Issue #3264471 by mcdruid, poker10:...

      ->execute();

    // Ensure that expressions are handled properly. This should set every

    // record's age to a square of itself, which will change only three of the

    // four records in the table since 1*1 = 1. That means only three records

    // are modified, so we should get back 3, not 4, from execute().

    // record's age to a square of itself. The number of affected rows returned

    // by db_update() will vary across different database engines and versions:

    // - MySQL / InnoDB: changed rows only

    // - MySQL / MyISAM: changed rows only

    // - PostgreSQL: all rows matched by the query

    // - SQLite: changed rows only (see workaround in UpdateQuery_sqlite)

    // All database engines will change only three of the four records in the

    // table since 1*1 = 1. However, the pgsql driver will return the number of

    // rows matched rather than the number changed.

    // @see https://www.drupal.org/project/drupal/issues/805858

    // @see https://www.drupal.org/project/drupal/issues/3264471

    $connection = Database::getConnection()->getConnectionOptions();

    $expected_rows = 3;

    if ($connection['driver'] === 'pgsql') {

      $expected_rows ++;

    }

    $num_rows = db_update('test')

      ->expression('age', 'age * age')

      ->execute();

    $this->assertIdentical($num_rows, 3, 'Number of affected rows are returned.');

    $this->assertIdentical($num_rows, $expected_rows, 'Number of affected rows are returned.');

    $saved_name = db_query('SELECT name FROM {test} WHERE age = :age', array(':age' => pow(26, 2)))->fetchField();

    $this->assertIdentical('Paul', $saved_name, 'Successfully updated values using an algebraic expression.');

  }

}