[
  {
    "type": "alter_table",
    "description": "Add composite index for efficient unread count queries",
    "database": "{{store}}",
    "check_query": "SELECT INDEX_NAME FROM INFORMATION_SCHEMA.STATISTICS WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 'chat_messages' AND INDEX_NAME = 'idx_thread_direction_created'",
    "sql": "ALTER TABLE `chat_messages` ADD INDEX `idx_thread_direction_created` (`thread_id`, `direction`, `created_at`)"
  }
]