Improve detection of ActiveRecord::StatementTimeout with mysql2 adapter

in the edge case when the query is terminated by MySQL server during filesort.
See https://bugs.mysql.com/bug.php?id=96537 for more details.

activerecord/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Improve detection of ActiveRecord::StatementTimeout with mysql2 adapter in the edge case when the query is terminated during filesort.
+
+    *Kir Shatrov*
+
 *   Stop trying to read yaml file fixtures when loading Active Record fixtures.
 
     *Gannon McGibbon*

activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb

@@ -574,6 +574,7 @@ def extract_precision(sql_type)
 
         # See https://dev.mysql.com/doc/refman/5.7/en/server-error-reference.html
         ER_DB_CREATE_EXISTS     = 1007
+        ER_FILSORT_ABORT        = 1028
         ER_DUP_ENTRY            = 1062
         ER_NOT_NULL_VIOLATION   = 1048
         ER_NO_REFERENCED_ROW    = 1216
@@ -617,7 +618,7 @@ def translate_exception(exception, message:, sql:, binds:)
             Deadlocked.new(message, sql: sql, binds: binds)
           when ER_LOCK_WAIT_TIMEOUT
             LockWaitTimeout.new(message, sql: sql, binds: binds)
-          when ER_QUERY_TIMEOUT
+          when ER_QUERY_TIMEOUT, ER_FILSORT_ABORT
             StatementTimeout.new(message, sql: sql, binds: binds)
           when ER_QUERY_INTERRUPTED
             QueryCanceled.new(message, sql: sql, binds: binds)

activerecord/test/cases/adapters/mysql2/mysql2_adapter_test.rb

@@ -240,6 +240,21 @@ def test_read_timeout_exception
     ActiveRecord::Base.establish_connection :arunit
   end
 
+  def test_statement_timeout_error_codes
+    raw_conn = @conn.raw_connection
+    assert_raises(ActiveRecord::StatementTimeout) do
+      raw_conn.stub(:query, ->(_sql) { raise Mysql2::Error.new("fail", 50700, ActiveRecord::ConnectionAdapters::AbstractMysqlAdapter::ER_FILSORT_ABORT) }) {
+        @conn.execute("SELECT 1")
+      }
+    end
+
+    assert_raises(ActiveRecord::StatementTimeout) do
+      raw_conn.stub(:query, ->(_sql) { raise Mysql2::Error.new("fail", 50700, ActiveRecord::ConnectionAdapters::AbstractMysqlAdapter::ER_QUERY_TIMEOUT) }) {
+        @conn.execute("SELECT 1")
+      }
+    end
+  end
+
   private
     def with_example_table(definition = "id int auto_increment primary key, number int, data varchar(255)", &block)
       super(@conn, "ex", definition, &block)