Command StdinPipe closes too soon - postgresql

Question

I've been trying to call pg_restore using exec.Command and feed StdinPipe with data from database dump file, it works with small files under 1Mb but it fails for bigger dumps with the write |1: broken pipe error. I also tried to scan line by line and write to pipe but it resulted in the same error and running like cmd.Run() in separate goroutine didn't help either.
Go: 1.14
OS: macOS
cmd := exec.Command("pg_restore", "--clean", "-n public", "--dbname=DB_URI")
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr
pw, err := cmd.StdinPipe()
defer pw.Close()
...
done := make(chan struct{})
errCh := make(chan error)
file, err := os.Open("dumpfile")
defer file.Close()
if err := cmd.Start(); err != nil {
return err
}
_, err = io.Copy(pw, file)
What am I doing wrong or how to keep pipe open?

Answer 1

When using cat instead of pg_restore, your code works.
When using head -10, on the other hand, I hit the same error as you, which is actually expected.
Since you are starting your cmd in async mode, if pg_restore halts before consuming all of its STDIN, io.Copy will hit this kind of error if it tries to write on a closed pipe.
Check the state of your pg_restore command (final return code, content printed on its STDERR, logs ...) to see if there is an actual error.
You can treat this error as a normal indication that you shouldn't feed input to this command anymore.

Answer 2

including cmd.Wait() should solve your problem, like it says int one of your comments.

Answer 3

With the help of my colleague we found that command arguments were malformed, since Go directly uses syscalls each argument of a program must be separate so here
-n public was leading to the issue
"pg_restore", "--clean", "-n public", "--dbname=DB_URI"
and the fix quite clear as well – split them -n, public
"pg_restore", "--clean", "-n", "public", "--dbname=DB_URI"