我该如何处理>使用嵌套元组或HList的Slick的22列表? [英] How can I handle a > 22 column table with Slick using nested tuples or HLists?

问题描述

我是Scala(使用2.10)和Slick(使用2.0-M2)的新手.我看到在Slick中解决表的22列限制的一种方法是使用嵌套元组.尽管找到了在GitHub上的部分代码，我还是不知道该怎么做.

I'm new to Scala (using 2.10) and Slick (using 2.0-M2). I see that one of the ways to get around the 22 column limit for tables in Slick is to use nested tuples. I can't figure out how to do that, despite finding this partial code on GitHub.

当前的dev分支Scala(2.11-M5)支持包含22个以上元素的case类，但不支持Arity> 22的元组.Scala2.11预发行版尚未分发Slick.如何定义33列表(并使其与所有Slick的语法糖一起使用)?

Current dev branch Scala (2.11-M5) supports case classes with more than 22 elements, but not tuples with arity > 22. And Slick is not yet distributed for Scala 2.11 pre-releases. How can I define a 33 column table (and have it work with all Slick's syntactic sugar)?

N.B.，我正在尝试支持现有架构，并且无法更改表规范化.

N.B., I'm trying to support an existing schema and can't change the table normalization.

推荐答案

在这里，我写了一篇帖子给出解决方案.这是链接: https ://lihaimei.wordpress.com/2016/03/30/slick-1-fix-more-than-22-columns-case/

Here I write a post to give out the solution. Here is the link: https://lihaimei.wordpress.com/2016/03/30/slick-1-fix-more-than-22-columns-case/

我绘制一些图形并使用不同的颜色来帮助您快速理解.

I draw some graphs and use different colors to help you understand fast.

总而言之，我使用了额外的case类将某些列打包为一个，这不会影响实际的物理列.然后，当我们使用投影来映射到自定义类型时，我们会涉及到元组返回.这是一个hack解决方案，但是很容易解决Scala编程语言的限制，即元组的大小应小于22.

To summarize, I use additional case Class to package some columns to one, which will not influence real physical columns. And then when we use projection to map to a custom type, we involve tuple back. This is a hack solution, but it is easily to fix Scala programming language's limit where the size of tuples should be less than 22.

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