使用udi计数器跟踪数据变化。
迁移用包装的方式组合了协调模式变化和数据变化的威力和简单性。
Migrations combine power and simplicity to coordinate both schema changes and data changes using a wrapping approach.
事实上,正确的思路应该是:执行查找的频率与数据变化的频率有关。
In fact, the line of reasoning should simply be how frequently your data changes with respect to how frequently you perform your lookups.
They live much longer lives and they live to die of something else and the leading causes of death currently haven't changed very much since 1997 when this data was published: they die of heart disease and cancer primarily.
人们活的更久了,不过会死于另一些疾病,如今导致死亡的主要原因,并没有太大的变化,自一九九七年有相关数据公开开始,其显示人们主要死于心脏病和癌症
You could take weights on people measured over a period of many years and look at the variability over time in weight and then link it to things like heart disease and cancer, and I'll come back later and talk about the results of that particular study.
我们还可以得到人们很长一段时间里,每年的体重数据,观察体重随着时间变化的变动,并将观察结果与心脏疾病和癌症联系起来,我等一下会告诉大家这项研究的结果
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