Merge pull request #49349 from fractaledmind/ar-sqlite-tune-connectio…

…n-config

Performance tune the SQLite3 adapter connection configuration

activerecord/CHANGELOG.md

@@ -1,3 +1,9 @@
+*   Performance tune the SQLite3 adapter connection configuration
+
+    For Rails applications, the Write-Ahead-Log in normal syncing mode with a capped journal size, a healthy shared memory buffer and a shared cache will perform, on average, 2× better.
+
+    *Stephen Margheim*
+
 *   Allow SQLite3 `busy_handler` to be configured with simple max number of `retries`
 
     Retrying busy connections without delay is a preferred practice for performance-sensitive applications. Add support for a `database.yml` `retries` integer, which is used in a simple `busy_handler` function to retry busy connections without exponential backoff up to the max number of `retries`.

activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb

@@ -723,7 +723,29 @@ def configure_connection
             end
           end
 
+          # Enforce foreign key constraints
+          # https://www.sqlite.org/pragma.html#pragma_foreign_keys
+          # https://www.sqlite.org/foreignkeys.html
           raw_execute("PRAGMA foreign_keys = ON", "SCHEMA")
+          unless @memory_database
+            # Journal mode WAL allows for greater concurrency (many readers + one writer)
+            # https://www.sqlite.org/pragma.html#pragma_journal_mode
+            raw_execute("PRAGMA journal_mode = WAL", "SCHEMA")
+            # Set more relaxed level of database durability
+            # 2 = "FULL" (sync on every write), 1 = "NORMAL" (sync every 1000 written pages) and 0 = "NONE"
+            # https://www.sqlite.org/pragma.html#pragma_synchronous
+            raw_execute("PRAGMA synchronous = NORMAL", "SCHEMA")
+            # Set the global memory map so all processes can share some data
+            # https://www.sqlite.org/pragma.html#pragma_mmap_size
+            # https://www.sqlite.org/mmap.html
+            raw_execute("PRAGMA mmap_size = #{128.megabytes}", "SCHEMA")
+          end
+          # Impose a limit on the WAL file to prevent unlimited growth
+          # https://www.sqlite.org/pragma.html#pragma_journal_size_limit
+          raw_execute("PRAGMA journal_size_limit = #{64.megabytes}", "SCHEMA")
+          # Set the local connection cache to 2000 pages
+          # https://www.sqlite.org/pragma.html#pragma_cache_size
+          raw_execute("PRAGMA cache_size = 2000", "SCHEMA")
         end
     end
     ActiveSupport.run_load_hooks(:active_record_sqlite3adapter, SQLite3Adapter)

activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb

@@ -136,6 +136,26 @@ def test_encoding
         assert_equal "UTF-8", @conn.encoding
       end
 
+      def test_default_pragmas
+        if in_memory_db?
+          assert_equal [{ "foreign_keys" => 1 }], @conn.execute("PRAGMA foreign_keys")
+          assert_equal [{ "journal_mode" => "memory" }], @conn.execute("PRAGMA journal_mode")
+          assert_equal [{ "synchronous" => 2 }], @conn.execute("PRAGMA synchronous")
+          assert_equal [{ "journal_size_limit" => 67108864 }], @conn.execute("PRAGMA journal_size_limit")
+          assert_equal [], @conn.execute("PRAGMA mmap_size")
+          assert_equal [{ "cache_size" => 2000 }], @conn.execute("PRAGMA cache_size")
+        else
+          with_file_connection do |conn|
+            assert_equal [{ "foreign_keys" => 1 }], conn.execute("PRAGMA foreign_keys")
+            assert_equal [{ "journal_mode" => "wal" }], conn.execute("PRAGMA journal_mode")
+            assert_equal [{ "synchronous" => 1 }], conn.execute("PRAGMA synchronous")
+            assert_equal [{ "journal_size_limit" => 67108864 }], conn.execute("PRAGMA journal_size_limit")
+            assert_equal [{ "mmap_size" => 134217728 }], conn.execute("PRAGMA mmap_size")
+            assert_equal [{ "cache_size" => 2000 }], conn.execute("PRAGMA cache_size")
+          end
+        end
+      end
+
       def test_exec_no_binds
         with_example_table "id int, data string" do
           result = @conn.exec_query("SELECT id, data FROM ex")
@@ -815,6 +835,17 @@ def with_strict_strings_by_default
         ensure
           SQLite3Adapter.strict_strings_by_default = false
         end
+
+        def with_file_connection(options = {})
+          options = options.dup
+          db_config = ActiveRecord::Base.configurations.configurations.find { |config| !config.database.include?(":memory:") }
+          options[:database] ||= db_config.database
+          conn = ActiveRecord::Base.sqlite3_connection(options)
+
+          yield(conn)
+        ensure
+          conn.disconnect! if conn
+        end
     end
   end
 end