Dump Mongo Collection into JSON format - json

Question

Is there any way to dump mongo collection into json format? Either on the shell or using java driver.I am looking for the one with best performance.

Answer 1

Mongo includes a mongoexport utility (see docs) which can dump a collection. This utility uses the native libmongoclient and is likely the fastest method.
mongoexport -d <database> -c <collection_name>
Also helpful:
-o: write the output to file, otherwise standard output is used (docs)
--jsonArray: generates a valid json document, instead of one json object per line (docs)
--pretty: outputs formatted json (docs)

Answer 2

Use mongoexport/mongoimport to dump/restore a collection:
Export JSON File:
mongoexport --db <database-name> --collection <collection-name> --out output.json
Import JSON File:
mongoimport --db <database-name> --collection <collection-name> --file input.json
WARNING
mongoimport and mongoexport do not reliably preserve all rich BSON data types because JSON can only represent a subset of the types supported by BSON. As a result, data exported or imported with these tools may lose some measure of fidelity.
Also, http://bsonspec.org/
BSON is designed to be fast to encode and decode. For example,
integers are stored as 32 (or 64) bit integers, so they don't need to
be parsed to and from text. This uses more space than JSON for small
integers, but is much faster to parse.
In addition to compactness, BSON adds additional data types
unavailable in JSON, notably the BinData and Date data types.

Answer 3

Here's mine command for reference:
mongoexport --db AppDB --collection files --pretty --out output.json
On Windows 7 (MongoDB 3.4), one has to move the cmd to the place where mongod.exe and mongo.exe file resides =>
C:\MongoDB\Server\3.4\bin else it won't work saying it does not recongnize mongoexport command.

Answer 4

From the Mongo documentation:
The mongoexport utility takes a collection and exports to either JSON or CSV. You can specify a filter for the query, or a list of fields to output
Read more here: http://www.mongodb.org/display/DOCS/mongoexport

Answer 5

Here is a little node script that I write to dump all collections in a specific database to the specified output directory...
#!/usr/bin/env node
import { MongoClient } from 'mongodb';
import { spawn } from 'child_process';
import fs from 'fs';
const DB_URI = 'mongodb://0.0.0.0:27017';
const DB_NAME = 'database-name';
const OUTPUT_DIR = 'output-directory';
const client = new MongoClient(DB_URI);
async function run() {
try {
await client.connect();
const db = client.db(DB_NAME);
const collections = await db.collections();
if (!fs.existsSync(OUTPUT_DIR)) {
fs.mkdirSync(OUTPUT_DIR);
}
collections.forEach(async (c) => {
const name = c.collectionName;
await spawn('mongoexport', [
'--db',
DB_NAME,
'--collection',
name,
'--jsonArray',
'--pretty',
`--out=./${OUTPUT_DIR}/${name}.json`,
]);
});
} finally {
await client.close();
console.log(`DB Data for ${DB_NAME} has been written to ./${OUTPUT_DIR}/`);
}
}
run().catch(console.dir);