Pg-promise - How to stream binary data directly to response - pg-promise

Question

Forgive me I'm still learning. I'm trying to download some mp3 files that I have stored in a table. I can download files directly from the file system like this:
if (fs.existsSync(filename)) {
res.setHeader('Content-disposition', 'attachment; filename=' + filename);
res.setHeader('Content-Type', 'application/audio/mpeg3');
var rstream = fs.createReadStream(filename);
rstream.pipe(res);
I have stored the data in the table using pg-promise example in the docs like so:
const rs = fs.createReadStream(filename);
function receiver(_, data) {
function source(index) {
if (index < data.length) {
return data[index];
}
}
function dest(index, data) {
return this.none('INSERT INTO test_bin (utterance) VALUES($1)', data);
}
return this.sequence(source, {dest});
} // end receiver func
rep.tx(t => {
return streamRead.call(t, rs, receiver);
})
.then(data => {
console.log('DATA:', data);
})
.catch(error => {
console.log('ERROR: ', error);
});
But now I want to take that data out of the table and download it to the client. The example in the docs of taking data out of binary converts it to JSON and then prints it to the console like this:
db.stream(qs, s => {
s.pipe(JSONStream.stringify()).pipe(process.stdout)
})
and that works. So the data is coming out of the database ok. But I can't seem to send it to the client. It seems that the data is already a stream so I have tried:
db.stream(qs, s => {
s.pipe(res);
});
But I get a typeerror: First argument must be a string or Buffer
Alternatively, I could take that stream and write it to the file system, and then serve it as in the top step above, but that seems like a workaround. I wish there was an example of how to save to a file in the docs.
What step am I missing?