问题描述

在 Slick 的文档中，提供了使用反应流的示例仅用于读取数据作为 DatabasePublisher 的一种方式.但是，当您想根据插入率将数据库用作 Sink 和 backpreasure 时会发生什么?

In Slick's documentation examples for using Reactive Streams are presented just for reading data as a means of a DatabasePublisher. But what happens when you want to use your database as a Sink and backpreasure based on your insertion rate?

我已经寻找了等效的DatabaseSubscriber，但它不存在.所以问题是，如果我有来源，请说:

I've looked for equivalent DatabaseSubscriber but it doesn't exist. So the question is, if I have a Source, say:

<代码>val 源 = 源(0 到 100)

我怎样才能用 Slick 构造一个 Sink 来将这些值写入一个带有模式的表中:

how can I crete a Sink with Slick that writes those values into a table with schema:

<代码>创建表 NumberTable(值 INT)

推荐答案

Serial Inserts

最简单的方法是在一个接收器.foreach.

The easiest way would be to do inserts within a Sink.foreach.

假设您已经使用了模式代码生成和进一步假设您的表名为NumberTable"

Assuming you've used the schema code generation and further assuming your table is named "NumberTable"

//Tables file was auto-generated by the schema code generation
import Tables.{Numbertable, NumbertableRow} 

val numberTableDB = Database forConfig "NumberTableConfig"

我们可以写一个函数来进行插入

We can write a function that does the insertion

def insertIntoDb(num : Int) = 
  numberTableDB run (Numbertable += NumbertableRow(num))

那个函数可以放在Sink中

And that function can be placed in the Sink

val insertSink = Sink[Int] foreach insertIntoDb

Source(0 to 100) runWith insertSink

批量插入

您可以通过一次批处理 N 个插入来进一步扩展 Sink 方法:

You could further extend the Sink methodology by batching N inserts at a time:

def batchInsertIntoDb(nums : Seq[Int]) = 
  numberTableDB run (Numbertable ++= nums.map(NumbertableRow.apply))

val batchInsertSink = Sink[Seq[Int]] foreach batchInsertIntoDb

这个批处理 Sink 可以由一个 Flow 提供，它进行批量分组:

This batched Sink can be fed by a Flow which does the batch grouping:

val batchSize = 10

Source(0 to 100).via(Flow[Int].grouped(batchSize))
                .runWith(batchInsertSink)

这篇关于Slick 中如何使用反应流来插入数据的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持跟版网！