Copy stream hangs if using gzip stream compression

[uasan]

Hello, we caught a cool bug )

Streams work fine when copying, but if the stream is sent to the compression pipe, the entire pool of connections freezes.

Example, playback:

import postgres from 'postgres';
import { createGzip } from 'zlib';

const db = postgres({
  max: 2,
});

for (let i = 0; i < 10; i++) {
  let stream = await db
    .unsafe(`COPY pg_catalog.pg_attribute TO STDOUT`)
    .readable();

  stream.pipe(createGzip()).on('data', console.log);

  await db.unsafe(`SELECT $1 AS "CONTINUE"`, [i]);
}

console.log(await db.unsafe(`SELECT 'DONE' AS "END"`));

I play with pipe, but in any case, something is wrong with the connection pool after sending the stream to the pipe.

[uasan]

It seems that this problem was the cause of the connection errors that I described here #457. Due to the pipe, connections in the pool become busy in read mode, although postgres has returned the response and there is nothing to read

[porsager]

Sorry I haven't been on this @uasan .. I can repro here, so I hope I'll find some time to look into it soon!

[uasan]

I think this is due to the fact that the archiving stream sometimes pauses the stream

[Ivor808]

I wonder if I am hitting a similar issue. Certain copy commands are read to stdout into a readable stream. Those readable streams sometimes just hang and it seems as if the "end" event is never transmitted.