexes, @cache.indexes("posts")
+      end
+
       def test_clearing
         @cache.columns("posts")
         @cache.columns_hash("posts")
         @cache.data_sources("posts")
         @cache.primary_keys("posts")
+        @cache.indexes("posts")
 
         @cache.clear!
 
@@ -71,6 +83,7 @@ def test_dump_and_load
         @cache.columns_hash("posts")
         @cache.data_sources("posts")
         @cache.primary_keys("posts")
+        @cache.indexes("posts")
 
         @cache = Marshal.load(Marshal.dump(@cache))
 
@@ -79,6 +92,7 @@ def test_dump_and_load
           assert_equal 12, @cache.columns_hash("posts").size
           assert @cache.data_sources("posts")
           assert_equal "id", @cache.primary_keys("posts")
+          assert_equal 1, @cache.indexes("posts").size
         end
       end
 
@@ -108,7 +122,6 @@ def test_clear_data_source_cache
       end
 
       private
-
         def schema_dump_path
           "test/assets/schema_dump_5_1.yml"
         end