{
  "id": "m0021",
  "title": "llm_usage 删除 req_tokens/resp_tokens 冗余列（2026-09-10 用户定夺：usages JSON 是计费唯一事实源，token 计数在其中；两列与 usages 同源冗余且曾被截断病根牵连，统计查询改 JSON_EXTRACT）。dmig 幂等守卫：列已不存在自动跳过",
  "backup_tables": ["llm_usage"],
  "up": [
    {"op": "sql", "sql": "ALTER TABLE llm_usage DROP COLUMN req_tokens"},
    {"op": "sql", "sql": "ALTER TABLE llm_usage DROP COLUMN resp_tokens"}
  ],
  "down": [
    {"op": "sql", "sql": "ALTER TABLE llm_usage ADD COLUMN req_tokens INT NOT NULL DEFAULT 0 COMMENT '请求token(历史冗余列,计费看usages)'"},
    {"op": "sql", "sql": "ALTER TABLE llm_usage ADD COLUMN resp_tokens INT NOT NULL DEFAULT 0 COMMENT '响应token(历史冗余列,计费看usages)'"}
  ]
}