是否有可能找出“优化”命令能够对给定表格进行碎片整理多less？ 我只是想事先了解这些信息。
我对这个答案有了一些第二个想法:-)其实就像查找价值一样简单 – 其全部在information_schema.tables中！ 查找名为data_free的字段，它具有正确的值，并且在我所做的示例中也行得通：
use test; create table test1 as select * from information_schema.tables; alter table test1 engine = myisam; -- not even necessary select * from information_schema.tables where table_name = 'test1'\G delete from test1 limit 10; select * from information_schema.tables where table_name = 'test1'\G analyze table test1; select * from information_schema.tables where table_name = 'test1'\G optimize table test1; select * from information_schema.tables where table_name = 'test1'\G information_schema.tables始终显示正确的数据长度，因此您可以将data_length字段与所需数据长度（avg_row_length * table_rows）的粗略估计进行比较，但是只有使用分析表更新了统计信息后：
analyze table 'TABLE_TO_LOOK_UP'; -- to get row count etc. right SELECT table_name, concat( round((data_length - (avg_row_length * table_rows)) / 1024 / 1024, 2) , 'M' ) very_theoretical_size_difference_in_MB FROM information_schema.tables WHERE table_name = 'TABLE_TO_LOOK_UP';