API to upload file as BLOB without preallocation

[mcpiroman]

Hi, is there any API to load file (or other stream data) without loading it entirely to memory?

Right now I do:

let mut file = File::open(&schema_file.path)?;
let mut blob = Blob::new(&conn)?;
io::copy(&mut file, &mut blob)?;
stmt.execute(&[&blob])?;

for comparison, jdbc has

void setBlob(int parameterIndex, InputStream inputStream)

[kubo]

is there any API to load file (or other stream data) without loading it entirely to memory?

Yes. Your example sends file contents to the server for each Blob::write inside of io::copy.

Blob::write internally calls dpiLob_writeBytes, which requires network round-trips as listed here. If Blob::write stores bytes to memory, no round-trips are required.

[mcpiroman]

OK, so that's why Blob::new requires &connection. I did not think that was the case as I not expect anything to be sent before execute.

Anyway, big thanks.

[kubo]

io::copy uses 8K buffer for non-specialized implementation. I think that it is too small for network I/O. It is better to use BufWriter::with_capacity() to increase the size.

let buffer_size = 1024 * 1024; // This is by guesswork. The proper size depends on the network environment.
let mut file = File::open(&schema_file.path)?;
let mut blob = BufWriter::with_capacity(buffer_size, Blob::new(&conn)?);
io::copy(&mut file, &mut blob)?;
blob.flush()?; // Don't forget this.
stmt.execute(&[blob.get_ref()])?;