Receive result rows from pg as a readable (object) stream.
$ npm install pg --save
$ npm install pg-query-stream --saverequires pg>=2.8.1
const pg = require('pg')
var pool = new pg.Pool()
const QueryStream = require('pg-query-stream')
const JSONStream = require('JSONStream')
//pipe 1,000,000 rows to stdout without blowing up your memory usage
pool.connect((err, client, done) => {
if (err) throw err
const query = new QueryStream('SELECT * FROM generate_series(0, $1) num', [1000000])
const stream = client.query(query)
//release the client when the stream is finished
stream.on('end', done)
stream.pipe(JSONStream.stringify()).pipe(process.stdout)
})The stream uses a cursor on the server so it efficiently keeps only a low number of rows in memory.
This is especially useful when doing ETL on a huge table. Using manual limit and offset queries to fake out async itteration through your data is cumbersome, and way way way slower than using a cursor.
note: this module only works with the JavaScript client, and does not work with the native bindings. libpq doesn't expose the protocol at a level where a cursor can be manipulated directly
I'm very open to contribution! Open a pull request with your code or idea and we'll talk about it. If it's not way insane we'll merge it in too: isn't open source awesome?
The MIT License (MIT)
Copyright (c) 2013-2020 Brian M. Carlson
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