線上MySQL慢查詢現象案例--Impossible WHERE noticed after reading const tables
前言:2012年的筆記整理而得，發布個人博客，做備忘錄使用。 背景:線上慢查詢日志監控，得到如下的語句: 發現：select doc_text from t_wiki_doc_text where doc_title = '謝澤源'; 這條語句昨天執行特別的慢 ...
原文：Impossible WHERE noticed after reading const tables
阿里雲反饋的慢SQL，執行計划返回如下：Impossible WHERE noticed after reading const tables sql很簡單： 而且該表的request id創建了唯一索引：很明顯，這個字段是保持冪等操作的，通過數據庫的唯一索引實現 每次數據落地前，都要執行該SQL查詢是否記錄存在，而數據庫做冪等兜底 如果request id不存在，竟然沒有走request id的 ...
2019-03-21 19:31 0 1287 推薦指數：
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