pg-promise transaction with dependent queries in forEach loop gives warning Error: Querying against a released or lost connection

Question

我正在尝试在 pg-promise 事务中插入链接数据。事务成功插入所有数据正确，但给出警告UnhandledPromiseRejectionWarning: Error: Querying against a released or lost connection.。

导致这个的代码原来是：

const item = {
  batch: { batch_number: 1 },
  ingredients: [
    { amount: '12', unit: 'kg' },
    { amount: '4', unit: 'L' }
  ],
}


return await db.tx(async t => {
  const batchQueryString = pgp.helpers.insert(item.batch, null, 'ionomer_batch')
  const batchQuery = await t.one(batchQueryString + ' RETURNING ionomer_batch_id')

  item.ingredients.forEach(async ingredient => {
    const ingredientQueryString = pgp.helpers.insert(ingredient, null, 'ingredient')
    const ingredientQuery = await t.one(ingredientQueryString + ' RETURNING ingredient_id')
    await t.none(
            `INSERT INTO ionomer_batch_step(ionomer_batch_id, ingredient_id) 
            VALUES(${batchQuery.ionomer_batch_id}, ${ingredientQuery.ingredient_id})`
            )
   })

   return batchQuery
  }).then(data => {
    return {success: true, response: data}
  }).catch(error => {
    return {success: false, response: error}
})

我通过

让它在没有产生警告的情况下工作

return await db.tx(async t => {
  const batchQueryString = pgp.helpers.insert(item.batch, null, 'ionomer_batch')
  const batchQuery = await t.one(batchQueryString + ' RETURNING ionomer_batch_id')

  const ingredientQueries = []
  // this can't be async
  item.ingredients.forEach(ingredient => {
    const ingredientQueryString = pgp.helpers.insert(ingredient, null, 'ingredient')
    const ingredientQuery = t.one(ingredientQueryString + ' RETURNING ingredient_id')
    ingredientQueries.push(ingredientQuery)
   })
   const resolvedIngredientQueries = await t.batch(ingredientQueries)
   resolvedIngredientQueries.forEach(async ingredientQuery => {
     await t.none(
       `INSERT INTO ionomer_batch_step(ionomer_batch_id, ingredient_id) 
       VALUES(${batchQuery.ionomer_batch_id}, ${ingredientQuery.ingredient_id})`
      )
    })

   return batchQuery
  }).then(data => {
    return {success: true, response: data}
  }).catch(error => {
    return {success: false, response: error}
})

但我现在必须循环两次而不是一次，而且我在第一个循环中失去了异步。似乎应该有一种方法可以在接近第一次尝试时做一些事情，而不会发出有关已释放或丢失连接的警告。我试着链接查询，但无法让它工作。

Answer 1

正如@vitaly-t 所说，我需要确保 forEach 循环真正完成。

可行的解决方案是

const item = {
  batch_number: 1,
  },
  ingredients: [
    { amount: '12', unit: 'kg' },
    { amount: '4', unit: 'L' }
  ],
}


return await db.tx(async t => {
  const batchQueryString = pgp.helpers.insert(item.batch, null, 'ionomer_batch')
  const batchQuery = await t.one(batchQueryString + ' RETURNING ionomer_batch_id')

  await asyncForEach(item.ingredients, async ingredient => {
    const ingredientQueryString = pgp.helpers.insert(ingredient, null, 'ingredient')
    const ingredientQuery = await t.one(ingredientQueryString + ' RETURNING ingredient_id')
    await t.none(
            `INSERT INTO ionomer_batch_step(ionomer_batch_id, ingredient_id) 
            VALUES(${batchQuery.ionomer_batch_id}, ${ingredientQuery.ingredient_id})`
            )
   })

   return batchQuery
  }).then(data => {
    return {success: true, response: data}
  }).catch(error => {
    return {success: false, response: error}
})

我必须在哪里创建辅助函数

async function asyncForEach(array, callback) {
  for (let index = 0; index < array.length; index++) {
    await callback(array[index], index, array);
  }
}

如描述here

Answer 2

作为对@deanna 自己回答的补充...

你真的不需要实现循环。您可以将请求重新映射到承诺数组中，然后解决它：

await db.tx(async t => {
    const batchQueryString = pgp.helpers.insert(item.batch, null, 'ionomer_batch');
    const batchQuery = await t.one(`${batchQueryString} RETURNING ionomer_batch_id`);

    const inserts = item.ingredients.map(async i => {
        const query = pgp.helpers.insert(i, null, 'ingredient');
        const ingredientQuery = await t.one(`${query} RETURNING ingredient_id`);
        return t.none(
            `INSERT INTO ionomer_batch_step(ionomer_batch_id, ingredient_id)
            VALUES($/batchQuery.ionomer_batch_id/, $/ingredientQuery.ingredient_id/)`,
            {batchQuery, ingredientQuery});
   });

    await t.batch(inserts); // settle all generated promises

    return batchQuery;
});

另外，你可以从变化中看出，你不应该那样使用 ES6 值注入。 See here:

IMPORTANT: Never use the reserved ${} syntax inside ES6 template strings, as those have no knowledge of how to format values for PostgreSQL. Inside ES6 template strings you should only use one of the 4 alternatives - $(), $<>, $[] or $//.

pg-promise transaction with dependent queries in forEach loop gives warning Error: Querying against a released or lost connection

pg-promise transaction with dependent queries in forEach loop gives warning Error: Querying against a released or lost connection

javascript

node.js

transactions

pg-promise