-- Per-user delete (hide). Does not change t_messages.status or the peer's history.

CREATE TABLE IF NOT EXISTS t_message_deletes (
    user_id           BIGINT NOT NULL COMMENT '删除者 user_id，仅该用户历史不可见',
    msg_id            BIGINT NOT NULL COMMENT '被删除的 Snowflake MsgId',
    conversation_id   BIGINT NOT NULL COMMENT '所属会话，便于按会话过滤',
    created_at        DATETIME(3) NOT NULL COMMENT '删除时间',
    PRIMARY KEY (user_id, msg_id),
    KEY idx_user_conv_msg (user_id, conversation_id, msg_id)
) COMMENT='用户删除消息（只对自己隐藏）。对端仍可见；全员撤回走 t_messages.status=2';