如何循环遍历多行 sql 查询并在 Knex Transactions 中使用它们？

Question

Node 和 Knex 的新手来自 RoR 背景，我需要将特定函数转换为 Node.js

这是我的 RoR 代码：

  def self.save!
    update_queries = self.fetch.map{|currency, rate|
      "UPDATE currency_exchange_rates SET rate='#{rate}' WHERE currency='#{currency}'"
    }.join(';')

    ActiveRecord::Base.connection.execute(update_queries)
  end

到目前为止，这是我在 Nodejs 中所拥有的：

static save(new_rates){
      return new Promise(async (resolve, reject) => {
        var query = Object.keys(rate).map(key => 'UPDATE currency_exchange_rates SET rate=' + rate[key] + ' WHERE currency = "' + key + '"').join('; ');
    })
  }

输入数据如下所示：

新价格 =

'UPDATE currency_exchange_rates SET rate=32102793.12 WHERE currency= "IDR"; 

UPDATE currency_exchange_rates SET rate=0.7822 WHERE currency= "USDGBP"; 

UPDATE currency_exchange_rates SET rate=3189.756317 WHERE currency= "CAD"; 

UPDATE currency_exchange_rates SET rate=152.8 WHERE currency= "USDLKR"; 

UPDATE currency_exchange_rates SET rate=110.818 WHERE currency= "USDJPY"; 

UPDATE currency_exchange_rates SET rate=1.3103 WHERE currency= "USDAUD"'

我正在使用Knex.js 连接到我的 pg 数据库。如何使用 knex 执行所有这些操作？我可以通过knex.raw() 中的所有查询吗？ knex.transaction() 怎么样？它们有什么区别？

提前致谢！

Answer 1

// [Sequential Update] Commit transaction after each successfully executed query
await knex.transaction(async trx => {
    return Promise.all(Object.keys(rate).map(key => trx('currency_exchange_rates')
            .update({ rate: rate[key] })
            .where({ currency: key })
    ));
});

// [Bulk Update] Commit transaction after all queries have been executed successfully
await knex.transaction(trx => {
    return Promise.all(Object.keys(rate).map(key => knex('currency_exchange_rates')
            .update({ rate: rate[key] })
            .where({ currency: key })
        ))
        .then(trx.commit)
        .catch(trx.rollback);
});

Answer 2

这样的做法很巧妙：

let retVal = await knex.transaction(async (trx) => {
  for (let key of Object.keys(rate)) {
    let value = rate[key];
    await trx('currency_exchange_rates')
      .update({ rate: value }).where('currency', key);
  }
  return "woo done"; // this value is returned from transaction 
});

在处理事务时，通常希望在通过事务的单个 DB 连接运行查询之前，一个一个地创建和运行查询，以避免不必要的查询缓冲。