在Nodejs中解析大型JSON文件并独立处理每个对象

Question

我需要在Nodejs中读取一个大的JSON文件（大约630MB），并将每个对象插入MongoDB。

但是，答案是逐行处理JSON文件，而不是逐对象处理。因此，我仍然不知道如何从该文件中获取对象并对其进行操作。

我的JSON文件中大约有100,000种此类对象。

资料格式：

[
  {
    "id": "0000000",
    "name": "Donna Blak",
    "livingSuburb": "Tingalpa",
    "age": 53,
    "nearestHospital": "Royal Children's Hospital",
    "treatments": {
        "19890803": {
            "medicine": "Stomach flu B",
            "disease": "Stomach flu"
        },
        "19740112": {
            "medicine": "Progeria C",
            "disease": "Progeria"
        },
        "19830206": {
            "medicine": "Poliomyelitis B",
            "disease": "Poliomyelitis"
        }
    },
    "class": "patient"
  },
 ...
]

干杯，

Answer 1

有一个名为“ stream-json”的不错的模块，它可以完全满足您的需求。

它可以解析远远超出可用内存的JSON文件。

和

StreamArray处理一个频繁的用例：与Django生产的数据库转储类似的大量相对较小的对象。它逐个流处理阵列组件，并自动进行组装。

这是一个非常基本的示例：

const StreamArray = require('stream-json/streamers/StreamArray');

const path = require('path');

const fs = require('fs');



const jsonStream = StreamArray.withParser();



//You'll get json objects here

//Key is an array-index here

jsonStream.on('data', ({key, value}) => {

    console.log(key, value);

});



jsonStream.on('end', () => {

    console.log('All done');

});



const filename = path.join(__dirname, 'sample.json');

fs.createReadStream(filename).pipe(jsonStream.input);

如果您想做一些更复杂的事情，例如按顺序处理一个对象（保持顺序）并为每个对象应用一些异步操作，则可以执行以下自定义Writeable流：

const StreamArray = require('stream-json/streamers/StreamArray');

const {Writable} = require('stream');

const path = require('path');

const fs = require('fs');



const fileStream = fs.createReadStream(path.join(__dirname, 'sample.json'));

const jsonStream = StreamArray.withParser();



const processingStream = new Writable({

    write({key, value}, encoding, callback) {

        //Save to mongo or do any other async actions



        setTimeout(() => {

            console.log(value);

            //Next record will be read only current one is fully processed

            callback();

        }, 1000);

    },

    //Don't skip this, as we need to operate with objects, not buffers

    objectMode: true

});



//Pipe the streams as follows

fileStream.pipe(jsonStream.input);

jsonStream.pipe(processingStream);



//So we're waiting for the 'finish' event when everything is done.

processingStream.on('finish', () => console.log('All done'));

请注意： 以上示例已针对“ stream-json@1.1.3”进行了测试。对于某些以前的版本（可能早于1.0.0），您可能必须：

const StreamArray = require('stream-json/utils/StreamArray');

然后

const jsonStream = StreamArray.make();