Scala+Slick 3:将一个查询的结果插入到另一个表中 [英] Scala+Slick 3: Inserting the result of one query into another table

问题描述

这个问题是关于 slick 3.0 或 3.1(我对此很灵活)

This question is about slick 3.0 or 3.1 (I am flexible about that)

我有一个中间查询，我使用 map、for 等处理该查询以获得我想要的结果.最后我有一个

I have an intermediate query which I process with map, for, etc. to obtain the result I want. In the end I have a

val foo: DBIOAction[Seq[MySchema.Bar], NoStream, Effect.Read]

现在我有一个 val bar: TableQuery[MySchema.Bar] 并且我想在其中插入 foo.

Now I have a val bar: TableQuery[MySchema.Bar] and I want to insert foo in to it.

如果 foo 是 Seq 我可以简单地做 bar ++= foo，但它不是.

If foo would be a Seq I could simply do bar ++= foo, but it is not.

我发现的唯一方法是通过等待来实现结果.像这样

The only way I found is to materialize the result by awaiting it. Like this

val query = (bar ++= Await.result(db.run(foo), Duration.Inf))

显然query 需要在某个时候使用db.run 运行.但现在我有两个数据库运行.一次性完成所有内容不是更好吗?

Obviously query needs to be run at some point with db.run. But now I have two DB-runs. Wouldn't it be better to have everything in a single run?

有没有更好的方法来做到这一点?

推荐答案

DBIOAction 有 map/flatMap 函数，所以你可以写点东西喜欢

DBIOAction has map/flatMap functions, so you can write something like

val insertAction = foo.flatMap(bar ++= _)

insertAction 将是 DBIOAction[Int, NoStream, Effect.Write] 或类似的类型(我不完全确定 Int 和效果)，然后您可以使用 db.run 将它作为任何 DBIOAction 在数据库上运行；然后你得到的是整个查询和插入结果的未来.

The insertAction will be of type DBIOAction[Int, NoStream, Effect.Write] or something like that (I'm not entirely sure about Int and the effect), then you can run it on the DB as any DBIOAction using db.run; what you then get is a future of the overall query and insert result.

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