为什么我的 MySQL 索引基数被清零？
我有一个使用 MySQL 数据库 (MYISAM) 的旧 Web 应用程序。我最近注意到应用程序的性能急剧下降。检查我的索引后，我注意到所有索引的基数都报告为零。
我可以通过对每个表执行 ANALYZE TABLE 来解决此问题。
但我很好奇，是什么导致基数首先被清零？
I have an older web application that uses a MySQL Database (MYISAM). I noticed recently that the performance of the application was drastically reduced. After checking on my indexes, I noticed that the cardinality for all of them was reporting zero.
I was able to fix this by doing an ANALYZE TABLE on each table.
But I'm curious, what causes the cardinality to get zeroed out in the first place?
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从内存中，某些修复表操作会擦除统计信息，您需要分析表才能恢复它们。
除此之外，我想不出任何应该将它们归零的原因。我只是希望它们会过时。
From memory, some repair table operations wipe the statistics and you need to ANALYZE TABLE to get them back.
Other than that, I can't think of any reason why they should be zeroed. I'd just expect that they'd be out of date.