[英]node.js pg-promise and pagination from API
Looking at https://github.com/vitaly-t/pg-promise/wiki/Data-Imports there's a very detailed doc on how to use it for importing. 看看https://github.com/vitaly-t/pg-promise/wiki/Data-Imports,有一个关于如何使用它进行导入的非常详细的文档。
However while that works for the demoed scenario I don't know how to apply it on my case. 然而,虽然这适用于演示场景,但我不知道如何将其应用于我的案例。
When I do my web call, I get the actual JSON data and a paramter in the header which gives me a value for the next page (could be a date or String or a number value). 当我进行网络调用时,我会在标题中获得实际的JSON数据和参数,它为下一页提供了一个值(可以是日期或字符串或数字值)。
In the example, it says: 在示例中,它说:
db.tx('massive-insert', t => {
return t.sequence(index => {
return getNextData(index)
.then(data => {
if (data) {
const insert = pgp.helpers.insert(data, cs);
return t.none(insert);
}
});
});
})
.then(data => {
console.log('Total batches:', data.total, ', Duration:', data.duration);
})
.catch(error => {
console.log(error);
});
In this case, sequence(index
will use index which seems to increment +1. But in my case, 在这种情况下,
sequence(index
将使用似乎增加+1的索引。但在我的情况下,
function getNextData(nextPage) {
//get the data for nextPage
.....
//get the nextPage if exists for future use
nextPage = response.next;
resolve(data);
}
My question is, how can I replace index
with nextPage
in this example, as each new Promise needs to use the nextPage
from previous one. 我的问题是,如何在这个例子中用
nextPage
替换index
,因为每个新的Promise需要使用前一个的nextPage
。
LATER EDIT: And if I want to fetch info from a certain value of nextPageInfo? LATER EDIT:如果我想从nextPageInfo的某个值获取信息?
For instance: 例如:
db.any('Select value from table')
.then(function(value) {
var data = value; //not working
db.tx('massive-insert', t => {
return t.sequence((index, data) => {
return getNextData(index, data)
.then(a => {
if (a) {
const insert = pgp.helpers.insert(a.data, cs);
return t.none(insert).then(() => a.nextPageInfo);
}
})
});
})
.then(data => {
// COMMIT has been executed
console.log('Total batches:', data.total, ', Duration:', data.duration);
})
.catch(error => {
// ROLLBACK has been executed
console.log(error);
})
}
Following this question, I have extended article Data Imports with the new extras section, which gives you exactly the example that you need. 在这个问题之后,我已经使用新的附加部分扩展了文章Data Imports ,它为您提供了所需的示例。 The example copied from the article:
从文章中复制的示例:
function getNextData(t, index, nextPageInfo) {
// t = database transaction protocol
// NOTE: nextPageInfo = undefined when index = 0
return new Promise((resolve, reject) {
/* pull the next data, according to nextPageInfo */
/* do reject(error) on an error, to ROLLBACK changes */
if(/* there is still data left*/) {
// if whateverNextDetails = undefined, the data will be inserted,
// but the sequence will end there (as success).
resolve({data, nextPageInfo: whateverNextDetails});
} else {
resolve(null);
}
});
}
db.tx('massive-insert', t => {
return t.sequence((index, data) => {
return getNextData(t, index, data)
.then(a => {
if (a) {
const insert = pgp.helpers.insert(a.data, cs);
return t.none(insert).then(() => a.nextPageInfo);
}
})
});
})
.then(data => {
// COMMIT has been executed
console.log('Total batches:', data.total, ', Duration:', data.duration);
})
.catch(error => {
// ROLLBACK has been executed
console.log(error);
});
Please note that since we are chaining the result from getNextData
to the value of nextPageInfo
, then if its value is undefined
, it will do the next insert, but then will end the sequence (as success). 请注意,因为我们将
getNextData
的结果链接到nextPageInfo
的值,所以如果它的值undefined
,它将执行下一次插入,但随后将结束序列(成功)。
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